8283566: G1: Improve G1BarrierSet::enqueue performance #7921

shipilev · 2022-03-23T13:34:59Z

While looking at startup/warmup benchmarks for VarHandles, I noticed that G1BarrierSet::enqueue is not inlined and quite hot. Its uses also load the oop first, and then check if queues are active. This could be improved a bit. This only matters for the barrier paths that VM takes, which is the case for java.lang.invoke VM infra.

Not sure about enqueue_oop name, I did it to avoid accidental overload clash with enqueue(T* dst). Open for suggestions.

On a simple test:

import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;

public class VHWarmup {

    static final int SIZE = 1_000_000;

    private VarHandle[] vhs;
    private int x;

    public static void main(String... args) throws Exception {
        new VHWarmup().run();
    }

    public void run() throws Exception {
        vhs = new VarHandle[SIZE];
        for (int c = 0; c < SIZE; c++) {
            VarHandle vh = MethodHandles.lookup().findVarHandle(VHWarmup.class, "x", int.class);
            vh.get(this);
            vhs[c] = vh;
        }
    }
}

Baseline:

$ perf stat -r 10 build/linux-x86_64-server-release/images/jdk/bin/java -Xms128m -Xmx128m VHWarmup > /dev/null

 Performance counter stats for 'build/linux-x86_64-server-release/images/jdk/bin/java -Xms128m -Xmx128m VHWarmup' (10 runs):

          1,392.13 msec task-clock                #    1.183 CPUs utilized            ( +-  0.45% )
               887      context-switches          #    0.637 K/sec                    ( +-  1.05% )
                 6      cpu-migrations            #    0.004 K/sec                    ( +- 14.72% )
            31,755      page-faults               #    0.023 M/sec                    ( +-  0.17% )
     4,708,582,477      cycles                    #    3.382 GHz                      ( +-  0.44% )  (50.46%)
       168,230,638      stalled-cycles-frontend   #    3.57% frontend cycles idle     ( +-  2.75% )  (50.35%)
       790,033,580      stalled-cycles-backend    #   16.78% backend cycles idle      ( +-  1.82% )  (50.03%)
     9,094,235,238      instructions              #    1.93  insn per cycle         
                                                  #    0.09  stalled cycles per insn  ( +-  0.22% )  (49.54%)
     1,716,367,002      branches                  # 1232.909 M/sec                    ( +-  0.38% )  (49.65%)
         3,908,772      branch-misses             #    0.23% of all branches          ( +-  2.89% )  (49.97%)

           1.17642 +- 0.00616 seconds time elapsed  ( +-  0.52% )

Patched:

$ perf stat -r 10 build/linux-x86_64-server-release/images/jdk/bin/java -Xms128m -Xmx128m VHWarmup > /dev/null

 Performance counter stats for 'build/linux-x86_64-server-release/images/jdk/bin/java -Xms128m -Xmx128m VHWarmup' (10 runs):

          1,288.69 msec task-clock                #    1.203 CPUs utilized            ( +-  0.73% )
               860      context-switches          #    0.667 K/sec                    ( +-  1.38% )
                 7      cpu-migrations            #    0.006 K/sec                    ( +- 11.96% )
            31,830      page-faults               #    0.025 M/sec                    ( +-  0.13% )
     4,331,508,315      cycles                    #    3.361 GHz                      ( +-  0.72% )  (50.01%)
       151,638,797      stalled-cycles-frontend   #    3.50% frontend cycles idle     ( +-  2.94% )  (49.56%)
       604,797,159      stalled-cycles-backend    #   13.96% backend cycles idle      ( +-  4.17% )  (49.70%)
     8,517,580,297      instructions              #    1.97  insn per cycle         
                                                  #    0.07  stalled cycles per insn  ( +-  0.50% )  (49.99%)
     1,600,179,319      branches                  # 1241.714 M/sec                    ( +-  0.46% )  (50.44%)
         4,129,679      branch-misses             #    0.26% of all branches          ( +-  4.39% )  (50.30%)

           1.07125 +- 0.00822 seconds time elapsed  ( +-  0.77% )

Additional testing:

Linux x86_64 fastdebug tier1
Linux x86_64 fastdebug tier2
SPECjvm2008 shows no regressions

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Issue

JDK-8283566: G1: Improve G1BarrierSet::enqueue performance

Reviewers

Thomas Schatzl (@tschatzl - Reviewer)
Albert Mingkun Yang (@albertnetymk - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.java.net/jdk pull/7921/head:pull/7921
$ git checkout pull/7921

Update a local copy of the PR:
$ git checkout pull/7921
$ git pull https://git.openjdk.java.net/jdk pull/7921/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 7921

View PR using the GUI difftool:
$ git pr show -t 7921

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Download this PR as a diff file:
https://git.openjdk.java.net/jdk/pull/7921.diff

bridgekeeper · 2022-03-23T13:36:39Z

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openjdk · 2022-03-23T13:39:19Z

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

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mlbridge · 2022-03-23T13:42:55Z

Webrevs

tschatzl

Maybe rename enqueue_oop to enqueue_not_null? This is a fairly common naming scheme for methods specialized that way.

