proc文件系统介绍

Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
..............................................................................
Field Content
pid process id
tcomm filename of the executable
state state (R is running, S is sleeping, D is sleeping in an
uninterruptible wait, Z is zombie, T is traced or stopped)
ppid process id of the parent process
pgrp pgrp of the process
sid session id
tty_nr tty the process uses
tty_pgrp pgrp of the tty
flags task flags
min_flt number of minor faults
cmin_flt number of minor faults with child's
maj_flt number of major faults
cmaj_flt number of major faults with child's
utime user mode jiffies
stime kernel mode jiffies
cutime user mode jiffies with child's
cstime kernel mode jiffies with child's
priority priority level
nice nice level
num_threads number of threads
it_real_value (obsolete, always 0)
start_time time the process started after system boot
vsize virtual memory size
rss resident set memory size
rsslim current limit in bytes on the rss
start_code address above which program text can run
end_code address below which program text can run
start_stack address of the start of the main process stack
esp current value of ESP
eip current value of EIP
pending bitmap of pending signals
blocked bitmap of blocked signals
sigign bitmap of ignored signals
sigcatch bitmap of catched signals
wchan address where process went to sleep
0 (place holder)
0 (place holder)
exit_signal signal to send to parent thread on exit
task_cpu which CPU the task is scheduled on
rt_priority realtime priority
policy scheduling policy (man sched_setscheduler)
blkio_ticks time spent waiting for block IO
gtime guest time of the task in jiffies
cgtime guest time of the task children in jiffies
start_data address above which program data+bss is placed
end_data address below which program data+bss is placed
start_brk address above which program heap can be expanded with brk()
arg_start address above which program command line is placed
arg_end address below which program command line is placed
env_start address above which program environment is placed
env_end address below which program environment is placed
exit_code the thread's exit_code in the form reported by the waitpid system call
..............................................................................

------------------------------------------------------------------------------
T H E  /proc   F I L E S Y S T E M
------------------------------------------------------------------------------
/proc/sys         Terrehon Bowden <terrehon@pacbell.net>        October 7 1999
Bodo Bauer <bb@ricochet.net>

2.4.x update	  Jorge Nerin <comandante@zaralinux.com>      November 14 2000
move /proc/sys	  Shen Feng <shen@cn.fujitsu.com>		  April 1 2009
------------------------------------------------------------------------------
Version 1.3                                              Kernel version 2.2.12
Kernel version 2.4.0-test11-pre4
------------------------------------------------------------------------------
fixes/update part 1.1  Stefani Seibold <stefani@seibold.net>       June 9 2009

Table of Contents
-----------------

0     Preface
0.1	Introduction/Credits
0.2	Legal Stuff

1	Collecting System Information
1.1	Process-Specific Subdirectories
1.2	Kernel data
1.3	IDE devices in /proc/ide
1.4	Networking info in /proc/net
1.5	SCSI info
1.6	Parallel port info in /proc/parport
1.7	TTY info in /proc/tty
1.8	Miscellaneous kernel statistics in /proc/stat
1.9 Ext4 file system parameters

2	Modifying System Parameters

3	Per-Process Parameters
3.1	/proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
score
3.2	/proc/<pid>/oom_score - Display current oom-killer score
3.3	/proc/<pid>/io - Display the IO accounting fields
3.4	/proc/<pid>/coredump_filter - Core dump filtering settings
3.5	/proc/<pid>/mountinfo - Information about mounts
3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
3.7   /proc/<pid>/task/<tid>/children - Information about task children
3.8   /proc/<pid>/fdinfo/<fd> - Information about opened file

4	Configuring procfs
4.1	Mount options

------------------------------------------------------------------------------
Preface
------------------------------------------------------------------------------

0.1 Introduction/Credits
------------------------

This documentation is  part of a soon (or  so we hope) to be  released book on
the SuSE  Linux distribution. As  there is  no complete documentation  for the
/proc file system and we've used  many freely available sources to write these
chapters, it  seems only fair  to give the work  back to the  Linux community.
This work is  based on the 2.2.*  kernel version and the  upcoming 2.4.*. I'm
afraid it's still far from complete, but we  hope it will be useful. As far as
we know, it is the first 'all-in-one' document about the /proc file system. It
is focused  on the Intel  x86 hardware,  so if you  are looking for  PPC, ARM,
SPARC, AXP, etc., features, you probably  won't find what you are looking for.
It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
additions and patches  are welcome and will  be added to this  document if you
mail them to Bodo.

We'd like  to  thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
other people for help compiling this documentation. We'd also like to extend a
special thank  you to Andi Kleen for documentation, which we relied on heavily
to create  this  document,  as well as the additional information he provided.
Thanks to  everybody  else  who contributed source or docs to the Linux kernel
and helped create a great piece of software... :)

If you  have  any comments, corrections or additions, please don't hesitate to
contact Bodo  Bauer  at  bb@ricochet.net.  We'll  be happy to add them to this
document.

The   latest   version    of   this   document   is    available   online   at http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html 
If  the above  direction does  not works  for you,  you could  try the  kernel
mailing  list  at  linux-kernel@vger.kernel.org  and/or try  to  reach  me  at
comandante@zaralinux.com.

0.2 Legal Stuff
---------------

We don't  guarantee  the  correctness  of this document, and if you come to us
complaining about  how  you  screwed  up  your  system  because  of  incorrect
documentation, we won't feel responsible...

------------------------------------------------------------------------------
CHAPTER 1: COLLECTING SYSTEM INFORMATION
------------------------------------------------------------------------------

------------------------------------------------------------------------------
In This Chapter
------------------------------------------------------------------------------
* Investigating  the  properties  of  the  pseudo  file  system  /proc and its
ability to provide information on the running Linux system
* Examining /proc's structure
* Uncovering  various  information  about the kernel and the processes running
on the system
------------------------------------------------------------------------------

The proc  file  system acts as an interface to internal data structures in the
kernel. It  can  be  used to obtain information about the system and to change
certain kernel parameters at runtime (sysctl).

First, we'll  take  a  look  at the read-only parts of /proc. In Chapter 2, we
show you how you can use /proc/sys to change settings.

1.1 Process-Specific Subdirectories
-----------------------------------

The directory  /proc  contains  (among other things) one subdirectory for each
process running on the system, which is named after the process ID (PID).

The link  self  points  to  the  process reading the file system. Each process
subdirectory has the entries listed in Table 1-1.

Table 1-1: Process specific entries in /proc
..............................................................................
File		Content
clear_refs	Clears page referenced bits shown in smaps output
cmdline	Command line arguments
cpu		Current and last cpu in which it was executed	(2.4)(smp)
cwd		Link to the current working directory
environ	Values of environment variables
exe		Link to the executable of this process
fd		Directory, which contains all file descriptors
maps		Memory maps to executables and library files	(2.4)
mem		Memory held by this process
root		Link to the root directory of this process
stat		Process status
statm		Process memory status information
status		Process status in human readable form
wchan		If CONFIG_KALLSYMS is set, a pre-decoded wchan
pagemap	Page table
stack		Report full stack trace, enable via CONFIG_STACKTRACE
smaps		a extension based on maps, showing the memory consumption of
each mapping and flags associated with it
..............................................................................

For example, to get the status information of a process, all you have to do is
read the file /proc/PID/status:

>cat /proc/self/status
Name:   cat
State:  R (running)
Tgid:   5452
Pid:    5452
PPid:   743
TracerPid:      0						(2.4)
Uid:    501     501     501     501
Gid:    100     100     100     100
FDSize: 256
Groups: 100 14 16
VmPeak:     5004 kB
VmSize:     5004 kB
VmLck:         0 kB
VmHWM:       476 kB
VmRSS:       476 kB
VmData:      156 kB
VmStk:        88 kB
VmExe:        68 kB
VmLib:      1412 kB
VmPTE:        20 kb
VmSwap:        0 kB
Threads:        1
SigQ:   0/28578
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 00000000fffffeff
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
Seccomp:        0
voluntary_ctxt_switches:        0
nonvoluntary_ctxt_switches:     1

This shows you nearly the same information you would get if you viewed it with
the ps  command.  In  fact,  ps  uses  the  proc  file  system  to  obtain its
information.  But you get a more detailed  view of the  process by reading the
file /proc/PID/status. It fields are described in table 1-2.

The  statm  file  contains  more  detailed  information about the process
memory usage. Its seven fields are explained in Table 1-3.  The stat file
contains details information about the process itself.  Its fields are
explained in Table 1-4.

(for SMP CONFIG users)
For making accounting scalable, RSS related information are handled in
asynchronous manner and the vaule may not be very precise. To see a precise
snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
It's slow but very precise.

Table 1-2: Contents of the status files (as of 2.6.30-rc7)
..............................................................................
Field                       Content
Name                        filename of the executable
State                       state (R is running, S is sleeping, D is sleeping
in an uninterruptible wait, Z is zombie,
T is traced or stopped)
Tgid                        thread group ID
Pid                         process id
PPid                        process id of the parent process
TracerPid                   PID of process tracing this process (0 if not)
Uid                         Real, effective, saved set, and  file system UIDs
Gid                         Real, effective, saved set, and  file system GIDs
FDSize                      number of file descriptor slots currently allocated
Groups                      supplementary group list
VmPeak                      peak virtual memory size
VmSize                      total program size
VmLck                       locked memory size
VmHWM                       peak resident set size ("high water mark")
VmRSS                       size of memory portions
VmData                      size of data, stack, and text segments
VmStk                       size of data, stack, and text segments
VmExe                       size of text segment
VmLib                       size of shared library code
VmPTE                       size of page table entries
VmSwap                      size of swap usage (the number of referred swapents)
Threads                     number of threads
SigQ                        number of signals queued/max. number for queue
SigPnd                      bitmap of pending signals for the thread
ShdPnd                      bitmap of shared pending signals for the process
SigBlk                      bitmap of blocked signals
SigIgn                      bitmap of ignored signals
SigCgt                      bitmap of catched signals
CapInh                      bitmap of inheritable capabilities
CapPrm                      bitmap of permitted capabilities
CapEff                      bitmap of effective capabilities
CapBnd                      bitmap of capabilities bounding set
Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
Cpus_allowed                mask of CPUs on which this process may run
Cpus_allowed_list           Same as previous, but in "list format"
Mems_allowed                mask of memory nodes allowed to this process
Mems_allowed_list           Same as previous, but in "list format"
voluntary_ctxt_switches     number of voluntary context switches
nonvoluntary_ctxt_switches  number of non voluntary context switches
..............................................................................

Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
..............................................................................
Field    Content
size     total program size (pages)		(same as VmSize in status)
resident size of memory portions (pages)	(same as VmRSS in status)
shared   number of pages that are shared	(i.e. backed by a file)
trs      number of pages that are 'code'	(not including libs; broken,
includes data segment)
lrs      number of pages of library		(always 0 on 2.6)
drs      number of pages of data/stack		(including libs; broken,
includes library text)
dt       number of dirty pages			(always 0 on 2.6)
..............................................................................

Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
..............................................................................
Field          Content
pid           process id
tcomm         filename of the executable
state         state (R is running, S is sleeping, D is sleeping in an
uninterruptible wait, Z is zombie, T is traced or stopped)
ppid          process id of the parent process
pgrp          pgrp of the process
sid           session id
tty_nr        tty the process uses
tty_pgrp      pgrp of the tty
flags         task flags
min_flt       number of minor faults
cmin_flt      number of minor faults with child's
maj_flt       number of major faults
cmaj_flt      number of major faults with child's
utime         user mode jiffies
stime         kernel mode jiffies
cutime        user mode jiffies with child's
cstime        kernel mode jiffies with child's
priority      priority level
nice          nice level
num_threads   number of threads
it_real_value	(obsolete, always 0)
start_time    time the process started after system boot
vsize         virtual memory size
rss           resident set memory size
rsslim        current limit in bytes on the rss
start_code    address above which program text can run
end_code      address below which program text can run
start_stack   address of the start of the main process stack
esp           current value of ESP
eip           current value of EIP
pending       bitmap of pending signals
blocked       bitmap of blocked signals
sigign        bitmap of ignored signals
sigcatch      bitmap of catched signals
wchan         address where process went to sleep
0             (place holder)
0             (place holder)
exit_signal   signal to send to parent thread on exit
task_cpu      which CPU the task is scheduled on
rt_priority   realtime priority
policy        scheduling policy (man sched_setscheduler)
blkio_ticks   time spent waiting for block IO
gtime         guest time of the task in jiffies
cgtime        guest time of the task children in jiffies
start_data    address above which program data+bss is placed
end_data      address below which program data+bss is placed
start_brk     address above which program heap can be expanded with brk()
arg_start     address above which program command line is placed
arg_end       address below which program command line is placed
env_start     address above which program environment is placed
env_end       address below which program environment is placed
exit_code     the thread's exit_code in the form reported by the waitpid system call
..............................................................................

The /proc/PID/maps file containing the currently mapped memory regions and
their access permissions.

The format is:

address           perms offset  dev   inode      pathname

08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
a7cb1000-a7cb2000 ---p 00000000 00:00 0
a7cb2000-a7eb2000 rw-p 00000000 00:00 0
a7eb2000-a7eb3000 ---p 00000000 00:00 0
a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack:1001]
a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
a800b000-a800e000 rw-p 00000000 00:00 0
a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
a8024000-a8027000 rw-p 00000000 00:00 0
a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
aff35000-aff4a000 rw-p 00000000 00:00 0          [stack]
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

where "address" is the address space in the process that it occupies, "perms"
is a set of permissions:

r = read
w = write
x = execute
s = shared
p = private (copy on write)

"offset" is the offset into the mapping, "dev" is the device (major:minor), and
"inode" is the inode  on that device.  0 indicates that  no inode is associated
with the memory region, as the case would be with BSS (uninitialized data).
The "pathname" shows the name associated file for this mapping.  If the mapping
is not associated with a file:

[heap]                   = the heap of the program
[stack]                  = the stack of the main process
[stack:1001]             = the stack of the thread with tid 1001
[vdso]                   = the "virtual dynamic shared object",
the kernel system call handler
[anon:<name>]            = an anonymous mapping that has been
named by userspace

or if empty, the mapping is anonymous.

The /proc/PID/task/TID/maps is a view of the virtual memory from the viewpoint
of the individual tasks of a process. In this file you will see a mapping marked
as [stack] if that task sees it as a stack. This is a key difference from the
content of /proc/PID/maps, where you will see all mappings that are being used
as stack by all of those tasks. Hence, for the example above, the task-level
map, i.e. /proc/PID/task/TID/maps for thread 1001 will look like this:

08048000-08049000 r-xp 00000000 03:00 8312       /opt/test
08049000-0804a000 rw-p 00001000 03:00 8312       /opt/test
0804a000-0806b000 rw-p 00000000 00:00 0          [heap]
a7cb1000-a7cb2000 ---p 00000000 00:00 0
a7cb2000-a7eb2000 rw-p 00000000 00:00 0
a7eb2000-a7eb3000 ---p 00000000 00:00 0
a7eb3000-a7ed5000 rw-p 00000000 00:00 0          [stack]
a7ed5000-a8008000 r-xp 00000000 03:00 4222       /lib/libc.so.6
a8008000-a800a000 r--p 00133000 03:00 4222       /lib/libc.so.6
a800a000-a800b000 rw-p 00135000 03:00 4222       /lib/libc.so.6
a800b000-a800e000 rw-p 00000000 00:00 0
a800e000-a8022000 r-xp 00000000 03:00 14462      /lib/libpthread.so.0
a8022000-a8023000 r--p 00013000 03:00 14462      /lib/libpthread.so.0
a8023000-a8024000 rw-p 00014000 03:00 14462      /lib/libpthread.so.0
a8024000-a8027000 rw-p 00000000 00:00 0
a8027000-a8043000 r-xp 00000000 03:00 8317       /lib/ld-linux.so.2
a8043000-a8044000 r--p 0001b000 03:00 8317       /lib/ld-linux.so.2
a8044000-a8045000 rw-p 0001c000 03:00 8317       /lib/ld-linux.so.2
aff35000-aff4a000 rw-p 00000000 00:00 0
ffffe000-fffff000 r-xp 00000000 00:00 0          [vdso]

The /proc/PID/smaps is an extension based on maps, showing the memory
consumption for each of the process's mappings. For each of mappings there
is a series of lines such as the following:

08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
Size:               1084 kB
Rss:                 892 kB
Pss:                 374 kB
Shared_Clean:        892 kB
Shared_Dirty:          0 kB
Private_Clean:         0 kB
Private_Dirty:         0 kB
Referenced:          892 kB
Anonymous:             0 kB
Swap:                  0 kB
KernelPageSize:        4 kB
MMUPageSize:           4 kB
Locked:              374 kB
VmFlags: rd ex mr mw me de
Name:           name from userspace

the first of these lines shows the same information as is displayed for the
mapping in /proc/PID/maps.  The remaining lines show the size of the mapping
(size), the amount of the mapping that is currently resident in RAM (RSS), the
process' proportional share of this mapping (PSS), the number of clean and
dirty private pages in the mapping.  Note that even a page which is part of a
MAP_SHARED mapping, but has only a single pte mapped, i.e.  is currently used
by only one process, is accounted as private and not as shared.  "Referenced"
indicates the amount of memory currently marked as referenced or accessed.
"Anonymous" shows the amount of memory that does not belong to any file.  Even
a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
and a page is modified, the file page is replaced by a private anonymous copy.
"Swap" shows how much would-be-anonymous memory is also used, but out on
swap.

"VmFlags" field deserves a separate description. This member represents the kernel
flags associated with the particular virtual memory area in two letter encoded
manner. The codes are the following:
rd  - readable
wr  - writeable
ex  - executable
sh  - shared
mr  - may read
mw  - may write
me  - may execute
ms  - may share
gd  - stack segment growns down
pf  - pure PFN range
dw  - disabled write to the mapped file
lo  - pages are locked in memory
io  - memory mapped I/O area
sr  - sequential read advise provided
rr  - random read advise provided
dc  - do not copy area on fork
de  - do not expand area on remapping
ac  - area is accountable
nr  - swap space is not reserved for the area
ht  - area uses huge tlb pages
nl  - non-linear mapping
ar  - architecture specific flag
dd  - do not include area into core dump
mm  - mixed map area
hg  - huge page advise flag
nh  - no-huge page advise flag
mg  - mergable advise flag

Note that there is no guarantee that every flag and associated mnemonic will
be present in all further kernel releases. Things get changed, the flags may
be vanished or the reverse -- new added.

The "Name" field will only be present on a mapping that has been named by
userspace, and will show the name passed in by userspace.

This file is only present if the CONFIG_MMU kernel configuration option is
enabled.

The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
bits on both physical and virtual pages associated with a process.
To clear the bits for all the pages associated with the process
> echo 1 > /proc/PID/clear_refs

To clear the bits for the anonymous pages associated with the process
> echo 2 > /proc/PID/clear_refs

To clear the bits for the file mapped pages associated with the process
> echo 3 > /proc/PID/clear_refs
Any other value written to /proc/PID/clear_refs will have no effect.

To reset the peak resident set size ("high water mark") to the process's
current value:
> echo 5 > /proc/PID/clear_refs

The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
using /proc/kpageflags and number of times a page is mapped using
/proc/kpagecount. For detailed explanation, see Documentation/vm/pagemap.txt.

1.2 Kernel data
---------------

Similar to  the  process entries, the kernel data files give information about
the running kernel. The files used to obtain this information are contained in
/proc and  are  listed  in Table 1-5. Not all of these will be present in your
system. It  depends  on the kernel configuration and the loaded modules, which
files are there, and which are missing.

