tools/metrics/histograms/histograms_xml/v8/histograms.xml

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<!--
This file is used to generate a comprehensive list of V8 histograms
along with a detailed description for each histogram.

For best practices on writing histogram descriptions, see
https://chromium.googlesource.com/chromium/src.git/+/HEAD/tools/metrics/histograms/README.md

Please send CLs to chromium-metrics-reviews@google.com rather than to specific
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-->

<histogram-configuration>

<histograms>

<histogram name="V8.ArrayBufferLargeAllocations" units="MB"
    expires_after="2021-06-07">
  <owner>gdeepti@chromium.org</owner>
  <owner>ecmziegler@chromium.org</owner>
  <summary>
    Number of bytes requested in array buffer allocations greater than one
    megabyte.
  </summary>
</histogram>

<histogram name="V8.ArrayBufferNewSizeFailures" units="MB"
    expires_after="2021-06-07">
  <owner>gdeepti@chromium.org</owner>
  <owner>ecmziegler@chromium.org</owner>
  <summary>Array buffer sizes for which V8 failed to allocate memory.</summary>
</histogram>

<histogram name="V8.CodeCacheRejectReason" enum="V8CodeCacheRejectReason"
    expires_after="M77">
  <owner>yangguo@chromium.org</owner>
  <summary>
    Reason code data has been rejected when attempting to deserialize.
  </summary>
</histogram>

<histogram name="V8.CodeCacheSizeRatio" units="%" expires_after="2021-04-18">
  <owner>yangguo@chromium.org</owner>
  <summary>Cache size to source size ratio when caching compiled code.</summary>
</histogram>

<histogram name="V8.CollectSourcePositions" units="microseconds"
    expires_after="M85">
  <owner>delphick@chromium.org</owner>
  <summary>
    Time spent collecting source positions to generate stack traces.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileCacheableMicroSeconds" units="microseconds"
    expires_after="M85">
  <owner>yangguo@chromium.org</owner>
  <summary>
    Time spent compiling a script that may be subject to caching.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileDeserializeMicroSeconds" units="microseconds"
    expires_after="2021-06-20">
  <owner>vogelheim@chromium.org</owner>
  <summary>
    Time spent deseriailzing code, used by V8 code caching.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileEvalMicroSeconds" units="microseconds"
    expires_after="M77">
  <owner>yangguo@chromium.org</owner>
  <summary>
    Time spent in V8 compiler (full codegen) for eval.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileLazyMicroSeconds" units="microseconds"
    expires_after="2021-06-13">
  <owner>hablich@chromium.org</owner>
  <summary>
    Aggregated time spent compiling functions lazily during a single script
    execution.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileMicroSeconds" units="microseconds"
    expires_after="2021-07-04">
  <owner>yangguo@chromium.org</owner>
  <summary>
    Time spent in V8 compiler (full codegen) excluding parser.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScript.CacheBehaviour" enum="V8CacheBehaviour"
    expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    The cache behaviour of compiling a V8 script, including whether we produced
    or consumed a code cache, whether we hit V8's isolate's cache, and if we
    didn't use the code cache, the reason why not.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds" units="microseconds"
    expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing/caching).

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.BackgroundThread"
    units="microseconds" expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>rmcilroy@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) on a background
    thread.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.ConsumeCache"
    units="microseconds" expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script when the 'compilation' is
    deserializing it from the code cache.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.ConsumeCache.Failed"
    units="microseconds" expires_after="2021-02-01">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing/caching) when the
    compilation tried to deserialize it from the code cache, but failed.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.IsolateCacheHit"
    units="microseconds" expires_after="2021-04-04">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing/caching) in the case
    where the V8 isolate's compilation cache is hit.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.NoCache.CacheTooCold"
    units="microseconds" expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) when the cache is too
    cold to use.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.NoCache.InlineScript"
    units="microseconds" expires_after="2021-02-01">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) when the script is an
    inline script.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.NoCache.Other"
    units="microseconds" expires_after="2021-02-01">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) when we do not want
    to cache it.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.NoCache.ScriptTooSmall"
    units="microseconds" expires_after="2021-06-13">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) when the script is
    too small to be cached.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.ProduceCache"
    units="microseconds" expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in compiling a script (incl. parsing) and serializing it
    for the code cache.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileScriptMicroSeconds.StreamingFinalization"
    units="microseconds" expires_after="2021-06-06">
  <owner>leszeks@chromium.org</owner>
  <owner>v8-runtime@google.com</owner>
  <summary>
    Total time spent in finalizing a script that was streaming compiled.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.CompileSerializeMicroSeconds" units="microseconds"
    expires_after="M77">
  <owner>vogelheim@chromium.org</owner>
  <summary>
    Time spent serializing code, used by V8 code caching.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.DebugFeatureUsage" enum="V8DebugFeature"
    expires_after="2022-01-10">
  <owner>yangguo@chromium.org</owner>
  <owner>bmeurer@chromium.org</owner>
  <summary>
    Debugger feature used at least once per isolate, recorded on first use.
  </summary>
</histogram>

