CODEWITHSUNDEEP
javagarbage-collectionjvm
user1013528
user1013528

Reputation: 93

JVM is not releasing the virtual memroy

My web application is throwing OOM errors. It was given 25GB memory. Application was loaded tested and we see thet memory is ramping up. But I expect the JVM to release the memory after full gc. How come JVM is not releasing the virtual memory even after the application is used.

Here are the JVM settings:

-verbose:gc -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -Xloggc:/logs/gcc.log 
-XX:MaxPermSize=96m -XX:+UseConcMarkSweepGC
-XX:+CMSIncrementalMode -XX:+UseCompressedOops -XX:+UseCompressedStrings
-Xmx30g

Here is the "top" command output: 

top - 02:09:42 up 117 days,  5:24,  4 users,  load average: 0.00, 0.01, 0.05
Tasks: 140 total,   1 running, 139 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:  62167808k total, 60854992k used,  1312816k free,    73444k buffers
Swap:        0k total,        0k used,        0k free, 17789504k cached
    
PID   USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
17206 java     20   0 55.1g  40g  12m S  0.3 68.2 298:41.08 java

Here is the "free" command output: 

             total       used       free     shared    buffers     cached
Mem:      62167808   60855448    1312360          0      73592   17789532
-/+ buffers/cache:   42992324   19175484
Swap:            0          0          0

Please appreciate any leads to fix this issue.

Upvotes: 1

Views: 433

Answers (1)

Alexey Ragozin
Alexey Ragozin

Reputation: 8379

Not all garbage collection algorithms in HotSpot JVM release virtual memory to OS after GC.

Two algorithms which can do it are

  • serial -XX:+UseSerialGC
  • G1 -XX:+UseG1GC

You are using CMS -XX:+UseConcMarkSweepGC which never releases memory to OS.

Here you can find quick summary of all GC algorithms in HotSpot.

Upvotes: 3

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