Java 500M的表，约1千万的数据放在HashMap里面大约占用内存多大？给多大内存最保险？

测试1、给 java -Xms2048m -Xmx2048m

[code=plain]GC:  Scavenge GC - Reason started:  Eden full - parallel with thread number:  8
GC:  Scav 7.613 s  Since start of previous GC: 7.613 s  GC time: 0.572 s
Time spent executing application: 7.613 s  (93.02%)
Object size causing failure: 48 bytes  MaxTenure: 7
Eden: 536870912->48/536870912
Survivor: 0->88072136/88080384 (survivor used: 99.99%)
Old: 0->410543440/1434451968       (old used: 28.62%)
Perm: 10869592->10869592/10911744
GC:  Full GC - Reason started:  Allocation failure
GC:  Full 14.852 s  Since start of previous GC: 7.239 s  GC time: 12.318 s
Time spent executing application: 6.667 s  (35.12%)
**** WARNING: Too much time spent in GC (>20%)
Object size causing failure: 40 bytes  MaxTenure: 7
Eden: 536870912->40/536870912
Survivor: 88072136->0/88080384 (survivor used: 0.00%)
Old: 410543440->1004089160/1434451968       (old used: 70.00%)
Perm: 10870672->10870672/10977280
GC:  Full GC - Reason started:  Allocation failure
GC:  Full 32.144 s  Since start of previous GC: 17.291 s  GC time: 9.114 s
Time spent executing application: 4.974 s  (35.31%)
**** WARNING: Too much time spent in GC (>20%)
Object size causing failure: 152 bytes  MaxTenure: 7
Eden: 536870912->72980680/536870912
Survivor: 0->0/88080384 (survivor used: 0.00%)
Old: 1004089160->1434417264/1434451968       (old used: 100.00%)
**** WARNING: Sufficient Old Space not reclaimed (<20%)

测试2、给 java -Xms8092m -Xmx8092m

[code=plain]GC:  Scavenge GC - Reason started:  Eden full - parallel with thread number:  8
GC:  Scav 35.977 s  Since start of previous GC: 35.977 s  GC time: 2.516 s
Time spent executing application: 35.977 s  (93.46%)
Object size causing failure: 32 bytes  MaxTenure: 7
Eden: 2147483648->32/2147483648
Survivor: 0->356483168/356515840 (survivor used: 99.99%)
Old: 0->1583995632/5729419264       (old used: 27.65%)
Perm: 10872000->10872000/10977280
GC:  Scavenge GC - Reason started:  Eden full - parallel with thread number:  8
GC:  Scav 72.401 s  Since start of previous GC: 36.424 s  GC time: 3.535 s
Time spent executing application: 33.908 s  (90.56%)
Object size causing failure: 104 bytes  MaxTenure: 7
Eden: 2147483648->104/2147483648
Survivor: 356483168->356491160/356515840 (survivor used: 99.99%)
Old: 1583995632->3541143400/5729419264       (old used: 61.81%)
Perm: 10873672->10873672/10977280
$

[code=plain] map's size is 13318240 finshed!, totally used 86229 millionseconds ##处理完成约需要86秒左右

总结：