<histogram name="V8.ErrorsThrownPerContext" units="errors"
    expires_after="2020-02-23">
  <owner>hablich@chromium.org</owner>
  <summary>
    The amount of JavaScript errors thrown by V8 per context. It does not count
    custom errors and ignores catched errors thrown by V8. This is collected
    after the context is detached.
  </summary>
</histogram>

<histogram name="V8.Execute" units="ms" expires_after="2021-05-09">
  <owner>rmcilroy@chromium.org</owner>
  <summary>
    Time spent in JavaScript Execution, including runtime calls, callbacks, and
    lazy compilation.
  </summary>
</histogram>

<histogram name="V8.GCBackgroundMarking" units="ms" expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in background tasks doing marking in one GC cycle. It is recorded
    after each GC.
  </summary>
</histogram>

<histogram name="V8.GCBackgroundScavenger" units="ms"
    expires_after="2021-06-13">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in background tasks doing scavenging in one GC cycle. It is
    recorded after each GC.
  </summary>
</histogram>

<histogram name="V8.GCBackgroundSweeping" units="ms" expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in background tasks doing sweeping in one GC cycle. It is
    recorded after each GC.
  </summary>
</histogram>

<histogram name="V8.GCCompactor" units="ms" expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent in mark-sweep phase of GC.</summary>
</histogram>

<histogram name="V8.GCCompactorBackground" units="ms"
    expires_after="2021-04-01">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in mark-sweep phase of GC in a background isolate.
  </summary>
</histogram>

<histogram name="V8.GCCompactorForeground" units="ms"
    expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in mark-sweep phase of GC in a foreground isolate.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC" units="ms" expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental latency-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Clear" units="ms" expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the clearing phase of incremental latency-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Epilogue" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the epilogue of incremental latency-optimized Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Evacuate" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the evacuation phase of incremental latency-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Finish" units="ms" expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the finish phase of incremental latency-optimized Mark-Compact
    GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Mark" units="ms" expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the marking phase of incremental latency-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Prologue" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the prologue of incremental latency-optimized Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMC.Sweep" units="ms" expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the sweeping phase of incremental latency-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMCBackground" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental latency-optimized
    Mark-Compact GC in a background isolate.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMCForeground" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental latency-optimized
    Mark-Compact GC in a foreground isolate.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMCReduceMemory" units="ms"
    expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental memory-optimized
    Mark-Compact GC.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMCReduceMemoryBackground" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental memory-optimized
    Mark-Compact GC in a background isolate.
  </summary>
</histogram>

<histogram name="V8.GCFinalizeMCReduceMemoryForeground" units="ms"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in the final atomic pause of incremental memory-optimized
    Mark-Compact GC in a foreground isolate.
  </summary>
</histogram>

<histogram name="V8.GCIncrementalMarking" units="ms" expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent doing incremental marking steps during GC.</summary>
</histogram>

<histogram name="V8.GCIncrementalMarkingFinalize" units="ms"
    expires_after="2021-04-01">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent in finalizing incremental marking.</summary>
</histogram>

<histogram name="V8.GCIncrementalMarkingReason" enum="GarbageCollectionReason"
    expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Reason an incremental marking was started in V8.</summary>
</histogram>

<histogram name="V8.GCIncrementalMarkingStart" units="ms"
    expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent in starting incremental marking.</summary>
</histogram>

