RFR: 8276618: Pad cacheline for Thread::_rcu_counter

[Thomas Schatzl]

On Thu, 4 Nov 2021 05:09:48 GMT, Hamlin Li <mli at openjdk.org> wrote:

> Currently, Thread::_rcu_counter is not padded by cacheline, it should be beneficail to do so.
> 
> The initial spebjbb test shows about 10.5% improvement of critical, and 0.7% improvement of max in specjbb2015, specjbb arguments:
>   GROUP_COUNT=4
>   TI_JVM_COUNT=1
>   JAVA_OPTS_BE="-server -XX:+UseG1GC -Xms32g -Xmx32g"
>   MODE_ARGS="-ikv"

I'll push it through our perf testing.

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PR: https://git.openjdk.java.net/jdk/pull/6246