8275056: Virtualize G1CardSet containers over heap region #6059

tschatzl · 2021-10-21T07:49:56Z

Hi all,

can I have reviews for this change that virtualizes G1CardSet "regions" over a heap region, allowing the use of multiple "G1CardSet card regions" across a single heap region?

I.e. HeapRegionRemSet, which is the interface to a region's card set, simply uses multiple indexes for the remembered set of a single source heap region if necessary. E.g. on a 128MB region, heap region 0's cards would be stored as (what I call) "card region" indexes 0..3 as appropriate in its _card_set.

When retrieving the values, the appropriate retransformation is done (during HeapRegionRemSet::iterate_for_merge()).

Assigning HeapRegionRemSet to handle all this multiplexing required some move of the G1CardSet::iterate_for_merge method to HeapRegionRemSet, which is why there are more changes than expected.

One change I would like to have opinions on is storing the amount of card regions per region into G1CardSetConfiguration, maybe it is better to put this into HeapRegionRemSet - but I did not want to start a HeapRegionRemSetConfiguration (maybe also put the cached values introduced in the split_card optimization there as well?).

This allows unlimited actual heap region size. Currently set to 512MB (what we would set ergonomically if on a 1 TB heap), but that's just a random number basically.
Feel free to suggest a different maximum heap region size if any. We could also keep the ergonomics use a smaller heap region size (e.g. 32M as before).

There is also a CSR to look at.

Testing: tier1-5, some perf testing on region sizes up to 512M with slight improvements in specjbb2015 with larger region sizes.

Thanks,
Thomas

Progress

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

Issue

JDK-8275056: Virtualize G1CardSet containers over heap region

Reviewers

Stefan Johansson (@kstefanj - Reviewer) ⚠️ Review applies to 216504d
Albert Mingkun Yang (@albertnetymk - Reviewer) ⚠️ Review applies to b644a84

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/6059/head:pull/6059
$ git checkout pull/6059

Update a local copy of the PR:
$ git checkout pull/6059
$ git pull https://git.openjdk.java.net/jdk pull/6059/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 6059

View PR using the GUI difftool:
$ git pr show -t 6059

Using diff file

Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/6059.diff

bridgekeeper · 2021-10-21T07:50:46Z

👋 Welcome back tschatzl! 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 · 2021-10-21T07:52:38Z

@tschatzl 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 · 2021-10-21T07:58:15Z

Webrevs

…test.

openjdk · 2021-10-25T21:49:45Z

@tschatzl this pull request can not be integrated into master due to one or more merge conflicts. To resolve these merge conflicts and update this pull request you can run the following commands in the local repository for your personal fork:

git checkout submit/8275056-virtualize-g1cardset-containers2
git fetch https://git.openjdk.java.net/jdk master
git merge FETCH_HEAD
# resolve conflicts and follow the instructions given by git merge
git commit -m "Merge master"
git push

kstefanj

Looks good, just a couple of small comments.

src/hotspot/share/gc/g1/g1CardSet.cpp

openjdk · 2021-10-27T10:10:54Z

@tschatzl 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:

8275056: Virtualize G1CardSet containers over heap region

Reviewed-by: sjohanss, ayang

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 78 new commits pushed to the master branch:

ca2efb7: 8274687: JDWP deadlocks if some Java thread reaches wait in blockOnDebuggerSuspend
296780c: 8276983: Small fixes to DumpAllocStat::print_stats
8c5f030: 8276453: Undefined behavior in C1 LIR_OprDesc causes SEGV in fastdebug build
176d21d: 8276824: refactor Thread::is_JavaThread_protected
74f3e69: 8277071: [BACKOUT] JDK-8276743 Make openjdk build Zip Archive generation "reproducible"
b85500e: 8276123: ZipFile::getEntry will not return a file entry when there is a directory entry of the same name within a Zip File
0d2980c: 8258192: Obsolete the CriticalJNINatives flag
5a2452c: 8274835: Remove unnecessary castings in java.base
3b2585c: 8276658: Clean up JNI local handles code
aeba653: 8276743: Make openjdk build Zip Archive generation "reproducible"
... and 68 more: https://git.openjdk.java.net/jdk/compare/ea23e7333e03abb4aca3e9f3854bab418a4b70e2...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.

