RFR(S): 8198756: Limit number of compiler threads for small code cache

[Doerr, Martin]

Hi,

the VM currently starts a large amount of compiler threads on systems with many CPUs regardless of the code cache size.
This doesn't make sense for very small code cache sizes.

The dynamically determined number of compiler threads can be observed by:
jdk/bin/java -XX:ReservedCodeCacheSize=128m -XX:+PrintFlagsFinal -version|grep CICompiler

I suggest not to use more than 1 compiler thread per 32MB of code cache:
http://cr.openjdk.java.net/~mdoerr/8198756_CompilerCount/webrev.00/

This seems to be conservative.
Please review and let me know if you have a different limitation proposal.

Best regards,
Martin

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