8268372: ZGC: dynamically select the number of concurrent GC threads used

[albertnetymk]

This patch adds support for dynamically selecting the number of GC threads to ZGC.

1. The number of GC threads (in [1, ConcGCThreads]) is dynamically selected for each GC cycle.
2. Increase the default value of ConcGCThreads from 12.5% to 25% of total CPUs.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed

Issue

• JDK-8268372: ZGC: dynamically select the number of concurrent GC threads used

Reviewers

• Per Liden (@pliden - Reviewer)
• Erik Österlund (@fisk - Reviewer)

Contributors

• Per Liden <pliden@openjdk.org>

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/4410/head:pull/4410
$ git checkout pull/4410

Update a local copy of the PR:
$ git checkout pull/4410
$ git pull https://git.openjdk.java.net/jdk pull/4410/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 4410

View PR using the GUI difftool:
$ git pr show -t 4410

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/4410.diff

[bridgekeeper]

👋 Welcome back ayang! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@albertnetymk The following label will be automatically applied to this pull request:

• hotspot-gc

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

[mlbridge]

Webrevs

• 00: Full (d0ef6fde)

[openjdk]

@albertnetymk This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8268372: ZGC: dynamically select the number of concurrent GC threads used

Co-authored-by: Per Liden <pliden@openjdk.org>
Reviewed-by: pliden, eosterlund

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 20 new commits pushed to the master branch:

• 159cb6f: 8268083: JDK-8267706 breaks bin/idea.sh on a Mac
• 8158b82: 8268327: Upstream: 8268169: The system lookup can not find stdio functions such as printf on Windows 10
• 6843576: 8268227: java/foreign/TestUpcall.java still times out
• 2717fcb: 8232948: javac -h should mangle the overload argument signature
• 89da202: 8266159: macOS ARM + Metal pipeline shows artifacts on Swing Menu with Java L&F
• 61ab4b9: 8267564: JDK-8252971 causes SPECjbb2015 socket exceptions on Windows when MKS is installed
• 00c88f7: 8266918: merge_stack in check_code.c add NULL check
• 8105478: 8268165: AsyncLogging will crash if rotate() fails
• fd91b2a: 8265440: IGV: make node selection more visible
• 81bad59: 8257774: G1: Trigger collect when free region count drops below threshold to prevent evacuation failures
• ... and 10 more: https://git.openjdk.java.net/jdk/compare/e663ba961f25c83758815bbfce97a58d9560c7a2...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[albertnetymk]

/contributor add pliden

[openjdk]

@albertnetymk
Contributor Per Liden <pliden@openjdk.org> successfully added.

[fisk]

Looks great!

[albertnetymk]

Thanks for the review.

/integrate

[openjdk]

@albertnetymk Since your change was applied there have been 42 commits pushed to the master branch:

• 4388959: 8268056: Update java.net and java.nio to use switch expressions
• 9cfd560: 8267663: [vector] Add unsigned comparison operators on AArch64
• 4413142: 8268017: C2: assert(phi_type->isa_int() || phi_type->isa_ptr() || phi_type->isa_long()) failed: bad phi type
• 2bfd708: 8266557: assert(SafepointMechanism::local_poll_armed(_handshakee)) failed: Must be
• 4d1cf51: 8240349: jlink should not leave partial image output directory on failure
• 07108c9: 8268241: deprecate JVM TI Heap functions 1.0
• c9dbc4f: 8266891: Provide a switch to force the class space to a specific location
• 2cc1977: 8268424: JFR tests fail due to GC cause 'G1 Preventive Collection' not in the valid causes after JDK-8257774
• 58a59e3: 8240997: Remove more "hack" word in security codes
• 1c3932f: 8264766: ClassCastException during template compilation (Variable cannot be cast to Param)
• ... and 32 more: https://git.openjdk.java.net/jdk/compare/e663ba961f25c83758815bbfce97a58d9560c7a2...master

Your commit was automatically rebased without conflicts.

Pushed as commit dd34a4c.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[mlbridge]

Mailing list message from charlie hunt on hotspot-gc-dev:

Nice to see this integrated. Great work!

charlie

On 6/9/21 5:40 AM, Albert Mingkun Yang wrote:

[mlbridge]

Mailing list message from charlie hunt on hotspot-gc-dev:

Nice to see this integrated. Great work!

charlie

On 6/9/21 5:40 AM, Albert Mingkun Yang wrote:

[albertnetymk]

Nice to see this integrated. Great work!

Thank you, and your help along the way is greatly appreciated.