Time stopped is much longer than corresponding Full GC

Y.S.Ramakrishna at Sun.COM Y.S.Ramakrishna at Sun.COM
Fri Mar 27 09:52:36 PDT 2009


Hi Alex --

The bug tracking system informs me that 6546278 was fixed in 5u14
which you appear to be using here. This could be a different
problem or an aspect of the original problem that was somehow
not addressed by the fix in 6546278. I am cc'ing you over to the
hotspot-runtime-dev alias where the necessary expertise exists
to address this issue. I suggest of course  checking if you can
reproduce this problem with the latest 5uXX, as well as, if possible,
the latest OpenJDK 7 JVM. In either event (i.e. if you can
reproduce the problem with either of the latest jvm's listed)
please file a bug with Sun, preferably through your official support
channels for quickest resolution especially when older JDK versions
are involved.

The following additional information may be useful:
(1) the additional JVM option -XX:+PrintSafepointStatistics
     for more visibility into the issue
(2) whether you have lots of native/JNI code in your application.
(3) It is interesting (and puzzling) that you see the issue only
     with the 64-bit JVM. Are all other factors equivalent between your
     32 and 64-bit tests?

thanks.
-- ramki

  On 03/27/09 09:32, Alex Aisinzon wrote:
> Hi all
> 
>  
> 
> I am running tests with Sun JDK 1.5_14 32 and 64 bits. I am using 
> ParallelGC with 2 threads on a Dual Core Opteron 280.
> 
> On the 64 bit one, I see instances whereby the pause times, as reported 
> by the “Total time for which application threads were stopped:” is much 
> longer than the time reported for the full GC.
> 
>  
> 
> Here is an example of this:
> 
>  
> 
> /{Heap before gc invocations=3693:/
> 
> / PSYoungGen      total 2021952K, used 55892K [0x00002aabbf130000, 
> 0x00002aac3f130000, 0x00002aac3f130000)/
> 
> /  eden space 1949248K, 0% used 
> [0x00002aabbf130000,0x00002aabbf130000,0x00002aac360c0000)/
> 
> /  from space 72704K, 76% used 
> [0x00002aac3a7a0000,0x00002aac3de353b0,0x00002aac3eea0000)/
> 
> /  to   space 72576K, 0% used 
> [0x00002aac360c0000,0x00002aac360c0000,0x00002aac3a7a0000)/
> 
> / PSOldGen        total 4194304K, used 4144351K [0x00002aaabf130000, 
> 0x00002aabbf130000, 0x00002aabbf130000)/
> 
> /  object space 4194304K, 98% used 
> [0x00002aaabf130000,0x00002aabbc067c20,0x00002aabbf130000)/
> 
> / PSPermGen       total 204800K, used 122025K [0x00002aaab2930000, 
> 0x00002aaabf130000, 0x00002aaabf130000)/
> 
> /  object space 204800K, 59% used 
> [0x00002aaab2930000,0x00002aaaba05a578,0x00002aaabf130000)/
> 
> /29132.202: [Full GC [PSYoungGen: 55892K->0K(2021952K)] [PSOldGen: 
> 4144351K->2185260K(4194304K)] 4200243K->2185260K(6216256K) [PSPermGen: 
> 122025K->122025K(204800K)], 7.8002190 secs]/
> 
> /Heap after gc invocations=3693:/
> 
> / PSYoungGen      total 2021952K, used 0K [0x00002aabbf130000, 
> 0x00002aac3f130000, 0x00002aac3f130000)/
> 
> /  eden space 1949248K, 0% used 
> [0x00002aabbf130000,0x00002aabbf130000,0x00002aac360c0000)/
> 
> /  from space 72704K, 0% used 
> [0x00002aac3a7a0000,0x00002aac3a7a0000,0x00002aac3eea0000)/
> 
> /  to   space 72576K, 0% used 
> [0x00002aac360c0000,0x00002aac360c0000,0x00002aac3a7a0000)/
> 
> / PSOldGen        total 4194304K, used 2185260K [0x00002aaabf130000, 
> 0x00002aabbf130000, 0x00002aabbf130000)/
> 
> /  object space 4194304K, 52% used 
> [0x00002aaabf130000,0x00002aab4473b2a8,0x00002aabbf130000)/
> 
> / PSPermGen       total 204800K, used 122025K [0x00002aaab2930000, 
> 0x00002aaabf130000, 0x00002aaabf130000)/
> 
> /  object space 204800K, 59% used 
> [0x00002aaab2930000,0x00002aaaba05a578,0x00002aaabf130000)/
> 
> /}/
> 
> /Total time for which application threads were stopped: 15.2489360 seconds/
> 
> /Application time: 7.2144290 seconds/
> 
>  
> 
>  
> 
> I checked on the web and see descriptions of very similar behaviors:
> 
>     * http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6477891
>     * http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6546278
> 
>  
> 
> It remains unclear whether this is fixed in a later release of Sun JDK 1.5.
> 
> If it is indeed the “ 
> <http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=6546278>Synchronization 
> problem in the pseudo memory barrier code”. It may be fixed on JDK 1.7: 
> http://download.java.net/jdk7/changes/jdk7-b15.html
> 
>  
> 
> Our application is currently supported on Sun JDK 1.5 so Sun JDK 1.6 and 
> 1.7, when available, do not constitute good options.
> 
> Should I try to upgrade to the latest of Sun JDK 1.5 or are there 
> “switches” that could make this go away, without sacrificing performance.
> 
> The thing that surprises me most is that is, so far, it occurs only on 
> the 64 bit JVM version.
> 
>  
> 
> Thanks for letting me know
> 
>  
> 
> Alex Aisinzon
> 
>  
> 
> 
> ------------------------------------------------------------------------
> 
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