Table 1-5: Kernel info in /proc
..............................................................................
File        Content
apm         Advanced power management info
buddyinfo   Kernel memory allocator information (see text)	(2.5)
bus         Directory containing bus specific information
cmdline     Kernel command line
cpuinfo     Info about the CPU
devices     Available devices (block and character)
dma         Used DMS channels
filesystems Supported filesystems
driver	     Various drivers grouped here, currently rtc (2.4)
execdomains Execdomains, related to security			(2.4)
fb	     Frame Buffer devices				(2.4)
fs	     File system parameters, currently nfs/exports	(2.4)
ide         Directory containing info about the IDE subsystem
interrupts  Interrupt usage
iomem	     Memory map						(2.4)
ioports     I/O port usage
irq	     Masks for irq to cpu affinity			(2.4)(smp?)
isapnp	     ISA PnP (Plug&Play) Info				(2.4)
kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
kmsg        Kernel messages
ksyms       Kernel symbol table
loadavg     Load average of last 1, 5 & 15 minutes
locks       Kernel locks
meminfo     Memory info
misc        Miscellaneous
modules     List of loaded modules
mounts      Mounted filesystems
net         Networking info (see text)
pagetypeinfo Additional page allocator information (see text)  (2.5)
partitions  Table of partitions known to the system
pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
decoupled by lspci					(2.4)
rtc         Real time clock
scsi        SCSI info (see text)
slabinfo    Slab pool info
softirqs    softirq usage
stat        Overall statistics
swaps       Swap space utilization
sys         See chapter 2
sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
tty	     Info of tty drivers
uptime      System uptime
version     Kernel version
video	     bttv info of video resources			(2.4)
vmallocinfo Show vmalloced areas
..............................................................................

You can,  for  example,  check  which interrupts are currently in use and what
they are used for by looking in the file /proc/interrupts:

> cat /proc/interrupts
CPU0
0:    8728810          XT-PIC  timer
1:        895          XT-PIC  keyboard
2:          0          XT-PIC  cascade
3:     531695          XT-PIC  aha152x
4:    2014133          XT-PIC  serial
5:      44401          XT-PIC  pcnet_cs
8:          2          XT-PIC  rtc
11:          8          XT-PIC  i82365
12:     182918          XT-PIC  PS/2 Mouse
13:          1          XT-PIC  fpu
14:    1232265          XT-PIC  ide0
15:          7          XT-PIC  ide1
NMI:          0

In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
output of a SMP machine):

> cat /proc/interrupts

CPU0       CPU1
0:    1243498    1214548    IO-APIC-edge  timer
1:       8949       8958    IO-APIC-edge  keyboard
2:          0          0          XT-PIC  cascade
5:      11286      10161    IO-APIC-edge  soundblaster
8:          1          0    IO-APIC-edge  rtc
9:      27422      27407    IO-APIC-edge  3c503
12:     113645     113873    IO-APIC-edge  PS/2 Mouse
13:          0          0          XT-PIC  fpu
14:      22491      24012    IO-APIC-edge  ide0
15:       2183       2415    IO-APIC-edge  ide1
17:      30564      30414   IO-APIC-level  eth0
18:        177        164   IO-APIC-level  bttv
NMI:    2457961    2457959
LOC:    2457882    2457881
ERR:       2155

NMI is incremented in this case because every timer interrupt generates a NMI
(Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.

LOC is the local interrupt counter of the internal APIC of every CPU.

ERR is incremented in the case of errors in the IO-APIC bus (the bus that
connects the CPUs in a SMP system. This means that an error has been detected,
the IO-APIC automatically retry the transmission, so it should not be a big
problem, but you should read the SMP-FAQ.

In 2.6.2* /proc/interrupts was expanded again.  This time the goal was for
/proc/interrupts to display every IRQ vector in use by the system, not
just those considered 'most important'.  The new vectors are:

THR -- interrupt raised when a machine check threshold counter
(typically counting ECC corrected errors of memory or cache) exceeds
a configurable threshold.  Only available on some systems.

TRM -- a thermal event interrupt occurs when a temperature threshold
has been exceeded for the CPU.  This interrupt may also be generated
when the temperature drops back to normal.

SPU -- a spurious interrupt is some interrupt that was raised then lowered
by some IO device before it could be fully processed by the APIC.  Hence
the APIC sees the interrupt but does not know what device it came from.
For this case the APIC will generate the interrupt with a IRQ vector
of 0xff. This might also be generated by chipset bugs.

RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
sent from one CPU to another per the needs of the OS.  Typically,
their statistics are used by kernel developers and interested users to
determine the occurrence of interrupts of the given type.

The above IRQ vectors are displayed only when relevant.  For example,
the threshold vector does not exist on x86_64 platforms.  Others are
suppressed when the system is a uniprocessor.  As of this writing, only
i386 and x86_64 platforms support the new IRQ vector displays.

Of some interest is the introduction of the /proc/irq directory to 2.4.
It could be used to set IRQ to CPU affinity, this means that you can "hook" an
IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
prof_cpu_mask.

For example
> ls /proc/irq/
0  10  12  14  16  18  2  4  6  8  prof_cpu_mask
1  11  13  15  17  19  3  5  7  9  default_smp_affinity
> ls /proc/irq/0/
smp_affinity

smp_affinity is a bitmask, in which you can specify which CPUs can handle the
IRQ, you can set it by doing:

> echo 1 > /proc/irq/10/smp_affinity

This means that only the first CPU will handle the IRQ, but you can also echo
5 which means that only the first and fourth CPU can handle the IRQ.

The contents of each smp_affinity file is the same by default:

> cat /proc/irq/0/smp_affinity
ffffffff

There is an alternate interface, smp_affinity_list which allows specifying
a cpu range instead of a bitmask:

> cat /proc/irq/0/smp_affinity_list
1024-1031

The default_smp_affinity mask applies to all non-active IRQs, which are the
IRQs which have not yet been allocated/activated, and hence which lack a
/proc/irq/[0-9]* directory.

The node file on an SMP system shows the node to which the device using the IRQ
reports itself as being attached. This hardware locality information does not
include information about any possible driver locality preference.

prof_cpu_mask specifies which CPUs are to be profiled by the system wide
profiler. Default value is ffffffff (all cpus if there are only 32 of them).

The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
between all the CPUs which are allowed to handle it. As usual the kernel has
more info than you and does a better job than you, so the defaults are the
best choice for almost everyone.  [Note this applies only to those IO-APIC's
that support "Round Robin" interrupt distribution.]

There are  three  more  important subdirectories in /proc: net, scsi, and sys.
The general  rule  is  that  the  contents,  or  even  the  existence of these
directories, depend  on your kernel configuration. If SCSI is not enabled, the
directory scsi  may  not  exist. The same is true with the net, which is there
only when networking support is present in the running kernel.

The slabinfo  file  gives  information  about  memory usage at the slab level.
Linux uses  slab  pools for memory management above page level in version 2.2.
Commonly used  objects  have  their  own  slab  pool (such as network buffers,
directory cache, and so on).

..............................................................................

> cat /proc/buddyinfo

Node 0, zone      DMA      0      4      5      4      4      3 ...
Node 0, zone   Normal      1      0      0      1    101      8 ...
Node 0, zone  HighMem      2      0      0      1      1      0 ...

External fragmentation is a problem under some workloads, and buddyinfo is a
useful tool for helping diagnose these problems.  Buddyinfo will give you a
clue as to how big an area you can safely allocate, or why a previous
allocation failed.

Each column represents the number of pages of a certain order which are
available.  In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...

More information relevant to external fragmentation can be found in
pagetypeinfo.

> cat /proc/pagetypeinfo
Page block order: 9
Pages per block:  512

Free pages count per migrate type at order       0      1      2      3      4      5      6      7      8      9     10
Node    0, zone      DMA, type    Unmovable      0      0      0      1      1      1      1      1      1      1      0
Node    0, zone      DMA, type  Reclaimable      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone      DMA, type      Movable      1      1      2      1      2      1      1      0      1      0      2
Node    0, zone      DMA, type      Reserve      0      0      0      0      0      0      0      0      0      1      0
Node    0, zone      DMA, type      Isolate      0      0      0      0      0      0      0      0      0      0      0
Node    0, zone    DMA32, type    Unmovable    103     54     77      1      1      1     11      8      7      1      9
Node    0, zone    DMA32, type  Reclaimable      0      0      2      1      0      0      0      0      1      0      0
Node    0, zone    DMA32, type      Movable    169    152    113     91     77     54     39     13      6      1    452
Node    0, zone    DMA32, type      Reserve      1      2      2      2      2      0      1      1      1      1      0
Node    0, zone    DMA32, type      Isolate      0      0      0      0      0      0      0      0      0      0      0

Number of blocks type     Unmovable  Reclaimable      Movable      Reserve      Isolate
Node 0, zone      DMA            2            0            5            1            0
Node 0, zone    DMA32           41            6          967            2            0

Fragmentation avoidance in the kernel works by grouping pages of different
migrate types into the same contiguous regions of memory called page blocks.
A page block is typically the size of the default hugepage size e.g. 2MB on
X86-64. By keeping pages grouped based on their ability to move, the kernel
can reclaim pages within a page block to satisfy a high-order allocation.

The pagetypinfo begins with information on the size of a page block. It
then gives the same type of information as buddyinfo except broken down
by migrate-type and finishes with details on how many page blocks of each
type exist.

If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
from libhugetlbfs http://sourceforge.net/projects/libhugetlbfs/), one can
make an estimate of the likely number of huge pages that can be allocated
at a given point in time. All the "Movable" blocks should be allocatable
unless memory has been mlock()'d. Some of the Reclaimable blocks should
also be allocatable although a lot of filesystem metadata may have to be
reclaimed to achieve this.

..............................................................................

meminfo:

Provides information about distribution and utilization of memory.  This
varies by architecture and compile options.  The following is from a
16GB PIII, which has highmem enabled.  You may not have all of these fields.

> cat /proc/meminfo

The "Locked" indicates whether the mapping is locked in memory or not.

