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From "Caldarale, Charles R" <Chuck.Caldar...@unisys.com>
Subject RE: Redeploy leaks
Date Tue, 06 Jan 2009 15:59:36 GMT
> From: Martin Gainty [mailto:mgainty@hotmail.com]
> Subject: RE: Redeploy leaks
>
> > http://community.eapps.com/showthread.php?t=153
> MG>good link to illustrate PermGen settings but including
> class objects in sweep for recovering PermGen should be a
> last MG>resort

Note that the above article applies only when the concurrent mark-sweep (CMS) GC algorithm
is in effect, which is *not* the default.  CMS can be manually enabled via the command line
parameter:
  -XX:+UseConcMarkSweepGC
or one of its aliases (-Xincgc, -Xconcgc).

The CMS algorithm will also be invoked if UseAutoGCSelectPolicy is set and MaxGCPauseMillis
is explicitly set to a value less than or equal to AutoGCSelectPauseMillis, whose default
value is 5000 (the Java SE 6 release notes say 1 second, but the code says 5).

Unless you have extremely stringent response time requirements, you probably don't want to
enable CMS; it reduces throughput, and normal parallel GCs these days are usually fast enough
not to create a noticeable hiccup.

 - Chuck


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