Perfect, Tom, thanks.
On Thu, Dec 1, 2011 at 3:21 PM, Tom Rodriguez <tom.rodrig...@oracle.com> wrote: > > On Dec 1, 2011, at 1:34 AM, Charles Oliver Nutter wrote: > >> My recent explorations into Stephen B's perf degradation on JRuby have >> led me to an unfortunate conclusion: something SwitchPoint-related is >> responsible for the remaining slowdown. >> >> I had bugs I fixed, like the awful PIC-causes-repeat-rebinding issue >> or the heavy-class-mutation-never-stabilizes issue, but the last "fix" >> I found was to disable SwitchPoint-based call site invalidation >> entirely. > > The upside of the push based invalidation of SwitchPoint is that the executed > code runs quickly but the downside is that invalidation is expensive, > possibly requiring a deopt and recompilation. If you suspect that's > happening, try running with -XX:+UnlockDiagnosticVMOptions -XX:+LogVMOutput > -XX:+PrintCompilation and look for dependency_failed messages where > type='call_site_target_value'. Any following make_not_entrant messages are > probably caused by the invalidation of the SwitchPoint. > > tom > >> >> Now I'm not (yet) saying this is a perf issue in SwitchPoint itself. >> My problem is that it's very difficult to get any visibility into how >> frequently SwitchPoints are being invalidated (though I could >> instrument my own code, of course), or more importantly how >> drastically those invalidations are affecting performance. Does a >> single SwitchPoint invalidation happening repeatedly completely tank >> performance across the entire system? Does it require SwitchPoint >> invalidation that affects a broader surface area? >> >> I will continue investigating on my side. I suspect the problem is >> that there's just a handful of SwitchPoint locations that are >> repeatedly invalidated, but that those invalidations are having a >> drastic global impact. I'm not yet sure how to work around such a >> situation, where one bad apple is spoiling the whole bunch... >> >> - Charlie >> _______________________________________________ >> mlvm-dev mailing list >> mlvm-dev@openjdk.java.net >> http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev > > _______________________________________________ > mlvm-dev mailing list > mlvm-dev@openjdk.java.net > http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev _______________________________________________ mlvm-dev mailing list mlvm-dev@openjdk.java.net http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev
