RFR: 8344009: Improve compiler memory statistics

[Roberto Castañeda Lozano]

On Mon, 24 Feb 2025 08:56:51 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>>> @robcasloz I identified and hopefully fixed a small issue that hit the "disabled" path. Turns out we allocate arena chunks a lot more frequently than I thought, and the new unconditional call to Thread::current() in there was hurting a bit. I now avoid this unless I know the statistic is enabled.
>>> 
>>> With this patch, on my machine the difference between unpatched and patched JVM with stats disabled is below one standard deviation for the benchmark in question.
>> 
>> Great, thanks! Will re-run benchmarking and report results early next week.
>
>> > @robcasloz I identified and hopefully fixed a small issue that hit the "disabled" path. Turns out we allocate arena chunks a lot more frequently than I thought, and the new unconditional call to Thread::current() in there was hurting a bit. I now avoid this unless I know the statistic is enabled.
>> > With this patch, on my machine the difference between unpatched and patched JVM with stats disabled is below one standard deviation for the benchmark in question.
>> 
>> Great, thanks! Will re-run benchmarking and report results early next week.
> 
> Functional test results (Oracle tier1-5) still look good for the latest commit (dd7a06ad). I can confirm that the C2 speed regression on our linux-x64 machines is almost fully mitigated. The 2-3% regression on our macosx-aarch64 machines does not seem to be addressed by the latest changes though, but as I mentioned before I think it is in the acceptable range (and only affects one benchmark).

> @robcasloz, @ashu-mehra thanks a lot for your reviews. I incorporated most of them into the PR.

Thanks, Thomas! I see that the changes suggested in https://github.com/openjdk/jdk/commit/d501bd8a674229904358fb168a9c347004efeea3 are not incorporated, is it because you find them out of the scope of this PR? I would argue that at least tagging `Compile::_Compile_types` with `tag_type` is relevant and in line with the other changes included in this PR, e.g. [this one](https://github.com/openjdk/jdk/pull/23530/files#diff-3559dcf23b719805be5fd06fd5c1851dbd8f53e47afe6d99cba13a3de0ebc6b2R443).

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PR Comment: https://git.openjdk.org/jdk/pull/23530#issuecomment-2684893025