February 2022 - hotspot-gc-dev

RFR: 8282089: [REDO] Parallel: Refactor PSCardTable::scavenge_contents_parallel
by Albert Mingkun Yang 01 Mar '22

01 Mar '22

Mostly the same as [JDK-8280783](https://bugs.openjdk.java.net/browse/JDK-8280783), except one assertion is weakened. assert(*dirty_r == clean_card || dirty_r >= clear_limit_r); Test: tier1-6 I also tried to reproduce the failures in https://bugs.openjdk.java.net/browse/JDK-8282062, but to no avail. ------------- Commit messages: - 8282089: [REDO] Parallel: Refactor PSCardTable::scavenge_contents_parallel" Changes: https://git.openjdk.java.net/jdk/pull/7573/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7573&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282089 Stats: 277 lines in 2 files changed: 103 ins; 101 del; 73 mod Patch: https://git.openjdk.java.net/jdk/pull/7573.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7573/head:pull/7573 PR: https://git.openjdk.java.net/jdk/pull/7573

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RFR: 8282307: Parallel: Incorrect discovery mode in PCReferenceProcessor
by Albert Mingkun Yang 24 Feb '22

24 Feb '22

Simple followup of [JDK-8273185](https://bugs.openjdk.java.net/browse/JDK-8273185). This bug should not affect correctness though: treating STW discovery as concurrent discovery. Test: hotspot_gc ------------- Commit messages: - ps-concurrent-discovery Changes: https://git.openjdk.java.net/jdk/pull/7590/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7590&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282307 Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/7590.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7590/head:pull/7590 PR: https://git.openjdk.java.net/jdk/pull/7590

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RFR: 8282348: Remove unused CardTable::dirty_card_iterate
by Albert Mingkun Yang 24 Feb '22

24 Feb '22

Simple change of removing dead code. Test: hotspot_gc ------------- Commit messages: - remove-dirty_card_iterate Changes: https://git.openjdk.java.net/jdk/pull/7610/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7610&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282348 Stats: 30 lines in 2 files changed: 0 ins; 30 del; 0 mod Patch: https://git.openjdk.java.net/jdk/pull/7610.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7610/head:pull/7610 PR: https://git.openjdk.java.net/jdk/pull/7610

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RFR: 8282299: Remove unused PartialArrayScanTask default constructor
by Albert Mingkun Yang 24 Feb '22

24 Feb '22

Trivial change of removing dead code. Test: build ------------- Commit messages: - trivial Changes: https://git.openjdk.java.net/jdk/pull/7588/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7588&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282299 Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod Patch: https://git.openjdk.java.net/jdk/pull/7588.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7588/head:pull/7588 PR: https://git.openjdk.java.net/jdk/pull/7588

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RFR: 8280958: G1/Parallel: Unify marking code structure
by Thomas Schatzl 22 Feb '22

22 Feb '22

Hi all, can I have reviews for this change that makes G1 and Parallel Full GC marking code structure a bit more similar both terms of structure as well as naming? This allows easier comparison and unless we are going to really merge them easier to do changes. They are still a bit different for several reasons: * G1 Full GC can disable class unloading while Parallel Full GC always unloads classes * different code structure in calls: Parallel GC drains the task queues after every kind of root, G1 only does at the end of all roots * root processing between the two collectors is very different All these are potential follow-ups. Thanks, Thomas ------------- Commit messages: - Initial change Changes: https://git.openjdk.java.net/jdk/pull/7561/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7561&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8280958 Stats: 43 lines in 6 files changed: 18 ins; 8 del; 17 mod Patch: https://git.openjdk.java.net/jdk/pull/7561.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7561/head:pull/7561 PR: https://git.openjdk.java.net/jdk/pull/7561

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RFR: 8282096: G1: Remove redundant checks in G1CardSet::free_mem_object
by Albert Mingkun Yang 21 Feb '22

21 Feb '22

Simple change of removing unnecessary checks. Test: hotspot_gc ------------- Commit messages: - g1-cardset Changes: https://git.openjdk.java.net/jdk/pull/7532/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7532&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282096 Stats: 9 lines in 1 file changed: 0 ins; 8 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/7532.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7532/head:pull/7532 PR: https://git.openjdk.java.net/jdk/pull/7532

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Integrated: 8282089: [BACKOUT] Parallel: Refactor PSCardTable::scavenge_contents_parallel
by Albert Mingkun Yang 18 Feb '22

18 Feb '22

Revert a commit to reduce tier1 noise while investigation. ------------- Commit messages: - Revert "8280783: Parallel: Refactor PSCardTable::scavenge_contents_parallel" Changes: https://git.openjdk.java.net/jdk/pull/7529/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7529&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282089 Stats: 277 lines in 2 files changed: 102 ins; 103 del; 72 mod Patch: https://git.openjdk.java.net/jdk/pull/7529.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7529/head:pull/7529 PR: https://git.openjdk.java.net/jdk/pull/7529

