Java HotSpot Virtual Machine

Hi,
My application performance dips significantly when CMS Garbabge Collection is occuring - it seems to be just after the CMS-concurrent-sweep-start debug message. Any ideas about better JVM setting very much appreciated. Further details below.
Thank you.
Kieran.




My Java 1.4.2 settings on a high spec T2000 solaris box with 16G RAM are :

-Xms800m -Xmx800m
-XX:+UseConcMarkSweepGC -XX:+CMSParallelRemarkEnabled
-XX:NewRatio=4
-XX:+UseParNewGC -XX:+DisableExplicitGC
-verbose:gc -XX:+PrintGCTimeStamps -XX:+PrintGCDetails

BTW I THINK NewRatio is ignored with these other settings as New size is 94144K


------------------------------------------------------------------------
There are frequent New GCs so only showing a couple of them and not listing them in trace of CMS at end of this mail.

1160.053: [GC 1160.054: [ParNew: 94080K->0K(94144K), 0.0302041 secs] 397380K->304479K(819136K), 0.0304703 secs]
1162.814: [GC 1162.814: [ParNew: 94080K->0K(94144K), 0.0571286 secs] 398559K->305595K(819136K), 0.0573928 secs]

---------------------------------------------------------------------------------------------------------------

1290.717: [GC [1 CMS-initial-mark: 362526K(724992K)] 362558K(819136K), 0.1275112 secs]
1290.845: [CMS-concurrent-mark-start]
1294.454: [CMS-concurrent-mark: 3.569/3.609 secs]
1294.454: [CMS-concurrent-preclean-start]
1495.246: [CMS-concurrent-preclean: 193.303/200.792 secs]
1495.325: [GC1495.325: [Rescan (parallel) , 0.5435269 secs]1495.869: [weak refs processing, 2.9627689 secs] [1 CMS-remark: 463619K(724992K)] 518093K(819136K), 4.0008904 secs]
1499.326: [CMS-concurrent-sweep-start]
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
// MY application performance dips at this point. CPU usage for
// the java process goes from 4 to 16% busy and application can not handle traffic quickly enough
// !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
1502.295: [CMS-concurrent-sweep: 2.477/2.968 secs]
1502.295: [CMS-concurrent-reset-start]
1502.439: [CMS-concurrent-reset: 0.144/0.144 secs]
1503.044: [GC [1 CMS-initial-mark: 427126K(724992K)] 488757K(819136K), 0.3540072 secs]
1503.398: [CMS-concurrent-mark-start]
1512.465: [CMS-concurrent-mark: 8.144/9.066 secs]
1512.465: [CMS-concurrent-preclean-start]
1918.237: [CMS-concurrent-preclean: 397.660/405.771 secs]
1918.237: [GC1918.238: [Rescan (parallel) , 0.0732901 secs]1918.311: [weak refs processing, 1.5222520 secs] [1 CMS-remark: 625516K(724992K)] 626579K(819136K), 1.7915114 secs]
1920.029: [CMS-concurrent-sweep-start]
1923.836: [CMS-concurrent-sweep: 3.615/3.807 secs]
1923.836: [CMS-concurrent-reset-start]
1923.982: [CMS-concurrent-reset: 0.146/0.146 secs]
1924.632: [GC [1 CMS-initial-mark: 567190K(724992K)] 567206K(819136K), 0.0110855 secs]
1924.643: [CMS-concurrent-mark-start]
1931.535: [CMS-concurrent-mark: 6.745/6.892 secs]
1931.536: [CMS-concurrent-preclean-start]
2259.981: [GC 2259.981: [ParNew (promotion failed): 94080K->94080K(94144K), 1.0813037 secs]2261.062: [CMS2327.230: [CMS-concurrent-preclean: 389.281/395.694 secs]

// MY application performance dips again (even worse) at this stage

Message was edited by:
Kieran.McPeake