<histogram name="V8.GCIncrementalMarkingSum" units="ms"
    expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    The total time spent in incremental marking steps in one GC cycle. It is
    only recorded if the time is non-zero.
  </summary>
</histogram>

<histogram name="V8.GCMainThreadMarkingThroughput" units="MB/s"
    expires_after="2021-04-01">
  <owner>mlippautz@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Marking throughput considering all durations of all marking phases on the
    main thread and marked bytes within one V8 garbage collection cycle.
    Reported once per garbage collection cycle. Only reported for platforms
    supporting high resolution clocks and when more than 1MB of live objects
    have been found.
  </summary>
</histogram>

<histogram name="V8.GCMarkCompactor" units="ms" expires_after="2021-06-27">
  <owner>mlippautz@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Sum of all durations of individual phases within one V8 mark-compact garbage
    collection. Reported once per garbage collection.
  </summary>
</histogram>

<histogram name="V8.GCMarkCompactReason" enum="GarbageCollectionReason"
    expires_after="2021-06-06">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Reason a mark-compact garbage collection was started in V8.</summary>
</histogram>

<histogram name="V8.GCMarkingSum" units="ms" expires_after="2021-06-06">
  <owner>mlippautz@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Sum of all durations of all marking phases (incremental and non-incremental)
    within one V8 garbage collection cycle. Reported once per garbage collection
    at the end.
  </summary>
</histogram>

<histogram name="V8.GCScavenger" units="ms" expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent in scavenging phase of GC.</summary>
</histogram>

<histogram name="V8.GCScavenger.ScavengeMain" units="ms"
    expires_after="2021-06-06">
  <owner>mlippautz@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Wall time spent in the main scavenging phase that copies over all reachable
    objects during a V8 scavenge.
  </summary>
</histogram>

<histogram name="V8.GCScavenger.ScavengeRoots" units="ms"
    expires_after="2021-04-01">
  <owner>mlippautz@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Time spent in scavenging the roots during a V8 scavenge.</summary>
</histogram>

<histogram name="V8.GCScavengerBackground" units="ms"
    expires_after="2021-06-13">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in scavenging phase of GC in a background isolate.
  </summary>
</histogram>

<histogram name="V8.GCScavengeReason" enum="GarbageCollectionReason"
    expires_after="2021-04-01">
  <owner>ulan@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>Reason a scavenge garbage collection was started in V8.</summary>
</histogram>

<histogram name="V8.GCScavengerForeground" units="ms"
    expires_after="2021-06-06">
  <owner>hpayer@chromium.org</owner>
  <owner>v8-memory-sheriffs@google.com</owner>
  <summary>
    Time spent in scavenging phase of GC in a foreground isolate.
  </summary>
</histogram>

<histogram name="V8.Initializer.LoadV8Snapshot.Result"
    enum="V8InitializerLoadV8SnapshotResult" expires_after="M77">
  <owner>oth@chromium.org</owner>
  <summary>Results from snapshot loading.</summary>
</histogram>

<histogram name="V8.Initializer.OpenV8File.Result"
    enum="V8InitializerOpenV8FileResult" expires_after="2020-05-10">
  <owner>oth@chromium.org</owner>
  <summary>Results from opening V8 snapshot files.</summary>
</histogram>

<histogram name="V8.LiftoffBailoutReasons" enum="LiftoffBailoutReason"
    expires_after="2021-06-13">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Liftoff (V8's baseline compiler for WebAssembly) bails out if it hits the
    first unsupported feature in a function. The function is recompiled with
    TurboFan then. This histogram records the bailout reason (or success) per
    WebAssembly function compilation in Liftoff.
  </summary>
</histogram>

<histogram name="V8.MemoryExternalFragmentationCodeSpace" units="%"
    expires_after="2020-03-01">
  <owner>hpayer@chromium.org</owner>
  <summary>
    External memory fragmentation in the code space after each GC in percent.
  </summary>
</histogram>

<histogram name="V8.MemoryExternalFragmentationLoSpace" units="%"
    expires_after="2020-06-01">
  <owner>hpayer@chromium.org</owner>
  <summary>
    External memory fragmentation in the large object space after each GC in
    percent.
  </summary>
</histogram>

