Integrated: 8259231: Epsilon: improve performance under contention during virtual space expansion

[Lehua Ding]

On Wed, 16 Dec 2020 01:29:55 GMT, Lehua Ding <github.com+13173904+lhtin at openjdk.org> wrote:

> Hi all,
> 
> The `EpsilonHeap::allocate_work` method maybe can be fixed and improved by this:
> 1. it can prevent allocate failure by retry `_space->par_allocate` before expanding virtual space,  when there not enough virtual space but another thread expanding succeeded just and has enough space.
> 2. it can reduce the lock time by move `res = _space->par_allocate(size);` out of lock scope.
> 
> Test on macosx-x86_64-server-{release, fastdebug, slowdebug} with current test case.

This pull request has now been integrated.

Changeset: 722f2361
Author:    Lehua Ding <lehuading at tencent.com>
Committer: Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/722f2361
Stats:     39 lines in 1 file changed: 17 ins; 4 del; 18 mod

8259231: Epsilon: improve performance under contention during virtual space expansion

Reviewed-by: shade

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PR: https://git.openjdk.java.net/jdk/pull/1794