8253237: [REDO] Improve large object handling during evacuation by kimbarrett · Pull Request #266 · openjdk/jdk

kimbarrett · 2020-09-19T17:03:05Z

Please review this change to improve the handling of arrays by G1's
copy_to_survivor_space.

This is essentially the same change that was pushed 9/15:
https://bugs.openjdk.java.net/browse/JDK-8158045
#90

and then backed out due to tripping over a compiler bug:
https://bugs.openjdk.java.net/browse/JDK-8253169
[BACKOUT] Improve large object handling during evacuation
#181

That compiler bug has been worked around:
https://bugs.openjdk.java.net/browse/JDK-8253270
Limit fastdebug inlining in G1 evacuation
#220

so now redoing the original change to array handling. The original
JDK-8158045 change was cherry-picked into this change. There were a couple of
minor merge conflicts with JDK-8253270.

The actual change (substantially cribbed from the old PR):

Change type dispatching and handling in G1's evacuation copying, in order to
improve the hot paths and improve array handling. This change addresses
several closely co-located enhancement requests; it seemed difficult to split
them up in a sensible way.

do_copy_to_survivor_space now gets the klass of the object being copied once,
up front, for use in multiple places. This avoids fetching (including
re-decoding when compressed) the klass several times. This addresses part of
JDK-8027545.

Moved check for and handling of string deduplication later, only applying it
after the special array cases have been dealt with, since strings are not
arrays. (They are header objects pointing to an array of character values.)

Special case typeArray, doing nothing other than the copy, since they contain
no oops that need to be processed. This addresses JDK-8027761.

Changed handling of objArray, possibly enqueuing multiple partial array tasks
for an array that is large enough. Initially no more than one partial array
task will be enqueued. As each such tasks is processed, an increasing number
of additional tasks may be enqueued, up to a limit based on the number of
worker threads. This gives other threads an opportunity to steal such tasks,
while keeping queue growth under control. Most of the calculation for this is
handled by a new helper class, so this can later be shared with ParallelGC.
This addresses JDK-8158045.

The dispatch on array klass type has also been changed. It will now break (via
an assert) Project Valhalla, rather than quietly doing something that probably
isn't what is actually wanted. I've discussed this with them so there is a
plan for dealing with it when they take this update.

Deleted a lingering reference to G1ParScanPartialArrayClosure that was deleted
long ago (JDK-8035330, JDK 9).

Ran tier1-6 in mach5 and some local stress tests.

I've not redone performance testing. I don't think there should be any change
from the previous go-round, which was pretty much performance neutral.

/issue 8253237, 8253238, 8253236
/label hotspot-gc
/summary Generate multiple partial array tasks for large objArrays.

Progress

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

Issues

JDK-8253237: [REDO] Improve large object handling during evacuation
JDK-8253238: [REDO] Improve object array chunking test in G1's copy_to_survivor_space
JDK-8253236: [REDO] Investigate fast-path for scanning only objects with references during gc

Reviewers

Stefan Johansson (@kstefanj - Reviewer)
Albert Mingkun Yang (@albertnetymk - Author)
Thomas Schatzl (@tschatzl - Reviewer)

Download

$ git fetch https://git.openjdk.java.net/jdk pull/266/head:pull/266
$ git checkout pull/266

8027761: Investigate fast-path for scanning only objects with references during gc 8027545: Improve object array chunking test in G1's copy_to_survivor_space Generate multiple partial array tasks for large objArrays. Reviewed-by: sjohanss, ayang, tschatzl

bridgekeeper · 2020-09-19T17:04:23Z

👋 Welcome back kbarrett! 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 · 2020-09-19T17:05:30Z

@kimbarrett This issue is referenced in the PR title - it will now be updated.

Adding additional issue to issue list: 8253238: [REDO] Improve object array chunking test in G1's copy_to_survivor_space.

Adding additional issue to issue list: 8253236: [REDO] Investigate fast-path for scanning only objects with references during gc.

openjdk · 2020-09-19T17:06:35Z

@kimbarrett
The hotspot-gc label was successfully added.

openjdk · 2020-09-19T17:07:02Z

@kimbarrett Setting summary to:

Generate multiple partial array tasks for large objArrays.
<!-- Anything below this marker will be automatically updated, please do not edit manually! -->
---------
### Progress
- [x] Change must not contain extraneous whitespace
- [x] Commit message must refer to an issue
- [ ] Change must be properly reviewed

### Issues
* [JDK-8253237](https://bugs.openjdk.java.net/browse/JDK-8253237): [REDO] Improve large object handling during evacuation
* [JDK-8253238](https://bugs.openjdk.java.net/browse/JDK-8253238): [REDO] Improve object array chunking test in G1's copy_to_survivor_space
* [JDK-8253236](https://bugs.openjdk.java.net/browse/JDK-8253236): [REDO] Investigate fast-path for scanning only objects with references during gc


### Download
`$ git fetch https://git.openjdk.java.net/jdk pull/266/head:pull/266`
`$ git checkout pull/266`

openjdk · 2020-09-19T17:07:47Z

@kimbarrett The following label will be automatically applied to this pull request: hotspot.