MemTotal:     16344972 kB
MemFree:      13634064 kB
Buffers:          3656 kB
Cached:        1195708 kB
SwapCached:          0 kB
Active:         891636 kB
Inactive:      1077224 kB
HighTotal:    15597528 kB
HighFree:     13629632 kB
LowTotal:       747444 kB
LowFree:          4432 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:             968 kB
Writeback:           0 kB
AnonPages:      861800 kB
Mapped:         280372 kB
Slab:           284364 kB
SReclaimable:   159856 kB
SUnreclaim:     124508 kB
PageTables:      24448 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
WritebackTmp:        0 kB
CommitLimit:   7669796 kB
Committed_AS:   100056 kB
VmallocTotal:   112216 kB
VmallocUsed:       428 kB
VmallocChunk:   111088 kB
AnonHugePages:   49152 kB

MemTotal: Total usable ram (i.e. physical ram minus a few reserved
bits and the kernel binary code)
MemFree: The sum of LowFree+HighFree
Buffers: Relatively temporary storage for raw disk blocks
shouldn't get tremendously large (20MB or so)
Cached: in-memory cache for files read from the disk (the
pagecache).  Doesn't include SwapCached
SwapCached: Memory that once was swapped out, is swapped back in but
still also is in the swapfile (if memory is needed it
doesn't need to be swapped out AGAIN because it is already
in the swapfile. This saves I/O)
Active: Memory that has been used more recently and usually not
reclaimed unless absolutely necessary.
Inactive: Memory which has been less recently used.  It is more
eligible to be reclaimed for other purposes
HighTotal:
HighFree: Highmem is all memory above ~860MB of physical memory
Highmem areas are for use by userspace programs, or
for the pagecache.  The kernel must use tricks to access
this memory, making it slower to access than lowmem.
LowTotal:
LowFree: Lowmem is memory which can be used for everything that
highmem can be used for, but it is also available for the
kernel's use for its own data structures.  Among many
other things, it is where everything from the Slab is
allocated.  Bad things happen when you're out of lowmem.
SwapTotal: total amount of swap space available
SwapFree: Memory which has been evicted from RAM, and is temporarily
on the disk
Dirty: Memory which is waiting to get written back to the disk
Writeback: Memory which is actively being written back to the disk
AnonPages: Non-file backed pages mapped into userspace page tables
AnonHugePages: Non-file backed huge pages mapped into userspace page tables
Mapped: files which have been mmaped, such as libraries
Slab: in-kernel data structures cache
SReclaimable: Part of Slab, that might be reclaimed, such as caches
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
PageTables: amount of memory dedicated to the lowest level of page
tables.
NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
storage
Bounce: Memory used for block device "bounce buffers"
WritebackTmp: Memory used by FUSE for temporary writeback buffers
CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
this is the total amount of  memory currently available to
be allocated on the system. This limit is only adhered to
if strict overcommit accounting is enabled (mode 2 in
'vm.overcommit_memory').
The CommitLimit is calculated with the following formula:
CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
For example, on a system with 1G of physical RAM and 7G
of swap with a `vm.overcommit_ratio` of 30 it would
yield a CommitLimit of 7.3G.
For more details, see the memory overcommit documentation
in vm/overcommit-accounting.
Committed_AS: The amount of memory presently allocated on the system.
The committed memory is a sum of all of the memory which
has been allocated by processes, even if it has not been
"used" by them as of yet. A process which malloc()'s 1G
of memory, but only touches 300M of it will only show up
as using 300M of memory even if it has the address space
allocated for the entire 1G. This 1G is memory which has
been "committed" to by the VM and can be used at any time
by the allocating application. With strict overcommit
enabled on the system (mode 2 in 'vm.overcommit_memory'),
allocations which would exceed the CommitLimit (detailed
above) will not be permitted. This is useful if one needs
to guarantee that processes will not fail due to lack of
memory once that memory has been successfully allocated.
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contiguous block of vmalloc area which is free

..............................................................................

vmallocinfo:

Provides information about vmalloced/vmaped areas. One line per area,
containing the virtual address range of the area, size in bytes,
caller information of the creator, and optional information depending
on the kind of area :

pages=nr    number of pages
phys=addr   if a physical address was specified
ioremap     I/O mapping (ioremap() and friends)
vmalloc     vmalloc() area
vmap        vmap()ed pages
user        VM_USERMAP area
vpages      buffer for pages pointers was vmalloced (huge area)
N<node>=nr  (Only on NUMA kernels)
Number of pages allocated on memory node <node>

> cat /proc/vmallocinfo
0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
/0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
/0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
0xffffc20000302000-0xffffc20000304000    8192 acpi_tb_verify_table+0x21/0x4f...
phys=7fee8000 ioremap
0xffffc20000304000-0xffffc20000307000   12288 acpi_tb_verify_table+0x21/0x4f...
phys=7fee7000 ioremap
0xffffc2000031d000-0xffffc2000031f000    8192 init_vdso_vars+0x112/0x210
0xffffc2000031f000-0xffffc2000032b000   49152 cramfs_uncompress_init+0x2e ...
/0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
0xffffc2000033a000-0xffffc2000033d000   12288 sys_swapon+0x640/0xac0      ...
pages=2 vmalloc N1=2
0xffffc20000347000-0xffffc2000034c000   20480 xt_alloc_table_info+0xfe ...
/0x130 [x_tables] pages=4 vmalloc N0=4
0xffffffffa0000000-0xffffffffa000f000   61440 sys_init_module+0xc27/0x1d00 ...
pages=14 vmalloc N2=14
0xffffffffa000f000-0xffffffffa0014000   20480 sys_init_module+0xc27/0x1d00 ...
pages=4 vmalloc N1=4
0xffffffffa0014000-0xffffffffa0017000   12288 sys_init_module+0xc27/0x1d00 ...
pages=2 vmalloc N1=2
0xffffffffa0017000-0xffffffffa0022000   45056 sys_init_module+0xc27/0x1d00 ...
pages=10 vmalloc N0=10

..............................................................................

softirqs:

Provides counts of softirq handlers serviced since boot time, for each cpu.

> cat /proc/softirqs
CPU0       CPU1       CPU2       CPU3
HI:          0          0          0          0
TIMER:      27166      27120      27097      27034
NET_TX:          0          0          0         17
NET_RX:         42          0          0         39
BLOCK:          0          0        107       1121
TASKLET:          0          0          0        290
SCHED:      27035      26983      26971      26746
HRTIMER:          0          0          0          0
RCU:       1678       1769       2178       2250

1.3 IDE devices in /proc/ide
----------------------------

The subdirectory /proc/ide contains information about all IDE devices of which
the kernel  is  aware.  There is one subdirectory for each IDE controller, the
file drivers  and a link for each IDE device, pointing to the device directory
in the controller specific subtree.

The file  drivers  contains general information about the drivers used for the
IDE devices:

> cat /proc/ide/drivers
ide-cdrom version 4.53
ide-disk version 1.08

More detailed  information  can  be  found  in  the  controller  specific
subdirectories. These  are  named  ide0,  ide1  and  so  on.  Each  of  these
directories contains the files shown in table 1-6.

Table 1-6: IDE controller info in  /proc/ide/ide?
..............................................................................
File    Content
channel IDE channel (0 or 1)
config  Configuration (only for PCI/IDE bridge)
mate    Mate name
model   Type/Chipset of IDE controller
..............................................................................

Each device  connected  to  a  controller  has  a separate subdirectory in the
controllers directory.  The  files  listed in table 1-7 are contained in these
directories.

Table 1-7: IDE device information
..............................................................................
File             Content
cache            The cache
capacity         Capacity of the medium (in 512Byte blocks)
driver           driver and version
geometry         physical and logical geometry
identify         device identify block
media            media type
model            device identifier
settings         device setup
smart_thresholds IDE disk management thresholds
smart_values     IDE disk management values
..............................................................................

The most  interesting  file is settings. This file contains a nice overview of
the drive parameters:

# cat /proc/ide/ide0/hda/settings
name                    value           min             max             mode
----                    -----           ---             ---             ----
bios_cyl                526             0               65535           rw
bios_head               255             0               255             rw
bios_sect               63              0               63              rw
breada_readahead        4               0               127             rw
bswap                   0               0               1               r
file_readahead          72              0               2097151         rw
io_32bit                0               0               3               rw
keepsettings            0               0               1               rw
max_kb_per_request      122             1               127             rw
multcount               0               0               8               rw
nice1                   1               0               1               rw
nowerr                  0               0               1               rw
pio_mode                write-only      0               255             w
slow                    0               0               1               rw
unmaskirq               0               0               1               rw
using_dma               0               0               1               rw

1.4 Networking info in /proc/net
--------------------------------

The subdirectory  /proc/net  follows  the  usual  pattern. Table 1-8 shows the
additional values  you  get  for  IP  version 6 if you configure the kernel to
support this. Table 1-9 lists the files and their meaning.

Table 1-8: IPv6 info in /proc/net
..............................................................................
File       Content
udp6       UDP sockets (IPv6)
tcp6       TCP sockets (IPv6)
raw6       Raw device statistics (IPv6)
igmp6      IP multicast addresses, which this host joined (IPv6)
if_inet6   List of IPv6 interface addresses
ipv6_route Kernel routing table for IPv6
rt6_stats  Global IPv6 routing tables statistics
sockstat6  Socket statistics (IPv6)
snmp6      Snmp data (IPv6)
..............................................................................

Table 1-9: Network info in /proc/net
..............................................................................
File          Content
arp           Kernel  ARP table
dev           network devices with statistics
dev_mcast     the Layer2 multicast groups a device is listening too
(interface index, label, number of references, number of bound
addresses).
dev_stat      network device status
ip_fwchains   Firewall chain linkage
ip_fwnames    Firewall chain names
ip_masq       Directory containing the masquerading tables
ip_masquerade Major masquerading table
netstat       Network statistics
raw           raw device statistics
route         Kernel routing table
rpc           Directory containing rpc info
rt_cache      Routing cache
snmp          SNMP data
sockstat      Socket statistics
tcp           TCP  sockets
udp           UDP sockets
unix          UNIX domain sockets
wireless      Wireless interface data (Wavelan etc)
igmp          IP multicast addresses, which this host joined
psched        Global packet scheduler parameters.
netlink       List of PF_NETLINK sockets
ip_mr_vifs    List of multicast virtual interfaces
ip_mr_cache   List of multicast routing cache
..............................................................................

