static callCount field used for "every 256 calls" thread event polling
interferes with parallelization
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Key: JRUBY-2344
URL: http://jira.codehaus.org/browse/JRUBY-2344
Project: JRuby
Issue Type: Bug
Affects Versions: JRuby 1.1
Reporter: Charles Oliver Nutter
Assignee: Charles Oliver Nutter
Priority: Blocker
Fix For: JRuby 1.1+
In our inline caching CallSite, there is an integer callCount field that
increments on each call. When the callCount % 255 == 0, it polls for thread
events. This was added to match Ruby's similar behavior for determining thread
rescheduling. However with this field static on CallSite, a benchmark done at
Sun shows that threads do not appropriately parallelize, actually running
slower with multiple threads than with a single thread.
Moving the call count into ThreadContext as a field appears to resolve the
issue, so there must be some JVM weirdness happening with static mutable fields
used for branching. I will make the appropriate change.
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