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From Peter Schuller <>
Subject Re: ParNew and caching
Date Sat, 10 Dec 2011 19:10:18 GMT
> After re-reading my post, what I meant to say is that I switched from
> Serializing cache provider to ConcurrentLinkedHash cache provider and then
> saw better performance, but still far worse than no caching at all:
> - no caching at all : 25-30ms
> - with Serializing provider : 1300+ms
> - with Concurrent provider : 500ms
> 100% cache hit rate.  ParNew is the only stat that I see out of line, so
> seems like still a lot of copying

In general, if you want to get to the bottom of this stuff and you
think GC is involved, always run with -XX:+PrintGC -XX:+PrintGCDetails
-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps so that the GC activity
can be observed.

1300+ should not be GC unless you are having fallbacks to full GC:s
(would be possible to see with gc logging) and it should definitely be
possible to avoid full gc:s being extremely common (but eliminating
them entirely may not be possible).

/ Peter Schuller (@scode,

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