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https://issues.apache.org/jira/browse/CASSANDRA-13034?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Jason Brown updated CASSANDRA-13034:
------------------------------------
Status: Ready to Commit (was: Patch Available)
> Move to FastThreadLocalThread and FastThreadLocal
> -------------------------------------------------
>
> Key: CASSANDRA-13034
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13034
> Project: Cassandra
> Issue Type: Bug
> Reporter: Robert Stupp
> Assignee: Robert Stupp
> Fix For: 3.x
>
>
> (Supersedes/includes CASSANDRA-13033 for 3.X & trunk)
> We still use {{ThreadLocal}} in a couple of places, so I was curious how much
> faster {{FastThreadLocal}} is compared to {{ThreadLocal}}. A micro bench
> tells, that {{FastThreadLocal}} has a runtime of ~2.7ns and {{ThreadLocal}}
> of ~4.7ns - about 2ns slower (EDIT: subtracted baseline).
> However, looking at the implementations it seems that {{ThreadLocal}} has
> more dependent pointer gets than {{FastThreadLocal}}. This (CPU cache misses)
> is not reflected in the artificial benchmark below.
> The patch migrates all {{Thread}} instances (except a few in tests) and all
> {{ThreadLocal}} instances.
> {code:title=FastThreadLocalBench with 4 threads on 4 core CPU}
> [java] FastThreadLocalBench.baseline 2 avgt 5
> 3.023 ± 0.081 ns/op
> [java] FastThreadLocalBench.fastThreadLocal 2 avgt 5
> 5.610 ± 0.154 ns/op
> [java] FastThreadLocalBench.fastThreadLocal 4 avgt 5
> 5.653 ± 0.042 ns/op
> [java] FastThreadLocalBench.fastThreadLocal 8 avgt 5
> 5.763 ± 0.588 ns/op
> [java] FastThreadLocalBench.fastThreadLocal 12 avgt 5
> 5.673 ± 0.117 ns/op
> [java] FastThreadLocalBench.threadLocal 2 avgt 5
> 7.708 ± 0.723 ns/op
> [java] FastThreadLocalBench.threadLocal 4 avgt 5
> 7.604 ± 0.059 ns/op
> [java] FastThreadLocalBench.threadLocal 8 avgt 5
> 7.629 ± 0.080 ns/op
> [java] FastThreadLocalBench.threadLocal 12 avgt 5
> 7.858 ± 0.483 ns/op
> {code}
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