You can  use  this  information  to see which network devices are available in
your system and how much traffic was routed over those devices:

> cat /proc/net/dev
Inter-|Receive                                                   |[...
face |bytes    packets errs drop fifo frame compressed multicast|[...
lo:  908188   5596     0    0    0     0          0         0 [...
ppp0:15475140  20721   410    0    0   410          0         0 [...
eth0:  614530   7085     0    0    0     0          0         1 [...

...] Transmit
...] bytes    packets errs drop fifo colls carrier compressed
...]  908188     5596    0    0    0     0       0          0
...] 1375103    17405    0    0    0     0       0          0
...] 1703981     5535    0    0    0     3       0          0

In addition, each Channel Bond interface has its own directory.  For
example, the bond0 device will have a directory called /proc/net/bond0/.
It will contain information that is specific to that bond, such as the
current slaves of the bond, the link status of the slaves, and how
many times the slaves link has failed.

1.5 SCSI info
-------------

If you  have  a  SCSI  host adapter in your system, you'll find a subdirectory
named after  the driver for this adapter in /proc/scsi. You'll also see a list
of all recognized SCSI devices in /proc/scsi:

>cat /proc/scsi/scsi
Attached devices:
Host: scsi0 Channel: 00 Id: 00 Lun: 00
Vendor: IBM      Model: DGHS09U          Rev: 03E0
Type:   Direct-Access                    ANSI SCSI revision: 03
Host: scsi0 Channel: 00 Id: 06 Lun: 00
Vendor: PIONEER  Model: CD-ROM DR-U06S   Rev: 1.04
Type:   CD-ROM                           ANSI SCSI revision: 02

The directory  named  after  the driver has one file for each adapter found in
the system.  These  files  contain information about the controller, including
the used  IRQ  and  the  IO  address range. The amount of information shown is
dependent on  the adapter you use. The example shows the output for an Adaptec
AHA-2940 SCSI adapter:

> cat /proc/scsi/aic7xxx/0

Adaptec AIC7xxx driver version: 5.1.19/3.2.4
Compile Options:
TCQ Enabled By Default : Disabled
AIC7XXX_PROC_STATS     : Disabled
AIC7XXX_RESET_DELAY    : 5
Adapter Configuration:
SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
Ultra Wide Controller
PCI MMAPed I/O Base: 0xeb001000
Adapter SEEPROM Config: SEEPROM found and used.
Adaptec SCSI BIOS: Enabled
IRQ: 10
SCBs: Active 0, Max Active 2,
Allocated 15, HW 16, Page 255
Interrupts: 160328
BIOS Control Word: 0x18b6
Adapter Control Word: 0x005b
Extended Translation: Enabled
Disconnect Enable Flags: 0xffff
Ultra Enable Flags: 0x0001
Tag Queue Enable Flags: 0x0000
Ordered Queue Tag Flags: 0x0000
Default Tag Queue Depth: 8
Tagged Queue By Device array for aic7xxx host instance 0:
{255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
Actual queue depth per device for aic7xxx host instance 0:
{1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
Statistics:
(scsi0:0:0:0)
Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
Total transfers 160151 (74577 reads and 85574 writes)
(scsi0:0:6:0)
Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
Total transfers 0 (0 reads and 0 writes)

1.6 Parallel port info in /proc/parport
---------------------------------------

The directory  /proc/parport  contains information about the parallel ports of
your system.  It  has  one  subdirectory  for  each port, named after the port
number (0,1,2,...).

These directories contain the four files shown in Table 1-10.

Table 1-10: Files in /proc/parport
..............................................................................
File      Content
autoprobe Any IEEE-1284 device ID information that has been acquired.
devices   list of the device drivers using that port. A + will appear by the
name of the device currently using the port (it might not appear
against any).
hardware  Parallel port's base address, IRQ line and DMA channel.
irq       IRQ that parport is using for that port. This is in a separate
file to allow you to alter it by writing a new value in (IRQ
number or none).
..............................................................................

1.7 TTY info in /proc/tty
-------------------------

Information about  the  available  and actually used tty's can be found in the
directory /proc/tty.You'll  find  entries  for drivers and line disciplines in
this directory, as shown in Table 1-11.

Table 1-11: Files in /proc/tty
..............................................................................
File          Content
drivers       list of drivers and their usage
ldiscs        registered line disciplines
driver/serial usage statistic and status of single tty lines
..............................................................................

To see  which  tty's  are  currently in use, you can simply look into the file
/proc/tty/drivers:

> cat /proc/tty/drivers
pty_slave            /dev/pts      136   0-255 pty:slave
pty_master           /dev/ptm      128   0-255 pty:master
pty_slave            /dev/ttyp       3   0-255 pty:slave
pty_master           /dev/pty        2   0-255 pty:master
serial               /dev/cua        5   64-67 serial:callout
serial               /dev/ttyS       4   64-67 serial
/dev/tty0            /dev/tty0       4       0 system:vtmaster
/dev/ptmx            /dev/ptmx       5       2 system
/dev/console         /dev/console    5       1 system:console
/dev/tty             /dev/tty        5       0 system:/dev/tty
unknown              /dev/tty        4    1-63 console

1.8 Miscellaneous kernel statistics in /proc/stat
-------------------------------------------------

Various pieces   of  information about  kernel activity  are  available in the
/proc/stat file.  All  of  the numbers reported  in  this file are  aggregates
since the system first booted.  For a quick look, simply cat the file:

> cat /proc/stat
cpu  2255 34 2290 22625563 6290 127 456 0 0
cpu0 1132 34 1441 11311718 3675 127 438 0 0
cpu1 1123 0 849 11313845 2614 0 18 0 0
intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
ctxt 1990473
btime 1062191376
processes 2915
procs_running 1
procs_blocked 0
softirq 183433 0 21755 12 39 1137 231 21459 2263

The very first  "cpu" line aggregates the  numbers in all  of the other "cpuN"
lines.  These numbers identify the amount of time the CPU has spent performing
different kinds of work.  Time units are in USER_HZ (typically hundredths of a
second).  The meanings of the columns are as follows, from left to right:

- user: normal processes executing in user mode
- nice: niced processes executing in user mode
- system: processes executing in kernel mode
- idle: twiddling thumbs
- iowait: waiting for I/O to complete
- irq: servicing interrupts
- softirq: servicing softirqs
- steal: involuntary wait
- guest: running a normal guest
- guest_nice: running a niced guest

The "intr" line gives counts of interrupts  serviced since boot time, for each
of the  possible system interrupts.   The first  column  is the  total of  all
interrupts serviced; each  subsequent column is the  total for that particular
interrupt.

The "ctxt" line gives the total number of context switches across all CPUs.

The "btime" line gives  the time at which the  system booted, in seconds since
the Unix epoch.

The "processes" line gives the number  of processes and threads created, which
includes (but  is not limited  to) those  created by  calls to the  fork() and
clone() system calls.

The "procs_running" line gives the total number of threads that are
running or ready to run (i.e., the total number of runnable threads).

The   "procs_blocked" line gives  the  number of  processes currently blocked,
waiting for I/O to complete.

The "softirq" line gives counts of softirqs serviced since boot time, for each
of the possible system softirqs. The first column is the total of all
softirqs serviced; each subsequent column is the total for that particular
softirq.

1.9 Ext4 file system parameters
------------------------------

Information about mounted ext4 file systems can be found in
/proc/fs/ext4.  Each mounted filesystem will have a directory in
/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
/proc/fs/ext4/dm-0).   The files in each per-device directory are shown
in Table 1-12, below.

Table 1-12: Files in /proc/fs/ext4/<devname>
..............................................................................
File            Content
mb_groups       details of multiblock allocator buddy cache of free blocks
..............................................................................

2.0 /proc/consoles
------------------
Shows registered system console lines.

To see which character device lines are currently used for the system console
/dev/console, you may simply look into the file /proc/consoles:

> cat /proc/consoles
tty0                 -WU (ECp)       4:7
ttyS0                -W- (Ep)        4:64

The columns are:

device               name of the device
operations           R = can do read operations
W = can do write operations
U = can do unblank
flags                E = it is enabled
C = it is preferred console
B = it is primary boot console
p = it is used for printk buffer
b = it is not a TTY but a Braille device
a = it is safe to use when cpu is offline
major:minor          major and minor number of the device separated by a colon

------------------------------------------------------------------------------
Summary
------------------------------------------------------------------------------
The /proc file system serves information about the running system. It not only
allows access to process data but also allows you to request the kernel status
by reading files in the hierarchy.

The directory  structure  of /proc reflects the types of information and makes
it easy, if not obvious, where to look for specific data.
------------------------------------------------------------------------------

------------------------------------------------------------------------------
CHAPTER 2: MODIFYING SYSTEM PARAMETERS
------------------------------------------------------------------------------

------------------------------------------------------------------------------
In This Chapter
------------------------------------------------------------------------------
* Modifying kernel parameters by writing into files found in /proc/sys
* Exploring the files which modify certain parameters
* Review of the /proc/sys file tree
------------------------------------------------------------------------------

A very  interesting part of /proc is the directory /proc/sys. This is not only
a source  of  information,  it also allows you to change parameters within the
kernel. Be  very  careful  when attempting this. You can optimize your system,
but you  can  also  cause  it  to  crash.  Never  alter kernel parameters on a
production system.  Set  up  a  development machine and test to make sure that
everything works  the  way  you want it to. You may have no alternative but to
reboot the machine once an error has been made.

To change  a  value,  simply  echo  the new value into the file. An example is
given below  in the section on the file system data. You need to be root to do
this. You  can  create  your  own  boot script to perform this every time your
system boots.

