[9, 8u40] RFR (XS): 8068915: uncommon trap w/ Reason_speculate_class_check causes performance regression due to continuous deoptimizations

John Rose john.r.rose at oracle.com
Fri Jan 16 23:27:31 UTC 2015

On Jan 16, 2015, at 10:34 AM, Vladimir Ivanov <vladimir.x.ivanov at oracle.com> wrote:
> http://cr.openjdk.java.net/~vlivanov/8068915/webrev.00
> https://bugs.openjdk.java.net/browse/JDK-8068915
> The fix for 8063137 [1] (just sent out for review) uncovered another issue with deoptimization counts pollution. In some cases, speculative traps can stuck continuously deoptimizing and never reach recompilation. Usually, it ruins performance if it happens.

Good; reviewed.

While you are in graphKit.cpp, it would be nice to remove this not-reached line:
  http://hg.openjdk.java.net/jdk9/dev/hotspot/file/f35435a37581/src/share/vm/opto/graphKit.cpp#l2176 <http://hg.openjdk.java.net/jdk9/dev/hotspot/file/f35435a37581/src/share/vm/opto/graphKit.cpp#l2176>

— John
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