RFR: 8268127: Shenandoah: Heap size may be too small for region to align to large page size [v4]

[Roman Kennke]

On Mon, 7 Jun 2021 13:04:41 GMT, Zhengyu Gu <zgu at openjdk.org> wrote:

>> TestLargePages.java failed on Linux AArch64, where large page size is 500M, and the test is configured to run with much smaller heap, e.g. 131M.
>> 
>> This is *not* AArch64 specific, just none of our regular test machines has large page setup.
>> 
>> I purpose two invariants:
>> 1) Heap size always aligns up to page size that is requested.
>> 2) Region size always aligns up to page size that is requested if heap is large enough to accommodate them. Otherwise, it aligns up to regular page size.
>> 
>> This partially reverts JDK-8266802.
>> 
>> Obviously, this is a corner case and is unlikely seen in real word. The alternative is to disable UseLargePages if heap size is too small, e.g. align_up(heap_size, page_size) < MIN_NUM_REGIONS.
>> 
>> Test:
>>   hotspot_gc_shenandoah
>
> Zhengyu Gu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains six additional commits since the last revision:
> 
>  - rkennke's comment
>  - Merge branch 'master' into JDK-8268127-large-page-small-heap
>  - Window build
>  - Fix compilation error
>  - v2
>  - v1

Marked as reviewed by rkennke (Reviewer).

-------------

PR: https://git.openjdk.java.net/jdk/pull/4320