8271951: Consolidate preserved marks overflow stack in SerialGC #5022

rkennke · 2021-08-05T14:29:09Z

In SerialGC we put preserved marks in space that we may have in the young gen, and failing that, we push it to an overflow stack. The overflow stack is actually two stacks, and replicate behavior of the in-place preserved marks. These can be consolidated.

Testing:

tier1
tier2
hotspot_gc

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Issue

JDK-8271951: Consolidate preserved marks overflow stack in SerialGC

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Thomas Schatzl (@tschatzl - Reviewer) ⚠️ Review applies to fb48de4
Kim Barrett (@kimbarrett - Reviewer) ⚠️ Review applies to fb48de4

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bridgekeeper · 2021-08-05T14:30:26Z

👋 Welcome back rkennke! 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 · 2021-08-05T14:32:11Z

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

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mlbridge · 2021-08-05T14:36:43Z

Webrevs

01: Full - Incremental (c0f0d4ad)
00: Full (fb48de4d)

tschatzl

Lgtm.

Pre-existing, and just a side note and not directly aimed at you: when looking at the change, there is the PreservedMark class in Serial GC, and PreservedMarks with its OopAndMarkWord inner class and PreservedMarksSet in shared/preservedMarks.hpp which is not perfect naming. I'll probably file an RFE to look into this.

openjdk · 2021-08-09T09:48:03Z

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

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

8271951: Consolidate preserved marks overflow stack in SerialGC

Reviewed-by: tschatzl, kbarrett

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At the time when this comment was updated there had been 133 new commits pushed to the master branch:

ab41812: 8272576: G1: Use more accurate integer type for collection set length
82b2f21: 8272579: G1: remove unnecesary null check for G1ParScanThreadStateSet::_states slots
1c80f07: 8272334: com.sun.net.httpserver.HttpExchange: Improve API doc of getRequestHeaders
6d3d479: 8272667: substandard error messages from the docs build
73da66f: 8272318: Improve performance of HeapDumpAllTest
96107e3: 8272573: Redundant unique_concrete_method_4 dependencies
4d6593c: 8272124: Cgroup v1 initialization causes NullPointerException when cgroup path contains colon
30b0f82: 8272626: Avoid C-style array declarations in java.*
e8f1219: 8271276: C2: Wrong JVM state used for receiver null check
79a06df: 8272567: [IR Framework] Make AbstractInfo.getRandom() static
... and 123 more: https://git.openjdk.java.net/jdk/compare/685fc3c677cd0e71ef4443214ae14c7eed355140...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.

rkennke · 2021-08-09T10:31:54Z

Lgtm.

Pre-existing, and just a side note and not directly aimed at you: when looking at the change, there is the PreservedMark class in Serial GC, and PreservedMarks with its OopAndMarkWord inner class and PreservedMarksSet in shared/preservedMarks.hpp which is not perfect naming. I'll probably file an RFE to look into this.

We might even think about using PreservedMarksSet in Serial GC, if we can allocate it in free parts of the heap. Not sure how feasible that would be though...

tschatzl · 2021-08-09T12:47:35Z

Pre-existing, and just a side note and not directly aimed at you: when looking at the change, there is the PreservedMark class in Serial GC, and PreservedMarks with its OopAndMarkWord inner class and PreservedMarksSet in shared/preservedMarks.hpp which is not perfect naming. I'll probably file an RFE to look into this.

We might even think about using PreservedMarksSet in Serial GC, if we can allocate it in free parts of the heap. Not sure how feasible that would be though...

Agree. Filed JDK-8272147.

kimbarrett

Looks good. Just the question about PreservedMark::init.

kimbarrett · 2021-08-10T04:22:45Z

src/hotspot/share/gc/serial/markSweep.hpp

@@ -199,6 +198,8 @@ class PreservedMark {
  markWord _mark;

 public:
+  PreservedMark(oop obj, markWord mark) : _obj(obj), _mark(mark) {}
+
  void init(oop obj, markWord mark) {


Do we even need this init function anymore? Even if such an assignment is still needed, it could just use assignment from a newly constructed object, e.g. pm = PreservedMark(obj, mark);. The only place I found where it is used is preserve_marks, which can use the assignment form instead.

rkennke · 2021-08-19T19:50:13Z

/integrate

openjdk · 2021-08-19T19:51:44Z

Going to push as commit b40e8f0.
Since your change was applied there have been 137 commits pushed to the master branch:

7eccbd4: 8266519: Cleanup resolve() leftovers from BarrierSet et al
9569159: 8272674: Logging missing keytab file in Krb5LoginModule
51c1b9a: 8272616: Strange code in java.text.DecimalFormat#applyPattern
03b5e99: 8272165: Consolidate mark_must_be_preserved() variants
ab41812: 8272576: G1: Use more accurate integer type for collection set length
82b2f21: 8272579: G1: remove unnecesary null check for G1ParScanThreadStateSet::_states slots
1c80f07: 8272334: com.sun.net.httpserver.HttpExchange: Improve API doc of getRequestHeaders
6d3d479: 8272667: substandard error messages from the docs build
73da66f: 8272318: Improve performance of HeapDumpAllTest
96107e3: 8272573: Redundant unique_concrete_method_4 dependencies
... and 127 more: https://git.openjdk.java.net/jdk/compare/685fc3c677cd0e71ef4443214ae14c7eed355140...master

Your commit was automatically rebased without conflicts.

openjdk · 2021-08-19T19:51:56Z

@rkennke Pushed as commit b40e8f0.

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

8271951: Consolidate preserved marks overflow stack in SerialGC

fb48de4

openjdk bot added the rfr label Aug 5, 2021

openjdk bot added the hotspot-gc label Aug 5, 2021

tschatzl approved these changes Aug 9, 2021

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openjdk bot added the ready label Aug 9, 2021

kimbarrett approved these changes Aug 10, 2021

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Remove PreservedMark::init()

c0f0d4a

openjdk bot closed this Aug 19, 2021

openjdk bot added integrated and removed ready rfr labels Aug 19, 2021

8271951: Consolidate preserved marks overflow stack in SerialGC #5022

8271951: Consolidate preserved marks overflow stack in SerialGC #5022

rkennke commented Aug 5, 2021 •

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8271951: Consolidate preserved marks overflow stack in SerialGC #5022

8271951: Consolidate preserved marks overflow stack in SerialGC #5022

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rkennke commented Aug 5, 2021 • edited by openjdk[bot] bot

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