…nfiguration, so move it to the correct constructor

tschatzl · 2021-10-27T12:07:56Z

Reran tier1-5 without issues (except assert problem that has been fixed in bdf9950).

tschatzl · 2021-10-28T12:49:47Z

After some discussion with @kstefanj we thought it would be best to limit the ergonomics to 32M regions (the previous maximum) since the choice of heap region size affects several other internal tuning (chunk sizing for scanning remembered sets, parallelism). Their impact has not been explored too much.

The user may still manually select larger sizes up to 512M at the moment, assuming that if you override the defaults, we assume that you will measure the impact appropriately. Of course, feedback by users about their choice is appreciated.

tschatzl · 2021-11-08T15:08:09Z

With the change for JDK-8276548 / PR#6230 now in (I merged it for your convenience), this change works now :) There has been no change in this PR, but the processing of "Full" cards has been wrong with region virtualization.

albertnetymk

Just some minor comments/suggestions.

albertnetymk · 2021-11-14T22:51:21Z

src/hotspot/share/gc/g1/heapRegionRemSet.inline.hpp

+  void do_cardsetptr(uint region_idx, size_t num_occupied, G1CardSet::CardSetPtr card_set) override {
+    CardOrRanges<Closure> cl(_iter,
+                             region_idx >> _log_card_regions_per_region,
+                             (region_idx & _card_regions_per_region_mask) << _log_card_region_size);
+    _card_set->iterate_cards_or_ranges_in_container(card_set, cl);


region_idx is actually card_region_idx, right? If so, card_region_idx >> _log_card_regions_per_region ==> region_idx (the second arg of G1ContainerCardsOrRanges constructor) makes sense to me.

Yes, that is the unchanged "region" that the hash table for the containers sees, which is the card_region_idx at this level.

albertnetymk · 2021-11-14T22:51:21Z

src/hotspot/share/gc/g1/g1CardSet.cpp

+                         (uint)HeapRegion::CardsPerRegion,                          /* max_cards_in_cardset */
+                         default_log2_card_region_per_region())                     /* log2_card_region_per_region */
+{
+  assert((_log2_card_region_per_heap_region + _log2_card_region_size) == (uint)HeapRegion::LogCardsPerRegion,


I suggest _log2_card_region_size -> _log2_cards_per_card_region; then the assertion becomes more consistent, IMO.
assert((_log2_card_region_per_heap_region + _log2_cards_per_card_region) == (uint)HeapRegion::LogCardsPerRegion), which, in math form, is
(card_region / heap_region) x (cards / card_region) == cards / (heap_)region

Implemented. I'll push in around 7-8 hours unless somebody objects.

tschatzl · 2021-11-15T18:08:13Z

Thanks @albertnetymk @kstefanj for your reviews.

/integrate

openjdk · 2021-11-15T18:09:40Z

Going to push as commit 1830b8d.
Since your change was applied there have been 85 commits pushed to the master branch:

fe45835: 8274856: Failing jpackage tests with fastdebug/release build
9046077: 8276084: Linux DEB Bundler: release number in outputted .deb file should be optional
7fc344d: 8277028: Use service type documentation as fallback for @provides
35a831d: 8272170: Missing memory barrier when checking active state for regions
02f7900: 8276932: G1: Annotate methods with override explicitly in g1CollectedHeap.hpp
fdcd16a: 8277048: Tiny improvements to the specification text for java.util.Properties.load
b231f5b: 8276921: G1: Remove redundant failed evacuation regions calculation in RemoveSelfForwardPtrHRClosure
ca2efb7: 8274687: JDWP deadlocks if some Java thread reaches wait in blockOnDebuggerSuspend
296780c: 8276983: Small fixes to DumpAllocStat::print_stats
8c5f030: 8276453: Undefined behavior in C1 LIR_OprDesc causes SEGV in fastdebug build
... and 75 more: https://git.openjdk.java.net/jdk/compare/ea23e7333e03abb4aca3e9f3854bab418a4b70e2...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-11-15T18:09:55Z

@tschatzl Pushed as commit 1830b8d.