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RFR: 8282025: assert(ctrl != __null) failed: control out is assumed to be unique after JDK-8281732
by Jie Fu 17 Feb '22

17 Feb '22

Hi all, The following tests fail after JDK-8281732. compiler/gcbarriers/UnsafeIntrinsicsTest.java gc/metaspace/TestMetaspacePerfCounters.java gc/shenandoah/TestEvilSyncBug.java gc/stringdedup/TestStringDeduplicationFullGC.java gc/stringdedup/TestStringDeduplicationTableResize.java gc/stringdedup/TestStringDeduplicationYoungGC.java serviceability/dcmd/gc/HeapDumpCompressedTest.java jdk/jfr/event/gc/detailed/TestGCPhaseConcurrent.java jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionStateChangeEvent.java jdk/jfr/event/gc/detailed/TestShenandoahHeapRegionInformationEvent.java jdk/jfr/event/oldobject/TestShenandoah.java sun/net/www/protocol/https/HttpsURLConnection/B6216082.java sun/tools/jmap/BasicJMapTest.java ``` The fix just replaces `unique_ctrl_out()` with `unique_ctrl_out_or_null()`. Testing: - All failing tests passed after this patch Thanks. Best regards, Jie ------------- Commit messages: - 8282025: assert(ctrl != __null) failed: control out is assumed to be unique after JDK-8281732 Changes: https://git.openjdk.java.net/jdk/pull/7508/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7508&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8282025 Stats: 2 lines in 1 file changed: 1 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/7508.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7508/head:pull/7508 PR: https://git.openjdk.java.net/jdk/pull/7508

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RFR: 8281748: runtime/logging/RedefineClasses.java failed "assert(addr != __null) failed: invariant"
by Stefan Johansson 15 Feb '22

15 Feb '22

Please review this fix for [JDK-8281748](https://bugs.openjdk.java.net/browse/JDK-8281748). **Summary** In a recent [cleanup](https://bugs.openjdk.java.net/browse/JDK-8281637) a NULL-check in `G1CMIsAliveClosure::do_object_b(oop obj)` was forgotten. This was not caught by the initial testing because the only time the check is needed is when a referent is cleared **during** reference discovery, which is quite hard to trigger. The fix is fairly simple, but returning `true` when a `NULL` is passed in feels a bit counter-intuitive. This behavior is the same as prior to the cleanup causing the error and reading the code this will lead to not discovering references where the referent is `NULL`. **Testing** - [ ] Re-running mach5 tier1-5 ------------- Commit messages: - 8281748: runtime/logging/RedefineClasses.java failed "assert(addr != __null) failed: invariant" Changes: https://git.openjdk.java.net/jdk/pull/7476/files Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7476&range=00 Issue: https://bugs.openjdk.java.net/browse/JDK-8281748 Stats: 7 lines in 1 file changed: 6 ins; 0 del; 1 mod Patch: https://git.openjdk.java.net/jdk/pull/7476.diff Fetch: git fetch https://git.openjdk.java.net/jdk pull/7476/head:pull/7476 PR: https://git.openjdk.java.net/jdk/pull/7476

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Re: RFR: 8280088: NMT: Make mtGCCardSet the subcategory of mtGC
by Thomas Stuefe 15 Feb '22

15 Feb '22

On Mon, 17 Jan 2022 18:11:17 GMT, Aleksey Shipilev <shade(a)openjdk.org> wrote: > [JDK-8017163](https://bugs.openjdk.java.net/browse/JDK-8017163) introduced a new category, `mtGCCardSet` in NMT tracking. This makes logging look rather weird, and technically miscounts the space taken by GC-specific data structures, if you are accustomed to look at "GC" only: > > > - GC (reserved=142426KB, committed=142426KB) > (malloc=89554KB #3658) > (mmap: reserved=52872KB, committed=52872KB) > > - GCCardSet (reserved=128KB, committed=128KB) > (malloc=128KB #1539) > > > We can instead recast it as the subcategory of `mtGC`. It would be similar to `mtThreadStacks` that are accounted separately, but reported as part of `mtThread`. > > > - GC (reserved=142584KB, committed=142584KB) > (card sets: 128KB) > (malloc=89583KB #3780) > (mmap: reserved=52872KB, committed=52872KB) > > > Additional testing: > - [x] Linux x86_64 fastdebug `runtime/NMT` > - [ ] Linux x86_64 fastdebug `tier1` I created https://bugs.openjdk.java.net/browse/JDK-8281819 to track the proposed NMT category grouping ------------- PR: https://git.openjdk.java.net/jdk/pull/7115

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