RFR: 8277893: Arraycopy stress tests [v2]

[Aleksey Shipilev]

On Tue, 30 Nov 2021 21:22:09 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Okay. I was concern because of times you show. I am fine with running tests upto 10-15 mins but not this:
>> 
>> # x86_64 (i5-11500)
>>   real    41m32.622s
>>   user    447m19.986s
>>   sys     0m21.026s
>> 
>> 
>> Do you know why it takes so much time on it?
>
> That small machine has very slow memory compared to other ones. The parallelism in stress tests (9 types, 2 forked VMs each) puts that machine on its knees. There is a blurb about that effect here: https://github.com/openjdk/jdk/pull/6594/files#diff-f72fee20a49daaf4e05002372e93f426407ecd429a227393e2ec79e821042c90R40-R47 -- I don't think it would matter much if we trim `MAX_SIZE`, but I'll try tomorrow. Edit: I also remembered that machine also the only AVX-512 capable one in the mix, so the power/frequency mess that AVX-512 is probably does not help, will look into it tomorrow too.

All right. `MAX_SIZE` actually makes a lot of difference for that machine. I trimmed it down to 128K to cater for 64K pages, and added some explanation for the choice. See new commit. Also updated the PR body with new timings.

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PR: https://git.openjdk.java.net/jdk/pull/6594