A really weird GC problem (long GC pause)

[Vitaly Davidovich]

Usually when you see things like this (low user and sys time but high real)
it's because of heavy swapping.  You mention that you use 16gb out of 32
but is there nothing else running on this machine that could be tying up
memory? This should be ruled out first, I'd say.

Sent from my phone
On Jul 12, 2012 1:42 PM, "Zhenghua Gao" <docete at gmail.com> wrote:

> We run a Hbase cluster on ordinary machines (8 cores, 32GB memory).
> Our RegionServer takes 16 GB (heap size) memory, and young GC takes less
> than 1 second normally.
> However, every now and then there is some periods that young GC may takes
> hundreds seconds.
>
> We have 16GB heap size, and use ParNew and CMS for GC. The GC log is
> listed below:
>
> 2012-07-11T19:41:00.387+0800: 12391.954: [GC Before GC:
> Statistics for BinaryTreeDictionary:
> ------------------------------------
> Total Free Space: 1200692977
> Max   Chunk Size: 1200692977
> Number of Blocks: 1
> Av.  Block  Size: 1200692977
> Tree      Height: 1
> Before GC:
> Statistics for BinaryTreeDictionary:
> ------------------------------------
> Total Free Space: 1465991
> Max   Chunk Size: 1464832
> Number of Blocks: 4
> Av.  Block  Size: 366497
> Tree      Height: 3
> 13209.843: [ParNew13209.911: [SoftReference, 0 refs, 0.0000120
> secs]13209.911: [WeakReference, 93 refs, 0.0000150 secs]13209.911:
> [FinalReference, 271 refs, 0.0009130 secs]13209.912: [PhantomReference, 10
> refs, 0.0000110 secs]13209.912: [JNI Weak Reference, 0.0000030 secs]
> Desired survivor size 26836992 bytes, new threshold 1 (max 15)
> - age   1:   39360920 bytes,   39360920 total
> : 471872K->52416K(471872K), 0.0692990 secs]
> 7343322K->6979157K(16724800K)After GC:
> Statistics for BinaryTreeDictionary:
> ------------------------------------
> Total Free Space: 1193619699
> Max   Chunk Size: 1193619699
> Number of Blocks: 1
> Av.  Block  Size: 1193619699
> Tree      Height: 1
> After GC:
> Statistics for BinaryTreeDictionary:
> ------------------------------------
> Total Free Space: 1465991
> Max   Chunk Size: 1464832
> Number of Blocks: 4
> Av.  Block  Size: 366497
> Tree      Height: 3
> , 0.0695400 secs] [Times: user=0.47 sys=0.12, real=818.01 secs]
>
> Is there any clue that i can solve this issue? Thanks.
>
> _______________________________________________
> hotspot-gc-use mailing list
> hotspot-gc-use at openjdk.java.net
> http://mail.openjdk.java.net/mailman/listinfo/hotspot-gc-use
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mail.openjdk.java.net/pipermail/hotspot-gc-use/attachments/20120712/c57a8253/attachment.html