The files  in /proc/sys can be used to fine tune and monitor miscellaneous and
general things  in  the operation of the Linux kernel. Since some of the files
can inadvertently  disrupt  your  system,  it  is  advisable  to  read  both
documentation and  source  before actually making adjustments. In any case, be
very careful  when  writing  to  any  of these files. The entries in /proc may
change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
review the kernel documentation in the directory /usr/src/linux/Documentation.
This chapter  is  heavily  based  on the documentation included in the pre 2.2
kernels, and became part of it in version 2.2.1 of the Linux kernel.

Please see: Documentation/sysctl/ directory for descriptions of these
entries.

------------------------------------------------------------------------------
Summary
------------------------------------------------------------------------------
Certain aspects  of  kernel  behavior  can be modified at runtime, without the
need to  recompile  the kernel, or even to reboot the system. The files in the
/proc/sys tree  can  not only be read, but also modified. You can use the echo
command to write value into these files, thereby changing the default settings
of the kernel.
------------------------------------------------------------------------------

------------------------------------------------------------------------------
CHAPTER 3: PER-PROCESS PARAMETERS
------------------------------------------------------------------------------

3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
--------------------------------------------------------------------------------

These file can be used to adjust the badness heuristic used to select which
process gets killed in out of memory conditions.

The badness heuristic assigns a value to each candidate task ranging from 0
(never kill) to 1000 (always kill) to determine which process is targeted.  The
units are roughly a proportion along that range of allowed memory the process
may allocate from based on an estimation of its current memory and swap use.
For example, if a task is using all allowed memory, its badness score will be
1000.  If it is using half of its allowed memory, its score will be 500.

There is an additional factor included in the badness score: the current memory
and swap usage is discounted by 3% for root processes.

The amount of "allowed" memory depends on the context in which the oom killer
was called.  If it is due to the memory assigned to the allocating task's cpuset
being exhausted, the allowed memory represents the set of mems assigned to that
cpuset.  If it is due to a mempolicy's node(s) being exhausted, the allowed
memory represents the set of mempolicy nodes.  If it is due to a memory
limit (or swap limit) being reached, the allowed memory is that configured
limit.  Finally, if it is due to the entire system being out of memory, the
allowed memory represents all allocatable resources.

The value of /proc/<pid>/oom_score_adj is added to the badness score before it
is used to determine which task to kill.  Acceptable values range from -1000
(OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX).  This allows userspace to
polarize the preference for oom killing either by always preferring a certain
task or completely disabling it.  The lowest possible value, -1000, is
equivalent to disabling oom killing entirely for that task since it will always
report a badness score of 0.

Consequently, it is very simple for userspace to define the amount of memory to
consider for each task.  Setting a /proc/<pid>/oom_score_adj value of +500, for
example, is roughly equivalent to allowing the remainder of tasks sharing the
same system, cpuset, mempolicy, or memory controller resources to use at least
50% more memory.  A value of -500, on the other hand, would be roughly
equivalent to discounting 50% of the task's allowed memory from being considered
as scoring against the task.

For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
be used to tune the badness score.  Its acceptable values range from -16
(OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
(OOM_DISABLE) to disable oom killing entirely for that task.  Its value is
scaled linearly with /proc/<pid>/oom_score_adj.

The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
requires CAP_SYS_RESOURCE.

Caveat: when a parent task is selected, the oom killer will sacrifice any first
generation children with separate address spaces instead, if possible.  This
avoids servers and important system daemons from being killed and loses the
minimal amount of work.

3.2 /proc/<pid>/oom_score - Display current oom-killer score
-------------------------------------------------------------

This file can be used to check the current score used by the oom-killer is for
any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
process should be killed in an out-of-memory situation.

3.3  /proc/<pid>/io - Display the IO accounting fields
-------------------------------------------------------

This file contains IO statistics for each running process

Example
-------

test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
[1] 3828

test:/tmp # cat /proc/3828/io
rchar: 323934931
wchar: 323929600
syscr: 632687
syscw: 632675
read_bytes: 0
write_bytes: 323932160
cancelled_write_bytes: 0

Description
-----------

rchar
-----

I/O counter: chars read
The number of bytes which this task has caused to be read from storage. This
is simply the sum of bytes which this process passed to read() and pread().
It includes things like tty IO and it is unaffected by whether or not actual
physical disk IO was required (the read might have been satisfied from
pagecache)

wchar
-----

I/O counter: chars written
The number of bytes which this task has caused, or shall cause to be written
to disk. Similar caveats apply here as with rchar.

syscr
-----

I/O counter: read syscalls
Attempt to count the number of read I/O operations, i.e. syscalls like read()
and pread().

syscw
-----

I/O counter: write syscalls
Attempt to count the number of write I/O operations, i.e. syscalls like
write() and pwrite().

read_bytes
----------

I/O counter: bytes read
Attempt to count the number of bytes which this process really did cause to
be fetched from the storage layer. Done at the submit_bio() level, so it is
accurate for block-backed filesystems. <please add status regarding NFS and
CIFS at a later time>

write_bytes
-----------

I/O counter: bytes written
Attempt to count the number of bytes which this process caused to be sent to
the storage layer. This is done at page-dirtying time.

cancelled_write_bytes
---------------------

The big inaccuracy here is truncate. If a process writes 1MB to a file and
then deletes the file, it will in fact perform no writeout. But it will have
been accounted as having caused 1MB of write.
In other words: The number of bytes which this process caused to not happen,
by truncating pagecache. A task can cause "negative" IO too. If this task
truncates some dirty pagecache, some IO which another task has been accounted
for (in its write_bytes) will not be happening. We _could_ just subtract that
from the truncating task's write_bytes, but there is information loss in doing
that.

Note
----

At its current implementation state, this is a bit racy on 32-bit machines: if
process A reads process B's /proc/pid/io while process B is updating one of
those 64-bit counters, process A could see an intermediate result.

More information about this can be found within the taskstats documentation in
Documentation/accounting.

3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
---------------------------------------------------------------
When a process is dumped, all anonymous memory is written to a core file as
long as the size of the core file isn't limited. But sometimes we don't want
to dump some memory segments, for example, huge shared memory. Conversely,
sometimes we want to save file-backed memory segments into a core file, not
only the individual files.

/proc/<pid>/coredump_filter allows you to customize which memory segments
will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
of memory types. If a bit of the bitmask is set, memory segments of the
corresponding memory type are dumped, otherwise they are not dumped.

The following 7 memory types are supported:
- (bit 0) anonymous private memory
- (bit 1) anonymous shared memory
- (bit 2) file-backed private memory
- (bit 3) file-backed shared memory
- (bit 4) ELF header pages in file-backed private memory areas (it is
effective only if the bit 2 is cleared)
- (bit 5) hugetlb private memory
- (bit 6) hugetlb shared memory

Note that MMIO pages such as frame buffer are never dumped and vDSO pages
are always dumped regardless of the bitmask status.

Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
effected by bit 5-6.

Default value of coredump_filter is 0x23; this means all anonymous memory
segments and hugetlb private memory are dumped.

If you don't want to dump all shared memory segments attached to pid 1234,
write 0x21 to the process's proc file.

$ echo 0x21 > /proc/1234/coredump_filter

When a new process is created, the process inherits the bitmask status from its
parent. It is useful to set up coredump_filter before the program runs.
For example:

$ echo 0x7 > /proc/self/coredump_filter
$ ./some_program

3.5	/proc/<pid>/mountinfo - Information about mounts
--------------------------------------------------------

This file contains lines of the form:

36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
(1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

(1) mount ID:  unique identifier of the mount (may be reused after umount)
(2) parent ID:  ID of parent (or of self for the top of the mount tree)
(3) major:minor:  value of st_dev for files on filesystem
(4) root:  root of the mount within the filesystem
(5) mount point:  mount point relative to the process's root
(6) mount options:  per mount options
(7) optional fields:  zero or more fields of the form "tag[:value]"
(8) separator:  marks the end of the optional fields
(9) filesystem type:  name of filesystem of the form "type[.subtype]"
(10) mount source:  filesystem specific information or "none"
(11) super options:  per super block options

Parsers should ignore all unrecognised optional fields.  Currently the
possible optional fields are:

shared:X  mount is shared in peer group X
master:X  mount is slave to peer group X
propagate_from:X  mount is slave and receives propagation from peer group X (*)
unbindable  mount is unbindable

(*) X is the closest dominant peer group under the process's root.  If
X is the immediate master of the mount, or if there's no dominant peer
group under the same root, then only the "master:X" field is present
and not the "propagate_from:X" field.

For more information on mount propagation see:

Documentation/filesystems/sharedsubtree.txt

3.6	/proc/<pid>/comm  & /proc/<pid>/task/<tid>/comm
--------------------------------------------------------
These files provide a method to access a tasks comm value. It also allows for
a task to set its own or one of its thread siblings comm value. The comm value
is limited in size compared to the cmdline value, so writing anything longer
then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
comm value.

3.7	/proc/<pid>/task/<tid>/children - Information about task children
-------------------------------------------------------------------------
This file provides a fast way to retrieve first level children pids
of a task pointed by <pid>/<tid> pair. The format is a space separated
stream of pids.

Note the "first level" here -- if a child has own children they will
not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
to obtain the descendants.

Since this interface is intended to be fast and cheap it doesn't
guarantee to provide precise results and some children might be
skipped, especially if they've exited right after we printed their
pids, so one need to either stop or freeze processes being inspected
if precise results are needed.

3.7	/proc/<pid>/fdinfo/<fd> - Information about opened file
---------------------------------------------------------------
This file provides information associated with an opened file. The regular
files have at least two fields -- 'pos' and 'flags'. The 'pos' represents
the current offset of the opened file in decimal form [see lseek(2) for
details] and 'flags' denotes the octal O_xxx mask the file has been
created with [see open(2) for details].

A typical output is

pos:	0
flags:	0100002

The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
pair provide additional information particular to the objects they represent.

Eventfd files
~~~~~~~~~~~~~
pos:	0
flags:	04002
eventfd-count:	5a

where 'eventfd-count' is hex value of a counter.

Signalfd files
~~~~~~~~~~~~~~
pos:	0
flags:	04002
sigmask:	0000000000000200

where 'sigmask' is hex value of the signal mask associated
with a file.

