frequent major gc but not free heap?

[Bernd]

Hello,

Can you provide a link to a full log file?

>From your description  it sounds like the memory was used, so a full GC
cant free anything. This can either be, that it just take some more time
until it was unused (requested/task ended or transaction timed out) or the
additional tries triggered some soft references or classloaders to be
freed. Hard to say without knowing your applications and having details.

I would suggest you generate a heap dump next time the heap becomes full
(if this is a slow event) or you try to correlate the memory problems with
actual jobs or reqest types (if it happens quickly based on some workload)

Bernd

yuanjun Li <csulyj at gmail.com> schrieb am Mo., 23. Nov. 2015 23:33:

> After running several hours, My http server begin frequenly major gc, but
> no heap was freed.
>
> several times major gc later, promotion failed and concurrent mode failure occured,
> then heap was freed. My gc log is below :
>
> {Heap before GC invocations=7172 (full 720):
>  par new generation   total 737280K, used 667492K [0x000000076b800000, 0x000000079d800000, 0x000000079d800000)
>   eden space 655360K, 100% used [0x000000076b800000, 0x0000000793800000, 0x0000000793800000)
>   from space 81920K,  14% used [0x0000000793800000, 0x00000007943d91d0, 0x0000000798800000)
>   to   space 81920K,   0% used [0x0000000798800000, 0x0000000798800000, 0x000000079d800000)
>  concurrent mark-sweep generation total 1482752K, used 1479471K [0x000000079d800000, 0x00000007f8000000, 0x00000007f8000000)
>  concurrent-mark-sweep perm gen total 131072K, used 58091K [0x00000007f8000000, 0x0000000800000000, 0x0000000800000000)2015-11-19T21:50:02.692+0800: 113963.532: [GC2015-11-19T21:50:02.692+0800: 113963.532: [ParNew (promotion failed)Desired survivor size 41943040 bytes, new threshold 15 (max 15)- age   1:    3826144 bytes,    3826144 total- age   2:     305696 bytes,    4131840 total- age   3:     181416 bytes,    4313256 total- age   4:     940632 bytes,    5253888 total- age   5:      88368 bytes,    5342256 total- age   6:     159840 bytes,    5502096 total- age   7:     733856 bytes,    6235952 total- age   8:      64712 bytes,    6300664 total- age   9:     314304 bytes,    6614968 total- age  10:     587160 bytes,    7202128 total- age  11:      38728 bytes,    7240856 total- age  12:     221160 bytes,    7462016 total- age  13:     648376 bytes,    8110392 total- age  14:      33296 bytes,    8143688 total- age  15:     380768 bytes,    8524456 total: 667492K->665908K(737280K), 0.7665810 secs]2015-11-19T21:50:03.459+0800: 113964.299: [CMS2015-11-19T21:50:05.161+0800: 113966.001: [CMS-concurrent-mark: 3.579/4.747 secs] [Times: user=13.41 sys=0.35, rea
> l=4.75 secs]
>  (concurrent mode failure): 1479910K->44010K(1482752K), 4.7267420 secs] 2146964K->44010K(2220032K), [CMS Perm : 58091K->57795K(131072K)], 5.4939440 secs] [Times: user=9.07 sys=0.13, real=5.49 secs] Heap after GC invocations=7173 (full 721):
>  par new generation   total 737280K, used 0K [0x000000076b800000, 0x000000079d800000, 0x000000079d800000)
>   eden space 655360K,   0% used [0x000000076b800000, 0x000000076b800000, 0x0000000793800000)
>   from space 81920K,   0% used [0x0000000798800000, 0x0000000798800000, 0x000000079d800000)
>   to   space 81920K,   0% used [0x0000000793800000, 0x0000000793800000, 0x0000000798800000)
>  concurrent mark-sweep generation total 1482752K, used 44010K [0x000000079d800000, 0x00000007f8000000, 0x00000007f8000000)
>  concurrent-mark-sweep perm gen total 131072K, used 57795K [0x00000007f8000000, 0x0000000800000000, 0x0000000800000000)}
>
> It seems the CMS GC doesn't make any sense. Could you please explain to
> me ?
>
> This is my gc config:
>
> -server -Xms2248m -Xmx2248m -Xmn800m -XX:PermSize=128m -XX:MaxPermSize=128m -XX:MaxTenuringThreshold=15 -XX:+UseCMSCompactAtFullCollection -XX:CMSFullGCsBeforeCompaction=0 -XX:+UseConcMarkSweepGC -XX:+PrintGCDetails -XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps -Xloggc:gc.log -XX:+PrintHeapAtGC -XX:+PrintTenuringDistribution -XX:+UseFastAccessorMethods
>
>
>
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