<histogram name="V8.MemoryExternalFragmentationMapSpace" units="%"
    expires_after="2020-02-23">
  <owner>hpayer@chromium.org</owner>
  <summary>
    External memory fragmentation in the map space after each GC in percent.
  </summary>
</histogram>

<histogram name="V8.MemoryExternalFragmentationOldSpace" units="%"
    expires_after="2020-03-01">
  <owner>hpayer@chromium.org</owner>
  <summary>
    External memory fragmentation in the old space after each GC in percent.
  </summary>
</histogram>

<histogram name="V8.MemoryExternalFragmentationTotal" units="%"
    expires_after="M81">
  <owner>hpayer@chromium.org</owner>
  <summary>
    Total external memory fragmentation after each GC in percent.
  </summary>
</histogram>

<histogram name="V8.MemoryHeapSampleCodeSpaceCommitted" units="KB"
    expires_after="M77">
  <owner>hpayer@chromium.org</owner>
  <summary>
    The size of committed memory in the code space after each GC in KB.
  </summary>
</histogram>

<histogram name="V8.MemoryHeapSampleMapSpaceCommitted" units="KB"
    expires_after="2020-03-01">
  <owner>hpayer@chromium.org</owner>
  <summary>
    The size of committed memory in the map space after each GC in KB.
  </summary>
</histogram>

<histogram name="V8.MemoryHeapSampleMaximumCommitted" units="KB"
    expires_after="M77">
  <owner>hpayer@chromium.org</owner>
  <summary>
    The maximum size of committed memory used by V8 after each GC in KB.
  </summary>
</histogram>

<histogram name="V8.MemoryHeapSampleTotalCommitted" units="KB"
    expires_after="2021-07-04">
  <owner>hpayer@chromium.org</owner>
  <summary>
    The total size of committed memory used by V8 after each GC in KB.
  </summary>
</histogram>

<histogram name="V8.MemoryHeapSampleTotalUsed" units="KB"
    expires_after="2021-05-09">
  <owner>hpayer@chromium.org</owner>
  <summary>
    The total size of live memory used by V8 after each GC in KB.
  </summary>
</histogram>

<histogram name="V8.RegExpBacktracks" units="backtracks"
    expires_after="2021-06-06">
  <owner>jgruber@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    The number of backtracks performed in a single regexp execution.
  </summary>
</histogram>

<histogram name="V8.SharedArrayAllocationSizes" units="MB"
    expires_after="2020-12-02">
  <owner>gdeepti@chromium.org</owner>
  <owner>ulan@chromium.org</owner>
  <summary>
    Number of megabytes requested in shared array buffer allocations.
  </summary>
</histogram>

<histogram name="V8.StopTheWorld" units="ms" expires_after="2021-10-01">
  <owner>dinfuehr@chromium.org</owner>
  <owner>ulan@chromium.org</owner>
  <summary>Time spent in stopping other threads before performing GC.</summary>
</histogram>

<histogram name="V8.TimeToCollection" units="ms" expires_after="2021-10-01">
  <owner>dinfuehr@chromium.org</owner>
  <owner>ulan@chromium.org</owner>
  <summary>
    Time between requesting GC from background thread and actually starting
    collection on main thread.
  </summary>
</histogram>

<histogram name="V8.TurboFan1KTicks" units="1000 ticks"
    expires_after="2020-01-23">
  <owner>tebbi@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Number of ticks (in 1000s of ticks) from starting optimizing to installing
    the code object. Recorded on each regular optimization of a function.