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 (add|remove) "label" command.

kimbarrett · 2020-09-19T17:08:07Z

/summary Generate multiple partial array tasks for large objArrays.

kimbarrett · 2020-09-19T17:08:22Z

/label remove hotspot

openjdk · 2020-09-19T17:08:47Z

@kimbarrett Updating existing summary to Generate multiple partial array tasks for large objArrays.

openjdk · 2020-09-19T17:09:16Z

@kimbarrett
The hotspot label was successfully removed.

mlbridge · 2020-09-19T17:16:48Z

Webrevs

00: Full (b895359)

kstefanj

Looked through the changes again and they still look good.

openjdk · 2020-09-21T07:30:45Z

@kimbarrett This change now passes all automated pre-integration checks. In addition to the automated checks, the change must also fulfill all project specific requirements

After integration, the commit message will be:

8253237: [REDO] Improve large object handling during evacuation
8253238: [REDO] Improve object array chunking test in G1's copy_to_survivor_space
8253236: [REDO] Investigate fast-path for scanning only objects with references during gc

Generate multiple partial array tasks for large objArrays.

Reviewed-by: sjohanss, ayang, tschatzl

If you would like to add a summary, use the /summary command.
To credit additional contributors, use the /contributor command.
To add additional solved issues, use the /issue command.

Since the source branch of this PR was last updated there have been 21 commits pushed to the master branch:

d1f9b8a: 8234808: jdb quoted option parsing broken
d8921ed: 8247281: migrate ObjectMonitor::_object to OopStorage
f800af9: 8241390: 'Deadlock' with VM_RedefineClasses::lock_classes()
2e30ff6: 8253311: Cleanup relocInfo constructors
43be5a3: 8230652: Improve verbose output
5a7390b: 8253418: ZGC: Use pd_ prefix to denote platform dependent code
7e49eae: 8253407: Move max_pow2 from test to src
fbfb62d: 8253332: ZGC: Make heap views reservation platform independent
dad6edb: 8253321: java.util.Locale.LanguageRange#equals is inconsistent after calling hashCode
edc14f9: 8253286: Use expand_exact() instead of expand_at() for fixed requests in G1
... and 11 more: https://git.openjdk.java.net/jdk/compare/224a30f12ce27257af94e2607c53e5f59ac2bd0f...master

As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid automatic rebasing, please merge master into your branch, and then specify the current head hash when integrating, like this: /integrate d1f9b8a8b54843f06a93078c4a058af86fcc2aac.

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

kimbarrett · 2020-09-22T05:12:45Z

Thanks for reviews, Stefan, Albert, and Thomas.

kimbarrett · 2020-09-22T05:13:19Z

/integrate

openjdk · 2020-09-22T05:14:26Z

@kimbarrett Since your change was applied there have been 21 commits pushed to the master branch:

d1f9b8a: 8234808: jdb quoted option parsing broken
d8921ed: 8247281: migrate ObjectMonitor::_object to OopStorage
f800af9: 8241390: 'Deadlock' with VM_RedefineClasses::lock_classes()
2e30ff6: 8253311: Cleanup relocInfo constructors
43be5a3: 8230652: Improve verbose output
5a7390b: 8253418: ZGC: Use pd_ prefix to denote platform dependent code
7e49eae: 8253407: Move max_pow2 from test to src
fbfb62d: 8253332: ZGC: Make heap views reservation platform independent
dad6edb: 8253321: java.util.Locale.LanguageRange#equals is inconsistent after calling hashCode
edc14f9: 8253286: Use expand_exact() instead of expand_at() for fixed requests in G1
... and 11 more: https://git.openjdk.java.net/jdk/compare/224a30f12ce27257af94e2607c53e5f59ac2bd0f...master

Your commit was automatically rebased without conflicts.

Pushed as commit 0e98fc1.

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

openjdk bot changed the title ~~8253237: [REDO] Improve large object handling during evacuation~~ 8253237: [REDO] Improve large object handling during evacuation Sep 19, 2020

openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Sep 19, 2020

openjdk bot added the hotspot hotspot-dev@openjdk.org label Sep 19, 2020

openjdk bot removed the hotspot hotspot-dev@openjdk.org label Sep 19, 2020

kimbarrett marked this pull request as ready for review September 19, 2020 17:12

openjdk bot added the rfr Pull request is ready for review label Sep 19, 2020

kstefanj approved these changes Sep 21, 2020

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openjdk bot added the ready Pull request is ready to be integrated label Sep 21, 2020

albertnetymk approved these changes Sep 21, 2020

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tschatzl approved these changes Sep 21, 2020

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openjdk bot closed this Sep 22, 2020

openjdk bot added integrated Pull request has been integrated and removed ready Pull request is ready to be integrated rfr Pull request is ready for review labels Sep 22, 2020

kimbarrett deleted the partial_arrays branch September 22, 2020 10:46

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