Jrockit JVM GC issue - weblogic performance and crashes at times

Question

On enabling the verbose gc for memory debug, we have observer the following and we frequently face a JVM issue i.e JVM will be unresponsive due to GC pause and on checking we found the following in GC log.
[memdbg ][Tue Jul 13 01:02:12 2010][26381] GC reason: TLA allocation failed, cause: Get TLA From Nursery
[memdbg ][Tue Jul 13 01:02:12 2010][26381] Stopping of javathreads took 2.234 ms
As of now the following is the TLA size:-
[memdbg ][Tue Jul 13 01:00:10 2010][26381] Minimum TLA size is 2048 bytes
[memdbg ][Tue Jul 13 01:00:10 2010][26381] Preferred TLA size is 65536 bytes
[memdbg ][Tue Jul 13 01:00:10 2010][26381] Large object limit is 2048 bytes
After consultaion with oracle support team, they have asked to us increase the TLA size and we did as follows but we still see the same message.
tried setting
-XXlargeObjectLimit:16k -XXminBlockSize:16k -XXtlaSize:min=16k,preferred=32k
it was still a problem, tried
-XXlargeObjectLimit:32k -XXminBlockSize:32k -XXtlaSize:min=32k,preferred=64k
and we sill the following message.
[memdbg ][Wed Jul 21 03:14:06 2010][11864] f0 3.75Gb
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Minimum TLA size is 16384 bytes
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Preferred TLA size is 32768 bytes
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Large object limit is 16384 bytes
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Minimal blocksize on the freelist is 16384 bytes
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Initial and maximum number of gc threads: 8, of which 8 parallel threads, 4 concurrent threads, and 8 yc threads.
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Preferred free list cache percentage 10%.
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Maximum nursery percentage of free heap is: 95.
[nursery][Wed Jul 21 03:14:06 2010][11864] Optimal nursery size: 536870912, free heap: 1073741824
[nursery][Wed Jul 21 03:14:06 2010][11864] Setting mmNurseryMarker[0] to 0x12affff8
[nursery][Wed Jul 21 03:14:06 2010][11864] Setting mmNurseryMarker[1] to 0x1aaffff0
[nursery][Wed Jul 21 03:14:06 2010][11864] Nursery size increased from 0kb to 524288kb. Parts: 1
[memdbg ][Wed Jul 21 03:14:06 2010][11864] Prefetch distance in balanced tree: 4
[compact][Wed Jul 21 03:14:06 2010][11864] Compactset limit: 7600010, Using matrixes: 0, Static: 0
[memory ][Wed Jul 21 03:14:06 2010][11864] GC mode: Garbage collection optimized for throughput, initial strategy: Generational Parallel Mark & Sweep
[memory ][Wed Jul 21 03:14:06 2010][11864] heap size: 1048576K, maximal heap size: 1048576K, nursery size: 524288K
[memory ][Wed Jul 21 03:14:06 2010][11864] <s>-<end>: GC <before>K-><after>K (<heap>K), <pause> ms
[memory ][Wed Jul 21 03:14:06 2010][11864] <s/start> - start time of collection (seconds since jvm start)
[memory ][Wed Jul 21 03:14:06 2010][11864] <end> - end time of collection (seconds since jvm start)
[memory ][Wed Jul 21 03:14:06 2010][11864] <before> - memory used by objects before collection (KB)
[memory ][Wed Jul 21 03:14:06 2010][11864] <after> - memory used by objects after collection (KB)
[memory ][Wed Jul 21 03:14:06 2010][11864] <heap> - size of heap after collection (KB)
[memory ][Wed Jul 21 03:14:06 2010][11864] <pause> - total sum of pauses during collection (milliseconds)
[memory ][Wed Jul 21 03:14:06 2010][11864] run with -Xverbose:gcpause to see individual pauses
[memdbg ][Wed Jul 21 03:14:39 2010][11864] GC reason: TLA allocation failed, cause: Get TLA From Nursery
[memdbg ][Wed Jul 21 03:14:39 2010][11864] Stopping of javathreads took 1.627 ms
[nursery][Wed Jul 21 03:14:39 2010][11864] KeepAreaStart: 0x1aaffff0 KeepAreaEnd: 0x22b00000
[nursery][Wed Jul 21 03:14:39 2010][11864] Young collection 1 started. This YC is running while the OC is in phase: not running.
[memdbg ][Wed Jul 21 03:14:39 2010][11864] A pinned object was found: 0x11a4d4a0
[memdbg ][Wed Jul 21 03:14:39 2010][11864] A pinned object was found: 0x11a30010
[nursery][Wed Jul 21 03:14:39 2010][11864] Found pinned object: 0x11a4d4a0 - 0x11a4f4b0
Are there any standard tuning recommendations for Jrockit JVM to come over this GC issue? At present, we are using following JAVA options.
-XXlargeObjectLimit:32k -XXminBlockSize:32k -XXtlaSize:min=32k,preferred=64k -verbose:gc -Xverboselog:/tmp/gc.log -Xverbose:memory,gcpause,memdbg,compaction,gc -Xverbosetimestamp -Xgcreport
-RR
Regards
Ranga

Answer 1

If you want to optimize for pausetime, you can use for example
-Xms512m -Xmx512m -Xns256m -XXkeepAreaRatio:25 -Xgcprio:pausetime -XpauseTarget:200msThe parameters xms and xmx can be adjusted to your wishes.