    Similar to V8.TurboFanOptimizeTotalTime, but instead of counting time, we
    count a deterministic number of ticks sprinkled throughout the Turbofan
    compiler.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeConcurrentTotalTime" units="microseconds"
    expires_after="2021-05-16">
  <owner>bmeurer@chromium.org</owner>
  <owner>mslekova@chromium.org</owner>
  <summary>
    Total time from starting optimizing to installing the code object. Recorded
    on each regular, concurrent optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeExecute" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the execution phase of TurboFan optimization. Recorded on each
    regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeFinalize" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the finalization phase of TurboFan optimization. Recorded on
    each regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeForOnStackReplacementExecute"
    units="microseconds" expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the execution phase of TurboFan optimization for On Stack
    Replacement (OSR). Recorded on each optimization for on-stack replacement of
    a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeForOnStackReplacementFinalize"
    units="microseconds" expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the finalization phase of TurboFan optimization for On Stack
    Replacement (OSR). Recorded on each optimization for on-stack replacement of
    a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeForOnStackReplacementPrepare"
    units="microseconds" expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the preparation phase of TurboFan optimization for On Stack
    Replacement (OSR). Recorded on each optimization for on-stack replacement of
    a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeForOnStackReplacementTotalTime"
    units="microseconds" expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Total time from starting optimizing for On Stack Replacement (OSR) to
    installing the code object. Recorded on each optimization for on-stack
    replacement of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeNonConcurrentTotalTime"
    units="microseconds" expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <owner>mslekova@chromium.org</owner>
  <summary>
    Total time from starting optimizing to installing the code object. Recorded
    on each regular, non-concurrent optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizePrepare" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Time spent in the preparation phase of TurboFan optimization. Recorded on
    each regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeTotalBackground" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Total time spent on a background thread during TurboFan optimization.
    Recorded on each regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeTotalForeground" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Total time spent on the main thread during TurboFan optimization. Recorded
    on each regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.TurboFanOptimizeTotalTime" units="microseconds"
    expires_after="2021-05-09">
  <owner>neis@chromium.org</owner>
  <owner>mvstanton@chromium.org</owner>
  <summary>
    Total time from starting optimizing to installing the code object. Recorded
    on each regular optimization of a function.

    This histogram only records metrics on machines with high-resolution clocks.
  </summary>
</histogram>

<histogram name="V8.WasmAddressSpaceUsageMiB" units="MB"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>ahaas@chromium.org</owner>
  <summary>
    The total amount of address space reserved by the backing stores of all live
    WebAssembly.Memory backing stores in MiB. Recorded on each memory
    reservation.
  </summary>
</histogram>

<histogram name="V8.WasmCompileFunctionMicroSeconds" units="microseconds"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to compile a WebAssembly function. Recorded on each compilation of a
    single function, either synchronous, asynchronous, or lazily.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.WasmCompileFunctionPeakMemoryBytes" units="bytes"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Peak memory used to compile a WebAssembly function. Recorded for each
    TurboFan compilation of a WebAssembly function.
  </summary>
</histogram>

<histogram name="V8.WasmCompileModuleAsyncMicroSeconds" units="microseconds"
    expires_after="2021-07-04">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to asynchronously compile a WebAssembly module (using the
    'WebAssembly.compile' API). Recorded on each asynchronous WebAssembly
    compilation, but only if a high-resolution clock is available.
  </summary>
</histogram>

<histogram name="V8.WasmCompileModuleMicroSeconds" units="microseconds"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to compile a WebAssembly module. Recorded on each synchronous
    WebAssembly compilation.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.WasmCompileModuleStreamingMicroSeconds"
    units="microseconds" expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to asynchronously compile a WebAssembly module using streaming
    compilation (via the 'WebAssembly.compileStreaming' API). Recorded on each
    streaming WebAssembly compilation, but only if a high-resolution clock is
    available. Note that compilation speed is often limited by the network
    speed, which is also reflected in this metric.
  </summary>
</histogram>

<histogram name="V8.WasmFinishModuleStreamingMicroSeconds" units="microseconds"
    expires_after="2021-05-30">
  <owner>bbudge@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <summary>
    Time to asynchronously compile or deserialize a WebAssembly module during
    streaming compilation (via the 'WebAssembly.compileStreaming' API). Recorded
    on each streaming WebAssembly compilation or deserialization from the cache,
    but only if a high-resolution clock is available. Note that compilation
    speed is often limited by the network speed, which is also reflected in this
    metric.
  </summary>
</histogram>

<histogram name="V8.WasmFunctionSizeBytes" units="bytes"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Size of a WebAssembly function in bytes. Recorded on each compilation of a
    single function, either synchronous, asynchronous, or lazily.
  </summary>
</histogram>

<histogram name="V8.WasmFunctionsPerModule" units="functions"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Function count per WebAssembly module. Recorded for each WebAssembly module
    which is decoded for validation, compilation, or deserialization.
  </summary>
</histogram>

<histogram name="V8.WasmInstantiateModuleMicroSeconds" units="microseconds"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to instantiate a WebAssembly module. Recorded on each instantiation of
    a WebAssembly module.

