August 2019 - hotspot-gc-dev

RFR(T): 8230327: Make G1DirtyCardQueueSet free-id init unconditional
by Kim Barrett 30 Aug '19

30 Aug '19

Please review this trivial cleanup of G1DirtyCardQueueSet initialization. With the separation of G1RedirtyCardsQueueSet from G1DirtyCardQueueSet, the latter is now a singleton class that should always have an associated G1FreeIdSet. We can now unconditionally construct that object when constructing the DCQS. CR: https://bugs.openjdk.java.net/browse/JDK-8230327 Webrev: http://cr.openjdk.java.net/~kbarrett/8230327/open.00/ Testing: Local (linux-x64) hotspot:tier1.

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RFR(T): 8230372: Remove G1GCPhaseTimes::MergeLBProcessedBuffers
by Kim Barrett 30 Aug '19

30 Aug '19

Please review this trivial cleanup. We're removing a phase time work item that is no longer used for anything except logging. It is no longer interesting even for that, having been superseded by other, more useful information that is similarly logged. CR: https://bugs.openjdk.java.net/browse/JDK-8230372 Webrev: http://cr.openjdk.java.net/~kbarrett/8230372/open.00/ Testing: Local (linux-x64) hotspot:tier1. That includes gc/g1/TestGCLogMessages.java, which was checking for the associated

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RFR(S): 8227224: GenCollectedHeap: add subspace transitions for young gen for gc+heap=info log lines
by Tony Printezis 30 Aug '19

30 Aug '19

Hi all, Similar to 8227225 but for the GenCollectedHeap GCs. Webrev is here: http://cr.openjdk.java.net/~tonyp/8227224/webrev.0/ Tony ————— Tony Printezis | @TonyPrintezis | tprintezis(a)twitter.com

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RFR: 8230109: G1DirtyCardQueueSet should use card counts rather than buffer counts
by Kim Barrett 29 Aug '19

29 Aug '19

Please review this change to G1DirtyCardQueueSet and its clients to consistently use card counts, rather than a mix of card counts and buffer counts, to measure pending work and work performed. JDK-8227719 already changed DCQS to use card counts internally, but retained the buffer count API (estimating based on card counts and the buffer size) to reduce the fanout from that change. This change removes that buffer count API and updates clients to consistently use card counts. It also updates some names accordingly. For example, *log_buffer_entry* => *logged_cards*. There aren't any _intentional_ behavioral changes here, just unit and nomenclature changes. A lingering use of buffer counts is DCQS::_processed_buffers_(mut|rs_thread). These are only used in the RemSetSummary, to print some statistics. I'm planning to address that as part of other work. CR: https://bugs.openjdk.java.net/browse/JDK-8230109 Webrev: http://cr.openjdk.java.net/~kbarrett/8230109/open.00/ Testing: mach5 tier1-3 Manually examined log output for gcbasher to verify refinement related values were consistent with using card units rather than buffer units.

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RFR: JDK-8215166: Remove unused G1PretouchAuxiliaryMemory option
by Evgeny Mandrikov 29 Aug '19

29 Aug '19

Hello! Please review patch [1] for JDK-8215166 [2]. Also it needs a sponsor since I have only author status in OpenJDK Census [3]. After this change tier1 tests pass on my machine and I don't find other occurrences of "G1PretouchAuxiliaryMemory". With best regards, Evgeny Mandrikov [1] http://cr.openjdk.java.net/~godin/8215166/webrev.00/ [2] https://bugs.openjdk.java.net/browse/JDK-8215166 [3] https://openjdk.java.net/census#godin

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RFR(T): 8230332: G1DirtyCardQueueSet _notify_when_complete is always true
by Kim Barrett 29 Aug '19

29 Aug '19

Please review this trivial cleanup of G1DirtyCardQueueSet. With the separation of G1RedirtyCardsQueueSet from G1DirtyCardQueueSet, the latter is now a singleton class. As a result, the _notify_when_complete member (used to control whether adding completed buffers should notify the completed buffer monitor) is always true. This change removes that member and changes the conditional notifications to be unconditional. Also cleaned up some locker usage for _cbl_mon when notification is needed, and changed to consistently use notify_all() (there's no good reason to use notify(), and definitely no good reason to use a mix of the two here). CR: https://bugs.openjdk.java.net/browse/JDK-8230332 Webrev: http://cr.openjdk.java.net/~kbarrett/8230332/open.00/ Testing: Local (linux-x64) hotspot:tier1

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RFR(XS): 8229210: [TESTBUG] Move gc stress tests from JFR directory tree to gc/stress
by mikhailo.seledtsov＠oracle.com 29 Aug '19

29 Aug '19

Please review this change that simply moves GC+JFR stress tests from test/jdk/jdk/jfr/event/gc/detailed/TestStress* to test/hotspot/jtreg/gc/stress/jfr/ This change was originated by JFR team, and later informally discussed with GC team members. The goal is to remove heavy time-consuming GC event stress tests from JFR hierarchy to GC/stress, where they better fit. JBS: https://bugs.openjdk.java.net/browse/JDK-8229210 Webrev: http://cr.openjdk.java.net/~mseledtsov/8229210.00/ Just a simple move, no changes to the tests: hg mv test/jdk/jdk/jfr/event/gc/detailed/TestStress* test/hotspot/jtreg/gc/stress/jfr/ Testing: 1. Sanity: Ran test/hotspot/jtreg/gc/stress/jfr/ - PASS 2. Sanity: running jdk_jfr - in progress Thank you, Misha

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RFR: ZGC: Make zGlobals and zArguments OS agnostic
by Erik Österlund 29 Aug '19

29 Aug '19

Hi, The contents of zGlobals and zArguments are cpu-specific, but not os_cpu-specific. Therefore, these files should be moved to be cpu-specific only. Webrev: http://cr.openjdk.java.net/~eosterlund/8230307/webrev.00/ Bug: https://bugs.openjdk.java.net/browse/JDK-8230307 Thanks, /Erik

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RFR(S): 8230126: delay_to_keep_mmu can delay shutdown
by Kim Barrett 28 Aug '19

28 Aug '19

Please review this change to G1ConcurrentMarkThread::delay_to_keep_mmu to use a wait-with-timeout on CGC_lock rather than os::sleep to implement the delay. This allows the delay to be terminated early by a thread termination request. Also fixed a units bug in the calculation of the delay. The call to G1MMUTracker::when_ms was with "now" in seconds and "prediction" in milliseconds. This function expects both arguments to be in seconds, and returns a millisecond result. This bug was largely masked by the calculation first clipping the prediction value to the max GC time. CR: https://bugs.openjdk.java.net/browse/JDK-8230126 Webrev: http://cr.openjdk.java.net/~kbarrett/8230126/open.00/ Testing: mach5 tier1-3 Locally (linux-x64) ran gcbasher test with some additional logging added to the changed functions to verify the various values looked okay.

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RFR: 8229278: Improve hs_err location printing to assume less about GC internals
by Erik Österlund 28 Aug '19

28 Aug '19

Hi, Today when we crash and print hs_err files, the printing utility for describing heap locations assumes: 1) That the Java heap memory reservation is contiguous 2) That the Java heap is parseable We should let the GC describe a location instead, opting in to such concepts. This patch adds a print_location pure virtual function on CollectedHeap allowing the GC to choose printing strategy. A new LocationPrinter utility was added, allowing GCs to implement the functionality easily without much code duplication. Webrev: http://cr.openjdk.java.net/~eosterlund/8229278/webrev.00/ Bug: https://bugs.openjdk.java.net/browse/JDK-8229278 Thanks, /Erik

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