Java到底占用多大内存？

Java到底占用多大内存？

在我们64位的CenterOS上，指定了JVM的最大堆内存为5500M，但是在top和进程status中可以看到实际占用内存已经远远大于5500M，那么JVM到底占用多大内存？如果做到控制JVM的占用内存大小？

root      21042   74.8   86.4   11194944   7072088   ?     Sl   Dec17  6818 : 07   / opt / j2sdk / bin / java  - server
- Xms5500M  - Xmx5500M  - Xmn2000M  - Xss128k  - XX:PermSize = 256m  - XX:MaxPermSize = 512m  - XX: + UseParNewGC
- XX:ParallelGCThreads = 8   - XX:SurvivorRatio = 6   - XX:TargetSurvivorRatio = 90   - XX:MaxTenuringThreshold = 30
- XX:SoftRefLRUPolicyMSPerMB = 0   - XX: + UseAdaptiveSizePolicy  - XX: + UseConcMarkSweepGC  - XX: + CMSIncrementalMode
  - XX: + UseCMSCompactAtFullCollection  - XX:CMSFullGCsBeforeCompaction = 5   - XX:CMSInitiatingOccupancyFraction = 55
  - XX:CMSIncrementalSafetyFactor = 20   - XX: + PrintGCDetails  - XX: + PrintGCTimeStamps
- Djmagick.systemclassloader = false   - DXCE_USE_DBCP  - Djava.library.path =/ opt / resin / libexec: / opt / j2sdk / lib: / usr / lib64
- DPASSPORT_CREATE_CLUSTER  - Dresin.home =/ opt / resin  - Dserver.root =/ opt / resin
- Djava.util.logging.manager = com.caucho.log.LogManagerImpl
- Djavax.management.builder.initial = com.caucho.jmx.MBeanServerBuilderImpl
com.caucho.server.resin.Resin  - socketwait  52840   - stdout  / opt / resin / log / stdout.log  - stderr  / opt / resin / log / stderr.log

top  -   19 : 45 : 42  up  247  days,   7 : 42 ,   3  users,  load average:  2.26 ,  2.30 ,  1.97
Tasks:  125  total,    1  running,  124  sleeping,    0  stopped,    0  zombie
Cpu(s):   8.7 % us,   2.9 % sy,   0.0 % ni,  87.6 % id,   0.0 % wa,   0.0 % hi,   0.7 % si,   0.0 % st
Mem:   8182228k total,  8125820k used,    56408k free,   110572k buffers
Swap:  4192956k total,  1844992k used,  2347964k free,   435444k cached

  PID USER      PR  NI  VIRT  RES  SHR S  % CPU  % MEM    TIME +   COMMAND
21042  root       25     0   10 .6g  6 .7g  4680  S  95.2   86.4     6817 : 21  java

[root@xxxxxx ~ ]# cat  / proc / 21042 / status
Name:   java
State:  S (sleeping)
SleepAVG:        0 %
Tgid:    21042
Pid:     21042
PPid:    21040
TracerPid:       0
Uid:     0         0         0         0
Gid:     0         0         0         0
FDSize:  8192
Groups:  0   1   2   3   4   6   10
VmPeak:  11260480  kB
VmSize:  11194944  kB
VmLck:          0  kB
VmHWM:    7257276  kB
VmRSS:    7073852  kB
VmData:  11095496  kB
VmStk:         84  kB
VmExe:         36  kB
VmLib:      68124  kB
VmPTE:      20860  kB
StaBrk: 5da65000 kB
Brk:    61fcf000 kB
StaStk: 7fffa59d3cd0 kB
Threads:         26825
SigQ:    0 / 69632
SigPnd:  0000000000000000
ShdPnd:  0000000000000000
SigBlk:  0000000000000000
SigIgn:  0000000000000001
SigCgt: 1000000181005cce
CapInh:  0000000000000000
CapPrm: 00000000fffffeff
CapEff: 00000000fffffeff
Cpus_allowed:    00000000 , 00000000 , 00000000 , 00000000 , 00000000 , 00000000 , 00000000 ,000000ff
Mems_allowed:    00000000 , 00000001

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