RFR: 8254699: Suboptimal PreTouchParallelChunkSize defaults and limits [v2]

[Amit Pawar]

On Wed, 2 Dec 2020 14:36:08 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:

>> I was doubtful about the improvement regarding other platforms and thanks for testing and verifying. I will make it platform-specific as per your suggestion. 
>> 
>> On other platform, this improvement is not seen for smaller or lesser memory range also right ? similar too SPECJbb_Summary sheet in Excel file.
>
> I have not done extensive measurements, I basically ran some startup benchmarks with:
> -XX:+AlwaysPreTouch -Xms8g -Xmx8g
> -XX:+AlwaysPreTouch -Xms8g -Xmx8g -XX:PreTouchParallelChunkSize=4m
> -XX:+AlwaysPreTouch -Xms8g -Xmx8g -XX:PreTouchParallelChunkSize=128m
> 
> And on Windows going with the current default is the clear winner, while on Linux using 4M gives best results. Given that and your tests I think it is fairly safe to use 4M for Linux, but for the other OSes we need to do more measurements before changing to a different value.

OK and I will make it platform specific as suggested.

Thanks,
Amit

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PR: https://git.openjdk.java.net/jdk/pull/1503