Integrated: 8255237: ZGC: Bulk free garbage pages during relocation set selection

Per Liden pliden at openjdk.java.net
Mon Nov 2 17:05:03 UTC 2020


On Thu, 22 Oct 2020 12:15:42 GMT, Per Liden <pliden at openjdk.org> wrote:

> During relocation set selection, we immediately free garbage (empty) pages. On very large heap, which has a very high number of garbage pages we can make a significant number of calls to free pages, which prolongs the "Concurrent Select Relocation Set" phase. Freeing a page involves grabbing a lock, inserting the page into the page cache, and then try to satisfy any stalled allocation. By freeing empty pages in bulk, we can amortize the some of the cost of freeing a page and speed up this phase. With this patch we free (up to) 64 pages in bulk.
> 
> This PR depends on "8255234: ZGC: Bulk allocate forwarding data structures" and "8255235: ZGC: Allocate and initialize forwarding data structures in parallel", which are separate PRs (#804 and #805).
> 
> This patch was joint work with Albert (ayang).

This pull request has now been integrated.

Changeset: 3e89f729
Author:    Per Liden <pliden at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/3e89f729
Stats:     168 lines in 7 files changed: 116 ins; 48 del; 4 mod

8255237: ZGC: Bulk free garbage pages during relocation set selection

Co-authored-by: Albert Mingkun Yang <ayang at openjdk.org>
Co-authored-by: Per Liden <pliden at openjdk.org>
Reviewed-by: ayang, eosterlund

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PR: https://git.openjdk.java.net/jdk/pull/806


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