Integrated: 8268127: Shenandoah: Heap size may be too small for region to align to large page size

[Zhengyu Gu]

On Wed, 2 Jun 2021 20:47:32 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

This pull request has now been integrated.

Changeset: 5ad4a91c
Author:    Zhengyu Gu <zgu at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/5ad4a91c3d89f7118a99e5bd56fc86a9a6d57abf
Stats:     33 lines in 3 files changed: 20 ins; 0 del; 13 mod

8268127: Shenandoah: Heap size may be too small for region to align to large page size

Reviewed-by: rkennke, shade

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