checkpoint性能测试

--checkpoint各参数的值
checkpoint_segments 最多的wal log数量，到达后会激发checkpoint，通常设定在30就好
checkpoint_timeout 一般设置15-20分钟，常的可以设定1天也没关系
checkpoint_completion_target 这个保持不动就好。内建是0.5，意思就是每个checkpoint预计在下个checkpoint完成前的一半时间内完成（听起来有点绕嘴，呵呵）
checkpoint_warning 如果checkpint速度快于这个时间，在log中记录。内建是30秒

select name,setting,context,vartype,source from pg_settings where name like 'checkpoint%';
name             | setting | context | vartype |       source
------------------------------+---------+---------+---------+--------------------
checkpoint_completion_target | 0.5     | sighup  | real    | default
checkpoint_segments          | 16      | sighup  | integer | configuration file
checkpoint_timeout           | 300     | sighup  | integer | default
checkpoint_warning           | 30      | sighup  | integer | default

--新增测试表和函数.
create table test (id int primary key, info text, crt_time timestamp);

create or replace function f_id_add(i_id int) returns void as $$
declare
begin
update test set crt_time=clock_timestamp() where id=i_id;
if not found then
insert into test values (i_id,md5(random()::text),clock_timestamp());
return;
else
return;
end if;
return;
exception when others then
return;
end;
$$ language plpgsql strict;

--测试脚本
vi test.sql
\setrandom id 1 5000000
select * from f_id_add(:id);

--测试
pgbench -M prepared -f ./test.sql -n -r -c 6 -j 6 -T 600

checkpoint_segments=2

[postgres@rudy ~]$ pgbench -M prepared -f ./test.sql -n -r -c 6 -j 6 -T 600
transaction type: Custom query
scaling factor: 1
query mode: prepared
number of clients: 6
number of threads: 6
duration: 600 s
number of transactions actually processed: 984350
tps = 1637.193339 (including connections establishing)
tps = 1648.603223 (excluding connections establishing)
--可以看到tps为1600左右，且系统中有大量的磁盘IO,每隔几秒

----total-cpu-usage---- -dsk/total- ------memory-usage----- ---paging-- -net/total- ----swap--- ---system-- --io/total- ---file-locks-- --sysv-ipc-
usr sys idl wai hiq siq| read  writ| used  buff  cach  free|  in   out | recv  send| used  free| int   csw | read  writ|pos lck rea wri|msg sem shm
1   0   0  99   0   0|   0  2440k| 320M 3236k  596M 70.5M|   0     0 | 618B  824B| 624M 3376M| 399   400 |   0   236 |227 5.0   0 232|  0  69  18
0   1   0  98   0   1| 220k 2824k| 320M 3236k  596M 70.2M|   0     0 |   0     0 | 624M 3376M| 441   426 |12.0   266 |227 5.0   0 232|  0  69  18
1   1   0  98   0   0| 208k 3696k| 319M 3236k  596M 70.2M|   0     0 |  60B 1174B| 624M 3376M| 450   429 |3.00   321 |227 5.0   0 232|  0  69  18
5   6   0  90   0   0|  68k 7928k| 319M 3276k  597M 68.9M|   0     0 | 120B  844B| 624M 3376M| 780  3258 |5.00   584 |227 5.0   0 232|  0  69  18
30  44   0  23   1   1|   0    15M| 319M 3276k  604M 61.8M|   0     0 |  60B  678B| 624M 3376M|1873    22k|   0  1196 |227 5.0   0 232|  0  69  18
25  48   0  25   3   0|   0    13M| 319M 3268k  599M 68.0M|   0   492k|  60B  662B| 625M 3375M|1901    23k|   0  1214 |227 5.0   0 232|  0  69  18
35  39   0  22   3   1| 128k   12M| 318M 3280k  598M 69.8M|   0   788k|  60B  662B| 626M 3374M|1716    19k|1.00  1040 |227 5.0   0 232|  0  69  18
51  29   0  19   0   1|   0    34M| 317M 3280k  599M 69.4M|   0   108k|  60B  678B| 626M 3374M|1649    17k|   0   967 |227 5.0   0 232|  0  69  18
19  17   0  58   2   4|4096B   32M| 318M 3284k  603M 64.7M|   0  1300k|  60B  662B| 627M 3373M|1328  8586 |1.00   898 |227 5.0   0 232|  0  69  18
9  18   0  64   0   9|4096B   17M| 317M 3288k  598M 70.6M|   0     0 |  60B  678B| 627M 3373M|  97   185 |1.00   100 |227 5.0   0 232|  0  69  18
1   1   0  97   0   0|   0  4780k| 317M 3292k  598M 70.6M|   0     0 |  60B  678B| 627M 3373M| 515   423 |   0   443 |227 5.0   0 232|  0  69  18

