RFR: 8339387: ZGC: Synchronize medium page allocation
Erik Österlund
eosterlund at openjdk.org
Fri Sep 6 08:25:52 UTC 2024
On Fri, 6 Sep 2024 07:14:11 GMT, Stefan Johansson <sjohanss at openjdk.org> wrote:
> Please review this change to synchronize medium page allocations in ZGC.
>
> **Summary**
> In ZGC objects of a certain size class are allocated in medium sized pages. For each age there is a single medium page shared by all mutators. When this page gets full all thread that try to do a medium page allocation will try to allocate and install a new medium page, but only one will succeed. This can lead to a lot of unnecessary medium page allocation which in turn can lead to the unnecessary page cache flushing.
>
> This change introduces synchronization to only a allow a single thread to allocate the medium page in the common case.
>
> **Testing**
> * Functional testing through mach5 tier1-7 using ZGC
> * Performance testing through aurora to verify no regression occur
> * Manual testing to verify performance
> * Manual testing to verify we avoid page cache flushing
Looks good! Thanks for fixing.
-------------
Marked as reviewed by eosterlund (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/20883#pullrequestreview-2285376634
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