    Warning: This metric may include reports from clients with low-resolution
    clocks (i.e. on Windows, ref. |TimeTicks::IsHighResolution()|). Such reports
    will cause this metric to have an abnormal distribution. When considering
    revising this histogram, see UMA_HISTOGRAM_CUSTOM_MICROSECONDS_TIMES for the
    solution.
  </summary>
</histogram>

<histogram name="V8.WasmMaxMemPagesCount" units="pages"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>ahaas@chromium.org</owner>
  <summary>
    Number of 64KiB pages a WebAssembly module declares as its maximum
    requirement. Recorded on each instantiation of a WebAssembly module.
  </summary>
</histogram>

<histogram name="V8.WasmMemoryAllocationResult" enum="WasmAllocationResult"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>ahaas@chromium.org</owner>
  <summary>
    The result of attempts to allocate WebAssembly.Memory buffers. Recorded on
    each attempt to allocate a WebAssembly.Memory buffer.
  </summary>
</histogram>

<histogram name="V8.WasmMinMemPagesCount" units="pages"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>ahaas@chromium.org</owner>
  <summary>
    Number of 64KiB pages a WebAssembly module declares as its minimum
    requirement. Recorded on each instantiation of a WebAssembly module.
  </summary>
</histogram>

<histogram name="V8.WasmModuleCodeSizeBaselineMiB" units="MB"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    The amount of generated code in MiB for one WebAssembly module. Recorded
    when baseline compilation finished.
  </summary>
</histogram>

<histogram name="V8.WasmModuleCodeSizeMiB" units="MB"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    The amount of committed code space in MiB used by individual WebAssembly
    modules. Recorded for each live module after each full GC.
  </summary>
</histogram>

<histogram name="V8.WasmModuleCodeSizePercentFreed" units="%"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    The percentage of WebAssembly code freed by garbage collection (ratio of
    total freed code to total generated code so far). Recorded for each live
    module after each full GC.
  </summary>
</histogram>

<histogram name="V8.WasmModuleCodeSizeTopTierMiB" units="MB"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    The amount of generated code in MiB for one WebAssembly module. Recorded
    when top-tier compilation finished.
  </summary>
</histogram>

<histogram name="V8.WasmModuleNumberOfCodeGCsTriggered" units="gcs"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Number of code GCs triggered per WebAssembly module. Recorded after each
    code GC.
  </summary>
</histogram>

<histogram name="V8.WasmModuleNumberOfCodeSpaces" units="spaces"
    expires_after="2021-03-31">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    The number of code spaces (i.e. individual reservations) of a WebAssembly
    module. Recorded on every code space allocation.
  </summary>
</histogram>

<histogram name="V8.WasmModuleSizeBytes" units="bytes"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>ahaas@chromium.org</owner>
  <summary>
    Size of the wire bytes of a WebAssembly module. Recorded for each
    WebAssembly module which is decoded for validation, compilation, or
    deserialization.
  </summary>
</histogram>

<histogram name="V8.WasmModulesPerEngine" units="count"
    expires_after="2021-05-30">
  <owner>clemensb@chromium.org</owner>
  <owner>ecmziegler@chromium.org</owner>
  <summary>
    Number of WebAssembly native modules live in a Wasm engine (typically per
    process). Recorded whenever a new native module is created.
  </summary>
</histogram>

<histogram name="V8.WasmModulesPerIsolate" units="count"
    expires_after="2021-05-30">
  <owner>clemensb@chromium.org</owner>
  <owner>ecmziegler@chromium.org</owner>
  <summary>
    Number of WebAssembly native modules live in an isolate. Recorded whenever a
    new native module is created.
  </summary>
</histogram>

<histogram name="V8.WasmTierUpModuleMicroSeconds" units="microseconds"
    expires_after="2021-05-30">
  <owner>ecmziegler@chromium.org</owner>
  <owner>adamk@chromium.org</owner>
  <owner>clemensb@chromium.org</owner>
  <summary>
    Time to tier-up a WebAssembly module, i.e. the time between baseline
    compilation finishes and top-tier compilation finishes. Recorded whenever an
    asynchronously compiled module finishes top-tier compilation, but only if a
    high-resolution clock is available.
  </summary>
</histogram>

</histograms>

</histogram-configuration>