Lgtm.

openjdk · 2022-03-24T09:16:19Z

@shipilev 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:

8283566: G1: Improve G1BarrierSet::enqueue performance

Reviewed-by: tschatzl, 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 3 new commits pushed to the master branch:

720e751: 8283937: riscv: RVC: Fix c_beqz to c_bnez
51c05e8: 8282764: AArch64: compiler/vectorapi/reshape/TestVectorCastNeon.java failed with incorrect result
b82b009: 8283737: riscv: MacroAssembler::stop() should emit fixed-length instruction sequence

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shipilev · 2022-03-24T19:34:00Z

Maybe rename enqueue_oop to enqueue_not_null? This is a fairly common naming scheme for methods specialized that way.

Thing is, it is not about nullity. It is about whether we have already loaded the oop or not. Maybe enqueue_loaded?

tschatzl · 2022-03-25T09:11:55Z

Thing is, it is not about nullity. It is about whether we have already loaded the oop or not. Maybe enqueue_loaded?

Okay.

shipilev · 2022-03-28T11:00:01Z

Thing is, it is not about nullity. It is about whether we have already loaded the oop or not. Maybe enqueue_loaded?

Okay.

After some back and forth, I settled on enqueue_loc for new method. This matches some of the related methods we have in Shenandoah. This also simplifies the patch.

shipilev · 2022-03-30T07:42:35Z

Thing is, it is not about nullity. It is about whether we have already loaded the oop or not. Maybe enqueue_loaded?

Okay.

After some back and forth, I settled on enqueue_loc for new method. This matches some of the related methods we have in Shenandoah. This also simplifies the patch.

Any opinions about this version?

src/hotspot/share/gc/g1/g1BarrierSet.hpp

shipilev · 2022-03-31T17:47:07Z

Thanks for reviews!

/integrate

openjdk · 2022-03-31T17:49:20Z

Going to push as commit 6ebf845.
Since your change was applied there have been 38 commits pushed to the master branch:

d276da5: 8281469: aarch64: Improve interpreter stack banging
a41550b: 8283842: TestZoneTextPrinterParser.test_roundTripAtOverlap fails: DateTimeParseException
207b099: 8283890: Changes in CFG file format break C1Visualizer
49fcc7a: 8283013: Simplify Arguments::parse_argument()
73cb922: 8284026: Use unmodifiable collections where practical
77a205a: 8284090: com/sun/security/auth/module/AllPlatforms.java fails to compile
64025b0: 8283901: Introduce "make doctor" to diagnose build environment problems
5740a3b: 8280193: summary javadoc for java.awt.GraphicsEnvironment#preferProportionalFonts broken
a11cc97: 8283997: Unused argument in GraphKit::builtin_throw
067b258: 8224977: [macos] On AquaLookAndFeel, Iconified JInternalFrame does not restore when Control + F5 is used.
... and 28 more: https://git.openjdk.java.net/jdk/compare/edb42d7b0aabd07ef9f46cb1f0e862f7bb912378...master

Your commit was automatically rebased without conflicts.

openjdk · 2022-03-31T17:49:40Z

@shipilev Pushed as commit 6ebf845.

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

shipilev added 3 commits March 23, 2022 13:53

Inlining

f24cf37

More complete patch

0e6a534

Cleanups

76b5465

openjdk bot added the rfr Pull request is ready for review label Mar 23, 2022

openjdk bot added the hotspot-gc hotspot-gc-dev@openjdk.org label Mar 23, 2022

tschatzl approved these changes Mar 24, 2022

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openjdk bot added the ready Pull request is ready to be integrated label Mar 24, 2022

shipilev added 2 commits March 28, 2022 12:31

Merge branch 'master' into JDK-8283566-g1-enqueue

fcd7579

enqueue_loc

cdfd789

albertnetymk reviewed Mar 30, 2022

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src/hotspot/share/gc/g1/g1BarrierSet.hpp Outdated Show resolved Hide resolved

shipilev added 2 commits March 30, 2022 11:39

enqueue_preloaded*

b07308d

Merge branch 'master' into JDK-8283566-g1-enqueue

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tschatzl approved these changes Mar 30, 2022

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openjdk bot closed this Mar 31, 2022

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shipilev deleted the JDK-8283566-g1-enqueue branch April 6, 2022 08:45

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8283566: G1: Improve G1BarrierSet::enqueue performance #7921

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8283566: G1: Improve G1BarrierSet::enqueue performance #7921

8283566: G1: Improve G1BarrierSet::enqueue performance #7921

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