[jdk18] RFR: 8279597: [TESTBUG] ReturnBlobToWrongHeapTest.java fails with -XX:TieredStopAtLevel=1 on machines with many cores

[Hao Sun]

On Tue, 11 Jan 2022 17:30:24 GMT, Vladimir Kozlov <kvn at openjdk.org> wrote:

> There is specific code to take into account CodeCache size when we calculate number of compiler thread: https://github.com/openjdk/jdk18/blob/master/src/hotspot/share/compiler/compilationPolicy.cpp#L450
> 
> Can you check why it does not work?

Thanks a lot for your review.

It doesn't work because the check at https://github.com/openjdk/jdk18/blob/master/src/hotspot/share/compiler/compilationPolicy.cpp#L461 fails.
In my local test machine(with 224 cores), `count` equals to 21, but `max_count` equals to 28 (Note that `ReservedCodeCacheSize` is 16M, `CodeCacheMinimumUseSpace` is 400K and `buffer_size` is 576,716).


> 
> There is also possibility that number of compiler threads increase dynamically which is guarded by `-XX:+UseDynamicNumberOfCompilerThreads` flag. Try to switch it off in this test.

I tried to switch it off, but the test still failed.

> You can also set small value with `-XX:CICompilerCount=n' for this test. Increasing CodeCachecsize to 64M may help your case but we can have machines with core count even larger.

Yes. Agree. I think your solution would be better.
Will test more and update soon. Thanks.

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PR: https://git.openjdk.java.net/jdk18/pull/93