7903455: JMH: Add "mempool" profiler

[ericcaspole]

I started off to show only the code cache related size, but I don't see any reason to not print all the available mbean pool info. We often adapt app or library code to run as JMH, to use all its benefits. In those cases seeing the code cache stats is more interesting than say, for a regular JDK API JMH benchmark. I verified the CodeHeap stats match well with +PrintCodeCache. There is mbean pool data for all the GCs as well.

Example output:

Benchmark (iterations) Mode Cnt Score Error Units
SpillCode.testSpillForManyInts 10 avgt 5 705.433 ± 9.570 ns/op
SpillCode.testSpillForManyInts:·CodeHeap 'non-nmethods'.used 10 avgt 5 1139.000 kB
SpillCode.testSpillForManyInts:·CodeHeap 'non-profiled nmethods'.used 10 avgt 5 209.750 kB
SpillCode.testSpillForManyInts:·CodeHeap 'profiled nmethods'.used 10 avgt 5 924.875 kB
SpillCode.testSpillForManyInts:·Compressed Class Space.used 10 avgt 5 403.375 kB
SpillCode.testSpillForManyInts:·G1 Eden Space.used 10 avgt 5 8192.000 kB
SpillCode.testSpillForManyInts:·G1 Old Gen.used 10 avgt 5 8160.000 kB
SpillCode.testSpillForManyInts:·G1 Survivor Space.used 10 avgt 5 ≈ 0 kB
SpillCode.testSpillForManyInts:·Metaspace.used 10 avgt 5 3617.320 kB
SpillCode.testSpillForManyInts:·Total CodeHeap.used 10 avgt 5 2267.000 kB
SpillCode.testSpillForManyInts:·Total MemPools.used 10 avgt 5 22639.695 kB

---

Progress

• Change must not contain extraneous whitespace
• Change must be properly reviewed (1 review required, with at least 1 Committer)

Issue

• CODETOOLS-7903455: JMH: Add "mempool" profiler

Reviewers

• Aleksey Shipilev (@shipilev - Committer)

Reviewing

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[bridgekeeper]

👋 Welcome back ecaspole! 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.

[shipilev]

This looks useful!

I think the whole thing can be simpler, though:

public class MemPoolProfiler implements InternalProfiler {
    static final double BYTES_PER_KIB = 1024D;

    @Override
    public String getDescription() {
        return "Memory pool/footprint profiling via standard MBeans";
    }

    @Override
    public void beforeIteration(BenchmarkParams benchmarkParams, IterationParams iterationParams) {
        for (MemoryPoolMXBean b : ManagementFactory.getMemoryPoolMXBeans()) {
            b.resetPeakUsage();
        }
    }

    @Override
    public Collection<? extends Result> afterIteration(BenchmarkParams benchmarkParams, IterationParams iterationParams, IterationResult result) {
        List<Result> results = new ArrayList<>();

        long sumCodeHeap = 0L;
        long sum = 0L;
        for (MemoryPoolMXBean bean : ManagementFactory.getMemoryPoolMXBeans()) {
            long used = bean.getPeakUsage().getUsed();
            if (bean.getName().contains("CodeHeap")) {
                sumCodeHeap += used;
            }
            sum += used;

            results.add(new ScalarResult(Defaults.PREFIX + "mempool." + bean.getName() + ".used", used / BYTES_PER_KIB, "KiB", AggregationPolicy.MAX));
        }

        results.add(new ScalarResult(Defaults.PREFIX + "mempool.total.codeheap.used", sumCodeHeap / BYTES_PER_KIB, "KiB", AggregationPolicy.MAX));
        results.add(new ScalarResult(Defaults.PREFIX + "mempool.total.used", sum / BYTES_PER_KIB, "KiB", AggregationPolicy.MAX));
        return results;
    }
}

In addition to this version being more readable, it also does only a single pass through the beans, which means sums and individual metrics would always agree.

[shipilev]

Please also make sure to pass GHA tests: go to https://github.com/ericcaspole/jmh/actions and enable the workflows there.

[ericcaspole]

Thanks for your changes, it is better with your version.

[mlbridge]

Webrevs

• 01: Full - Incremental (72c014a2)
• 00: Full (01d175d7)

[shipilev]

Need a new line at the end of file.

[shipilev]

Looks good, feel free to push once GHA are clean.
(If we need something else from this profiler, we can do that separately)

[openjdk]

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

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

7903455: JMH: Add "mempool" profiler

Reviewed-by: shade

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

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[ericcaspole]

/integrate

[openjdk]

Going to push as commit 8716778.

[openjdk]

@ericcaspole Pushed as commit 8716778.

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