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

Virtual heap regions in remembered sets

68f3fc2

openjdk bot added the rfr label Oct 21, 2021

openjdk bot added the hotspot-gc label Oct 21, 2021

32 bit compatibility - limit region size to 32M there as before. Fix …

216504d

…test.

openjdk bot added the merge-conflict label Oct 25, 2021

tschatzl changed the title ~~8275266: Virtualize G1CardSet containers over heap region~~ 8275056: Virtualize G1CardSet containers over heap region Oct 27, 2021

Merge branch 'master' into 8275056-virtualize-g1cardset-containers2

0167274

openjdk bot removed the merge-conflict label Oct 27, 2021

kstefanj approved these changes Oct 27, 2021

View changes

src/hotspot/share/gc/g1/g1CardSet.cpp Outdated Show resolved Hide resolved

src/hotspot/share/gc/g1/g1CardSet.cpp Outdated Show resolved Hide resolved

openjdk bot added the ready label Oct 27, 2021

tschatzl added 2 commits Oct 27, 2021

Fix assert after merge - the assert depends on current heap region co…

bdf9950

…nfiguration, so move it to the correct constructor

sjohanss review

df20ac6

Limit ergonomics to 32m regions

adf5f7b

tschatzl added 2 commits Oct 28, 2021

ayang review1

54a0358

Merge branch 'master' into 8275056-virtualize-g1cardset-containers2

b644a84

albertnetymk approved these changes Nov 14, 2021

View changes

tschatzl added 2 commits Nov 15, 2021

ayang review2

3b124f1

ayang review3

e0cfedd

openjdk bot closed this Nov 15, 2021

openjdk bot added the integrated label Nov 15, 2021

openjdk bot removed ready rfr labels Nov 15, 2021

tschatzl deleted the submit/8275056-virtualize-g1cardset-containers2 branch Nov 16, 2021

openjdk / jdk Public

8275056: Virtualize G1CardSet containers over heap region #6059

8275056: Virtualize G1CardSet containers over heap region #6059

tschatzl commented Oct 21, 2021 •

edited by openjdk[bot] bot

bridgekeeper bot commented Oct 21, 2021

openjdk bot commented Oct 21, 2021

mlbridge bot commented Oct 21, 2021 •

edited

openjdk bot commented Oct 25, 2021

kstefanj left a comment

openjdk bot commented Oct 27, 2021 •

edited

tschatzl commented Oct 27, 2021

tschatzl commented Oct 28, 2021

tschatzl commented Nov 8, 2021

albertnetymk left a comment

albertnetymk Nov 14, 2021

tschatzl Nov 15, 2021

albertnetymk Nov 14, 2021

tschatzl Nov 15, 2021

tschatzl commented Nov 15, 2021

openjdk bot commented Nov 15, 2021

openjdk bot commented Nov 15, 2021

openjdk / jdk Public

8275056: Virtualize G1CardSet containers over heap region #6059

8275056: Virtualize G1CardSet containers over heap region #6059

Conversation

tschatzl commented Oct 21, 2021 • edited by openjdk[bot] bot

Progress

Issue

Reviewers

Reviewing

bridgekeeper bot commented Oct 21, 2021

openjdk bot commented Oct 21, 2021

mlbridge bot commented Oct 21, 2021 • edited

Webrevs

openjdk bot commented Oct 25, 2021

kstefanj left a comment

openjdk bot commented Oct 27, 2021 • edited

tschatzl commented Oct 27, 2021

tschatzl commented Oct 28, 2021

tschatzl commented Nov 8, 2021

albertnetymk left a comment

albertnetymk Nov 14, 2021

Choose a reason for hiding this comment

tschatzl Nov 15, 2021

Choose a reason for hiding this comment

albertnetymk Nov 14, 2021

Choose a reason for hiding this comment

tschatzl Nov 15, 2021

Choose a reason for hiding this comment

tschatzl commented Nov 15, 2021

openjdk bot commented Nov 15, 2021

openjdk bot commented Nov 15, 2021

tschatzl commented Oct 21, 2021 •

edited by openjdk[bot] bot

mlbridge bot commented Oct 21, 2021 •

edited

openjdk bot commented Oct 27, 2021 •

edited