RFR: 8261503: Shenandoah: reconsider verifier memory ordering

Wed Feb 10 15:27:44 UTC 2021

On Wed, 10 Feb 2021 11:41:45 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Shenandoah verifier uses lots of atomic operations. Unfortunately, Hotspot's default for atomic operations is memory_order_conservative, which emits two-way memory fences around the CASes at least on AArch64 and PPC64.
> 
> In most cases, that is excessive for verifier, and "relaxed" would do.
> 
> Additional testing:
>  - [x] Linux x86_64 hotspot_gc_shenandoah
>  - [x] Linux AArch64 hotspot_gc_shenandoah
>  - [x] Linux AArch64 tier1 with Shenandoah

Looks good.

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Marked as reviewed by zgu (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/2505