RFR: 8269598: Regressions up to 5% on aarch64 seems due to JDK-8268858

[Joshua Zhu]

On Fri, 16 Jul 2021 02:27:44 GMT, Joshua Zhu <jzhu at openjdk.org> wrote:

>> @JoshuaZhuwj Please try SPECjvm2008 compress on x86/x64 with -XX:+PreserveFramePointer.  We are seeing a regression after JDK-8268858.
>
> @dean-long Thanks for your information. Previously I already found performance degradation with -XX:+PreserveFramePointer in Alibaba Flink Nexmark benchmark. It's caused by inefficient codes generated by RA. That's why I begin working on register pressure. I already created JDK-8270808 [1] to track it. Meanwhile I will also track your mentioned regression issue together with it. Hope they're caused by the same reason.
> 
> [1] https://bugs.openjdk.java.net/browse/JDK-8270808

> @JoshuaZhuwj Please try SPECjvm2008 compress on x86/x64 with -XX:+PreserveFramePointer. We are seeing a regression after JDK-8268858.

Just now I ran six rounds of "compress" on x64 machine with "-XX:+PreserveFramePointer".
Thread number of "compress" test is configured as 1 in my testing environment.
See result at http://cr.openjdk.java.net/~jzhu/8269598/Book2_x86.pdf
There is no regression in my testing. How about yours?

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PR: https://git.openjdk.java.net/jdk/pull/4766