checkpoint_segments=16

[postgres@rudy ~]$ pgbench -M prepared -f ./test.sql -n -r -c 6 -j 6 -T 600
transaction type: Custom query
scaling factor: 1
query mode: prepared
number of clients: 6
number of threads: 6
duration: 600 s
number of transactions actually processed: 1333210
tps = 2221.020258 (including connections establishing)
tps = 2221.203625 (excluding connections establishing)
--可以看到tps为2200左右，且系统中磁盘io没有之前频繁
----total-cpu-usage---- -dsk/total- ------memory-usage----- ---paging-- -net/total- ----swap--- ---system-- --io/total- ---file-locks-- --sysv-ipc-
usr sys idl wai hiq siq| read  writ| used  buff  cach  free|  in   out | recv  send| used  free| int   csw | read  writ|pos lck rea wri|msg sem shm
22  52   0  25   1   0|  24k 9024k| 259M 3032k  658M 68.9M|   0     0 |  60B  828B| 682M 3318M|1887    22k|3.00  1180 |227 5.0   0 232|  0  69  18
42  32   0  22   3   1|8192B 9024k| 259M 3032k  659M 67.7M|   0     0 | 120B 1756B| 682M 3318M|1942    23k|1.00  1169 |227 5.0   0 232|  0  69  18
46  29   0  24   1   0| 200k 8600k| 259M 3032k  660M 66.4M|   0     0 |  60B  678B| 682M 3318M|1942    21k|9.00  1122 |227 5.0   0 232|  0  69  18
32  45   0  22   1   0|   0  9224k| 259M 3032k  662M 65.2M|   0     0 |  60B  678B| 682M 3318M|1955    23k|   0  1198 |227 5.0   0 232|  0  69  18
21  51   0  27   0   1|  84k 8768k| 259M 3032k  663M 64.0M|   0     0 |  60B  662B| 682M 3318M|1876    22k|9.00  1153 |227 5.0   0 232|  0  69  18
12  31   0  54   1   1|8192B   28M| 260M 3032k  663M 62.5M|   0     0 |  60B  678B| 682M 3318M|1250    12k|1.00   800 |227 5.0   0 232|  0  69  18
1   2   0  94   1   1|   0    14M| 260M 3032k  663M 62.5M|   0     0 |  60B  678B| 682M 3318M| 754   570 |   0   542 |227 5.0   0 232|  0  69  18
1   1   0  98   0   0|   0  6920k| 260M 3032k  663M 62.5M|   0     0 |  60B  812B| 682M 3318M| 566   518 |   0   373 |227 5.0   0 232|  0  69  18
1   0   0  98   0   1|   0  6088k| 260M 3032k  663M 62.5M|   0     0 |  60B  662B| 682M 3318M| 546   486 |   0   348 |227 5.0   0 232|  0  69  18
1   0   0  99   0   0|   0  8032k| 260M 3032k  663M 62.5M|   0     0 |  60B  662B| 682M 3318M| 664   532 |   0   448 |227 5.0   0 232|  0  69  18
1   1   0  98   0   0|   0  4952k| 260M 3032k  664M 62.4M|   0     0 | 120B  704B| 682M 3318M| 535   540 |   0   359 |227 5.0   0 232|  0  69  18
1   1   0  98   0   0|   0  6596k| 260M 3032k  664M 62.5M|   0     0 |  60B  662B| 682M 3318M| 651   511 |   0   499 |227 5.0   0 232|  0  69  18
1   1   0  97   1   0|   0  6968k| 260M 3032k  664M 62.5M|   0     0 |  60B  662B| 682M 3318M| 677   575 |   0   543 |227 5.0   0 232|  0  69  18
3   6   0  90   0   1|  16k 8852k| 260M 3048k  664M 62.4M|   0     0 |  60B  662B| 682M 3318M| 902  2627 |2.00   697 |227 5.0   0 232|  0  69  18
20  60   0  17   2   2|8192B 9968k| 260M 3048k  665M 61.1M|   0     0 |  60B  678B| 682M 3318M|2019    24k|1.00  1309 |227 5.0   0 232|  0  69  18
22  43   0  31   3   0|   0  8632k| 260M 3048k  666M 60.0M|   0     0 |  60B  678B| 682M 3318M|1774    22k|   0  1117 |227 5.0   0 232|  0  69  18
53  32   0  13   1   1|   0    10M| 259M 3044k  656M 69.9M|   0     0 |  60B  662B| 682M 3318M|2251    25k|   0  1331 |227 5.0   0 232|  0  69  18
42  42   0  15   1   0|   0  9808k| 259M 3044k  658M 69.2M|   0     0 |  60B  662B| 682M 3318M|2137    24k|   0  1292 |227 5.0   0 232|  0  69  18

--checkpint信息查看
SELECT (100 * checkpoints_req) / (checkpoints_timed + checkpoints_req) AS checkpoints_req_pct,
pg_size_pretty(buffers_checkpoint * block_size / (checkpoints_timed + checkpoints_req)) AS avg_checkpoint_write,
pg_size_pretty(block_size * (buffers_checkpoint + buffers_clean + buffers_backend)) AS total_written,
100 * buffers_checkpoint / (buffers_checkpoint + buffers_clean + buffers_backend) AS checkpoint_write_pct,
100 * buffers_backend / (buffers_checkpoint + buffers_clean + buffers_backend) AS backend_write_pct,
*
FROM pg_stat_bgwriter,
(SELECT cast(current_setting('block_size') AS integer) AS block_size) AS bs;