RFR(S): 7068240: G1: Long "parallel other time" and "ext root scanning" when running specific benchmark
Y. S. Ramakrishna
y.s.ramakrishna at oracle.com
Thu Jul 21 00:33:33 UTC 2011
Good catch. The changes look good.
On 07/20/11 15:45, John Cuthbertson wrote:
> Hi Everyone,
> Can I have a couple of volunteers look over these changes? The webrev
> can be found at: http://cr.openjdk.java.net/~johnc/7068240/webrev.0/
> When running a specific benchmark, it was noticed that the "ext root
> scanning" time was significantly longer for one thread than the others -
> in a good number of the evacuation pauses. Some of these long times were
> caused by the stack depth on an application thread but others were
> caused by the scanning of the reference processor's discovered lists.
> Furthermore the scanning of the discovered lists was taking place after
> RSet updating and scanning, negating any stealing that might take place
> in these parts, and causing longer termination times. Also the scan
> closures were applied directly to the discovered lists rather than a
> BufferingOopClosure being applied. As a result, if any copying took
> place, the time for that copying was being attributed to ext. root
> scanning rather than "object copying".
> Additionally I also removed a couple statistic variables from
> G1CollectorPolicy that were not thread-local but being updated and
> (overwritten) by the parallel worker threads. The only place where these
> statistic variables were being used was in an instrumentation block that
> was executed when G1PolicyVerbose was set appropriately.
> Testing: gc test suite and jprt.
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