Epoll files
~~~~~~~~~~~
pos:	0
flags:	02
tfd:        5 events:       1d data: ffffffffffffffff

where 'tfd' is a target file descriptor number in decimal form,
'events' is events mask being watched and the 'data' is data
associated with a target [see epoll(7) for more details].

Fsnotify files
~~~~~~~~~~~~~~
For inotify files the format is the following

pos:	0
flags:	02000000
inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d

where 'wd' is a watch descriptor in decimal form, ie a target file
descriptor number, 'ino' and 'sdev' are inode and device where the
target file resides and the 'mask' is the mask of events, all in hex
form [see inotify(7) for more details].

If the kernel was built with exportfs support, the path to the target
file is encoded as a file handle.  The file handle is provided by three
fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
format.

If the kernel is built without exportfs support the file handle won't be
printed out.

If there is no inotify mark attached yet the 'inotify' line will be omitted.

For fanotify files the format is

pos:	0
flags:	02
fanotify flags:10 event-flags:0
fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4

where fanotify 'flags' and 'event-flags' are values used in fanotify_init
call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
flags associated with mark which are tracked separately from events
mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
mask and 'ignored_mask' is the mask of events which are to be ignored.
All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
does provide information about flags and mask used in fanotify_mark
call [see fsnotify manpage for details].

While the first three lines are mandatory and always printed, the rest is
optional and may be omitted if no marks created yet.

------------------------------------------------------------------------------
Configuring procfs
------------------------------------------------------------------------------

4.1	Mount options
---------------------

The following mount options are supported:

hidepid=	Set /proc/<pid>/ access mode.
gid=		Set the group authorized to learn processes information.

hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
(default).

hidepid=1 means users may not access any /proc/<pid>/ directories but their
own.  Sensitive files like cmdline, sched*, status are now protected against
other users.  This makes it impossible to learn whether any user runs
specific program (given the program doesn't reveal itself by its behaviour).
As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
poorly written programs passing sensitive information via program arguments are
now protected against local eavesdroppers.

hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
users.  It doesn't mean that it hides a fact whether a process with a specific
pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
but it hides process' uid and gid, which may be learned by stat()'ing
/proc/<pid>/ otherwise.  It greatly complicates an intruder's task of gathering
information about running processes, whether some daemon runs with elevated
privileges, whether other user runs some sensitive program, whether other users
run any program at all, etc.

gid= defines a group authorized to learn processes information otherwise
prohibited by hidepid=.  If you use some daemon like identd which needs to learn
information about processes information, just add identd to this group.

上面这篇文件时kernel/linux-3.10.y/Documentation/filesystems/proc.txt的原文，下面是翻译。注意翻译省去了一些个人认为不大需要的东西。

0. 目录

1 收集系统信息

1.1 进程子目录

1.2 内核数据

1.3 ide device in /proc/ide

1.4 网络信息  in /proc/net

1.5 SCSI info

1.6 并行串口(Parallel port)信息 in /proc/parport

1.7 TTY info in /proc/tty

1.8 内核统计 in /proc/stat

1.9 Ext4文件系统参数

2 改变系统参数

3 每一个进程参数

3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_socre_adj 调整oom-killer分数

3.2 /proc/<pid>/oom_score 显示现在的oom-killer分数

3.3 /proc/<pid>/io  display the IO accounting fields

3.4 /proc/<pid>/coredump_filter core dump filtering setttings

3.5 /proc/<pid>/mountinfo 挂载信息

3.6 /proc/<pid>comm & /proc/<pid>/task/<tid>/comm

3.7 /proc/<pid>/task/<tid>/children  task children信息

3.8 /proc/<pid>/fdinfo/<fd> 打开文件信息

4 Configuring procfs 安装proc文件系统

4.1 挂载选项

1. 收集系统信息

这章我们将介绍proc这个文件系统提供的信息、架构、以及关于内核和进程的信息。

proc文件系统呈现了kernel的数据结构。同样它可以获取系统信息和改变内核在运行时的参数

1.1 进程子目录

进程信息都在proc/<pid>目录下

Table 1-1: Process specific entries in /proc
..............................................................................
File Content
clear_refs Clears page referenced bits shown in smaps output
cmdline Command line arguments 启动命令参数
cpu Current and last cpu in which it was executed (2.4)(smp)
cwd Link to the current working directory 当前工作目录
environ Values of environment variables 环境变量
exe Link to the executable of this process
fd Directory, which contains all file descriptors 各个fd的软链接
maps Memory maps to executables and library files (2.4)
mem Memory held by this process
root Link to the root directory of this process 进程根目录
stat Process status 进程信息
statm Process memory status information 存储信息
status Process status in human readable form 进程信息
wchan If CONFIG_KALLSYMS is set, a pre-decoded wchan
pagemap Page table
stack Report full stack trace, enable via CONFIG_STACKTRACE
smaps a extension based on maps, showing the memory consumption of
each mapping and flags associated with it
..............................................................................

举个例子：

>cat /proc/self/status
Name:   cat
State:  R (running)
Tgid:   5452
Pid:    5452
PPid:   743
TracerPid:      0						(2.4)
Uid:    501     501     501     501
Gid:    100     100     100     100
FDSize: 256
Groups: 100 14 16
VmPeak:     5004 kB
VmSize:     5004 kB
VmLck:         0 kB
VmHWM:       476 kB
VmRSS:       476 kB
VmData:      156 kB
VmStk:        88 kB
VmExe:        68 kB
VmLib:      1412 kB
VmPTE:        20 kb
VmSwap:        0 kB
Threads:        1
SigQ:   0/28578
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 00000000fffffeff
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: ffffffffffffffff
Seccomp:        0
voluntary_ctxt_switches:        0
nonvoluntary_ctxt_switches:     1

上面的信息可以同样适用ps命令得到。事实上，ps命令就是用了proc文件系统来获取信息。如果你要获取更多信息就要cat proc/<pid>/status

我们来看下上面各个数据的意义

Table 1-2: Contents of the status files (as of 2.6.30-rc7)
..............................................................................
Field                       Content
Name                        filename of the executable //文件名
State                       state (R is running, S is sleeping, D is sleeping //状态 R S D Z等
in an uninterruptible wait, Z is zombie,
T is traced or stopped)
Tgid                        thread group ID 线程租
Pid                         process id 进程id
PPid                        process id of the parent process 父进程
TracerPid                   PID of process tracing this process (0 if not) 跟踪这个进程的pid
Uid                         Real, effective, saved set, and  file system UIDs
Gid                         Real, effective, saved set, and  file system GIDs
FDSize                      number of file descriptor slots currently allocated 已经分配的fd数量
Groups                      supplementary group list 属于哪些租
VmPeak                      peak virtual memory size
VmSize                      total program size
VmLck                       locked memory size
VmHWM                       peak resident set size ("high water mark")
VmRSS                       size of memory portions
VmData                      size of data, stack, and text segments
VmStk                       size of data, stack, and text segments
VmExe                       size of text segment
VmLib                       size of shared library code
VmPTE                       size of page table entries
VmSwap                      size of swap usage (the number of referred swapents)
Threads                     number of threads 线程数量
SigQ                        number of signals queued/max. number for queue 队列中的信号数量/最大信号数量
SigPnd                      bitmap of pending signals for the thread 暂停的信号bit位
ShdPnd                      bitmap of shared pending signals for the process
SigBlk                      bitmap of blocked signals 阻塞的信号bit位
SigIgn                      bitmap of ignored signals 忽略的信号bit位
SigCgt                      bitmap of catched signals 捕获到的信号bit位
CapInh                      bitmap of inheritable capabilities
CapPrm                      bitmap of permitted capabilities
CapEff                      bitmap of effective capabilities
CapBnd                      bitmap of capabilities bounding set
Seccomp                     seccomp mode, like prctl(PR_GET_SECCOMP, ...)
Cpus_allowed                mask of CPUs on which this process may run
Cpus_allowed_list           Same as previous, but in "list format"
Mems_allowed                mask of memory nodes allowed to this process
Mems_allowed_list           Same as previous, but in "list format"
voluntary_ctxt_switches     number of voluntary context switches
nonvoluntary_ctxt_switches  number of non voluntary context switches
..............................................................................

statm文件关于进程更详细的存储使用情况

Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
..............................................................................
Field    Content
size     total program size (pages)		(same as VmSize in status)
resident size of memory portions (pages)	(same as VmRSS in status)
shared   number of pages that are shared	(i.e. backed by a file)
trs      number of pages that are 'code'	(not including libs; broken,
includes data segment)
lrs      number of pages of library		(always 0 on 2.6)
drs      number of pages of data/stack		(including libs; broken,
includes library text)
dt       number of dirty pages			(always 0 on 2.6)
..............................................................................

stat文件关于进程自己更多详细的信息

Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
..............................................................................
Field          Content
pid           process id
tcomm         filename of the executable
state         state (R is running, S is sleeping, D is sleeping in an
uninterruptible wait, Z is zombie, T is traced or stopped)
ppid          process id of the parent process
pgrp          pgrp of the process
sid           session id
tty_nr        tty the process uses
tty_pgrp      pgrp of the tty
flags         task flags
min_flt       number of minor faults
cmin_flt      number of minor faults with child's
maj_flt       number of major faults
cmaj_flt      number of major faults with child's
utime         user mode jiffies
stime         kernel mode jiffies
cutime        user mode jiffies with child's
cstime        kernel mode jiffies with child's
priority      priority level
nice          nice level
num_threads   number of threads 线程数量
it_real_value	(obsolete, always 0)
start_time    time the process started after system boot 进程开始时间
vsize         virtual memory size
rss           resident set memory size
rsslim        current limit in bytes on the rss
start_code    address above which program text can run
end_code      address below which program text can run
start_stack   address of the start of the main process stack
esp           current value of ESP
eip           current value of EIP
pending       bitmap of pending signals
blocked       bitmap of blocked signals
sigign        bitmap of ignored signals
sigcatch      bitmap of catched signals
wchan         address where process went to sleep
0             (place holder)
0             (place holder)
exit_signal   signal to send to parent thread on exit
task_cpu      which CPU the task is scheduled on
rt_priority   realtime priority
policy        scheduling policy (man sched_setscheduler)
blkio_ticks   time spent waiting for block IO
gtime         guest time of the task in jiffies
cgtime        guest time of the task children in jiffies
start_data    address above which program data+bss is placed
end_data      address below which program data+bss is placed
start_brk     address above which program heap can be expanded with brk()
arg_start     address above which program command line is placed
arg_end       address below which program command line is placed
env_start     address above which program environment is placed
env_end       address below which program environment is placed
exit_code     the thread's exit_code in the form reported by the waitpid system call
..............................................................................

1.2 内核数据

和进程的目录结构类似， proc下面可以获取内核信息。

Table 1-5: Kernel info in /proc
..............................................................................
File        Content
apm         Advanced power management info
buddyinfo   Kernel memory allocator information (see text)	(2.5)
bus         Directory containing bus specific information
cmdline     Kernel command line        内核启动命令
cpuinfo     Info about the CPU          cpu信息
devices     Available devices (block and character)   设备包括字符和块设备
dma         Used DMS channels
filesystems Supported filesystems     支持的文件系统
driver	     Various drivers grouped here, currently rtc (2.4) 各种驱动
execdomains Execdomains, related to security			(2.4)
fb	     Frame Buffer devices				(2.4)
fs	     File system parameters, currently nfs/exports	(2.4)
ide         Directory containing info about the IDE subsystem
interrupts  Interrupt usage
iomem	     Memory map						(2.4)
ioports     I/O port usage
irq	     Masks for irq to cpu affinity			(2.4)(smp?)
isapnp	     ISA PnP (Plug&Play) Info				(2.4)
kcore       Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
kmsg        Kernel messages           内核消息
ksyms       Kernel symbol table       内核符号表
loadavg     Load average of last 1, 5 & 15 minutes
locks       Kernel locks
meminfo     Memory info      内存信息
misc        Miscellaneous
modules     List of loaded modules
mounts      Mounted filesystems     挂载的文件系统
net         Networking info (see text)          网络相关
pagetypeinfo Additional page allocator information (see text)  (2.5)
partitions  Table of partitions known to the system
pci	     Deprecated info of PCI bus (new way -> /proc/bus/pci/,
decoupled by lspci					(2.4)
rtc         Real time clock      时钟
scsi        SCSI info (see text)
slabinfo    Slab pool info
softirqs    softirq usage
stat        Overall statistics
swaps       Swap space utilization
sys         See chapter 2
sysvipc     Info of SysVIPC Resources (msg, sem, shm)		(2.4)
tty	     Info of tty drivers
uptime      System uptime
version     Kernel version
video	     bttv info of video resources			(2.4)
vmallocinfo Show vmalloced areas
..............................................................................

可以通过下面看哪些cpu被中断

> cat /proc/interrupts
CPU0
0:    8728810          XT-PIC  timer
1:        895          XT-PIC  keyboard
2:          0          XT-PIC  cascade
3:     531695          XT-PIC  aha152x
4:    2014133          XT-PIC  serial
5:      44401          XT-PIC  pcnet_cs
8:          2          XT-PIC  rtc
11:          8          XT-PIC  i82365
12:     182918          XT-PIC  PS/2 Mouse
13:          1          XT-PIC  fpu
14:    1232265          XT-PIC  ide0
15:          7          XT-PIC  ide1
NMI:          0

伙伴信息

> cat /proc/buddyinfo

Node 0, zone DMA 0 4 5 4 4 3 ...
Node 0, zone Normal 1 0 0 1 101 8 ...
Node 0, zone HighMem 2 0 0 1 1 0 ...内存信息

cat /proc/meminfo

The "Locked" indicates whether the mapping is locked in memory or not.

MemTotal:     16344972 kB
MemFree:      13634064 kB
Buffers:          3656 kB
Cached:        1195708 kB
SwapCached:          0 kB
Active:         891636 kB
Inactive:      1077224 kB
HighTotal:    15597528 kB
HighFree:     13629632 kB
LowTotal:       747444 kB
LowFree:          4432 kB
SwapTotal:           0 kB
SwapFree:            0 kB
Dirty:             968 kB
Writeback:           0 kB
AnonPages:      861800 kB
Mapped:         280372 kB
Slab:           284364 kB
SReclaimable:   159856 kB
SUnreclaim:     124508 kB
PageTables:      24448 kB
NFS_Unstable:        0 kB
Bounce:              0 kB
WritebackTmp:        0 kB
CommitLimit:   7669796 kB
Committed_AS:   100056 kB
VmallocTotal:   112216 kB
VmallocUsed:       428 kB
VmallocChunk:   111088 kB
AnonHugePages:   49152 kB

MemTotal: Total usable ram (i.e. physical ram minus a few reserved
bits and the kernel binary code)
MemFree: The sum of LowFree+HighFree
Buffers: Relatively temporary storage for raw disk blocks
shouldn't get tremendously large (20MB or so)
Cached: in-memory cache for files read from the disk (the
pagecache).  Doesn't include SwapCached
SwapCached: Memory that once was swapped out, is swapped back in but
still also is in the swapfile (if memory is needed it
doesn't need to be swapped out AGAIN because it is already
in the swapfile. This saves I/O)
Active: Memory that has been used more recently and usually not
reclaimed unless absolutely necessary.
Inactive: Memory which has been less recently used.  It is more
eligible to be reclaimed for other purposes
HighTotal:
HighFree: Highmem is all memory above ~860MB of physical memory
Highmem areas are for use by userspace programs, or
for the pagecache.  The kernel must use tricks to access
this memory, making it slower to access than lowmem.
LowTotal:
LowFree: Lowmem is memory which can be used for everything that
highmem can be used for, but it is also available for the
kernel's use for its own data structures.  Among many
other things, it is where everything from the Slab is
allocated.  Bad things happen when you're out of lowmem.
SwapTotal: total amount of swap space available
SwapFree: Memory which has been evicted from RAM, and is temporarily
on the disk
Dirty: Memory which is waiting to get written back to the disk
Writeback: Memory which is actively being written back to the disk
AnonPages: Non-file backed pages mapped into userspace page tables
AnonHugePages: Non-file backed huge pages mapped into userspace page tables
Mapped: files which have been mmaped, such as libraries
Slab: in-kernel data structures cache
SReclaimable: Part of Slab, that might be reclaimed, such as caches
SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
PageTables: amount of memory dedicated to the lowest level of page
tables.
NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
storage
Bounce: Memory used for block device "bounce buffers"
WritebackTmp: Memory used by FUSE for temporary writeback buffers
CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
this is the total amount of  memory currently available to
be allocated on the system. This limit is only adhered to
if strict overcommit accounting is enabled (mode 2 in
'vm.overcommit_memory').
The CommitLimit is calculated with the following formula:
CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
For example, on a system with 1G of physical RAM and 7G
of swap with a `vm.overcommit_ratio` of 30 it would
yield a CommitLimit of 7.3G.
For more details, see the memory overcommit documentation
in vm/overcommit-accounting.
Committed_AS: The amount of memory presently allocated on the system.
The committed memory is a sum of all of the memory which
has been allocated by processes, even if it has not been
"used" by them as of yet. A process which malloc()'s 1G
of memory, but only touches 300M of it will only show up
as using 300M of memory even if it has the address space
allocated for the entire 1G. This 1G is memory which has
been "committed" to by the VM and can be used at any time
by the allocating application. With strict overcommit
enabled on the system (mode 2 in 'vm.overcommit_memory'),
allocations which would exceed the CommitLimit (detailed
above) will not be permitted. This is useful if one needs
to guarantee that processes will not fail due to lack of
memory once that memory has been successfully allocated.
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contiguous block of vmalloc area which is free

..............................................................................

1.4 网络信息

Table 1-9: Network info in /proc/net
..............................................................................
File          Content
arp           Kernel  ARP table
dev           network devices with statistics
dev_mcast     the Layer2 multicast groups a device is listening too
(interface index, label, number of references, number of bound
addresses).
dev_stat      network device status
ip_fwchains   Firewall chain linkage
ip_fwnames    Firewall chain names
ip_masq       Directory containing the masquerading tables
ip_masquerade Major masquerading table
netstat       Network statistics         网络统计
raw           raw device statistics
route         Kernel routing table
rpc           Directory containing rpc info
rt_cache      Routing cache
snmp          SNMP data
sockstat      Socket statistics
tcp           TCP  sockets
udp           UDP sockets
unix          UNIX domain sockets
wireless      Wireless interface data (Wavelan etc)
igmp          IP multicast addresses, which this host joined
psched        Global packet scheduler parameters.
netlink       List of PF_NETLINK sockets
ip_mr_vifs    List of multicast virtual interfaces
ip_mr_cache   List of multicast routing cache
..............................................................................

1.8 内核信息

内核信息可以 通过/proc/stat文件：

> cat /proc/stat
cpu  2255 34 2290 22625563 6290 127 456 0 0
cpu0 1132 34 1441 11311718 3675 127 438 0 0
cpu1 1123 0 849 11313845 2614 0 18 0 0
intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
ctxt 1990473
btime 1062191376
processes 2915
procs_running 1
procs_blocked 0
softirq 183433 0 21755 12 39 1137 231 21459 2263

下面是cpux从左到右每行意思

- user: normal processes executing in user mode
- nice: niced processes executing in user mode
- system: processes executing in kernel mode
- idle: twiddling thumbs
- iowait: waiting for I/O to complete
- irq: servicing interrupts
- softirq: servicing softirqs
- steal: involuntary wait
- guest: running a normal guest
- guest_nice: running a niced guest

2. 每个进程信息

3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj

这个用来调整杀进程用

3.2 /proc/<pid>/oom_score

显示这个分数用来杀进程用的