<!--
Copyright 2020 The Chromium Authors
Use of this source code is governed by a BSD-style license that can be
found in the LICENSE file.
-->

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

For best practices on writing histogram descriptions, see
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Please follow the instructions in the OWNERS file in this directory to find a
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<histogram-configuration>

<histograms>

<histogram name="DiskCache.0.AsyncIOTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time for an async IO operation to complete. This covers content Writes
    and Reads, measured from the cache thread.
  </summary>
</histogram>

<histogram name="DiskCache.0.AsyncReadDispatchTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The synchronous portion of an async read.</summary>
</histogram>

<histogram name="DiskCache.0.AsyncWriteDispatchTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The synchronous portion of an async write.</summary>
</histogram>

<histogram name="DiskCache.0.AverageOpenEntries2" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of open disk cache entries at any given time.
  </summary>
</histogram>

<histogram name="DiskCache.0.BufferBytes" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The total size of all the internal buffers.</summary>
</histogram>

<histogram name="DiskCache.0.ByteIORate" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of KB accessed from the cache in a 30 seconds interval.
  </summary>
</histogram>

<histogram name="DiskCache.0.CreateTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent creating a new entry on the cache.</summary>
</histogram>

<histogram name="DiskCache.0.DeletedAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The age of the last entry on the queue of deleted entries.</summary>
</histogram>

<histogram name="DiskCache.0.DeleteData" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The size of the data portion of a given entry by the time it is deleted.
  </summary>
</histogram>

<histogram name="DiskCache.0.DeletedRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The percentage of the deleted entries.</summary>
</histogram>

<histogram name="DiskCache.0.DeleteFailed" units="files" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>Number of external files that we were unable to delete.</summary>
</histogram>

<histogram name="DiskCache.0.DeleteHeader" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The size of the HTML headers of a given entry by the time it is deleted.
  </summary>
</histogram>

<histogram name="DiskCache.0.Entries" units="entries" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The number of entries currently stored on the cache.</summary>
</histogram>

<histogram name="DiskCache.0.EntriesFull" units="entries" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries currently stored on the cache, after it is full.
  </summary>
</histogram>

<histogram name="DiskCache.0.EntryAccessRate" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries accessed by the cache in a 30 seconds interval.
  </summary>
</histogram>

<histogram name="DiskCache.0.EntrySize" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average size of an entry. It is only measured after the cache is full,
    so evictions are taking place.
  </summary>
</histogram>

<histogram name="DiskCache.0.Error" enum="DiskCacheError"
    expires_after="2023-10-01">
  <owner>wfh@chromium.org</owner>
  <owner>src/net/disk_cache/OWNERS</owner>
  <summary>
    Critical error ids. Reported each time the disk backed blockfile cache
    encounters an error or a critical error. Warning: this histogram was expired
    from Oct 2020 to Sep 2021; data may be missing.
  </summary>
</histogram>

<histogram name="DiskCache.0.FillupAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The age of the cache (in hours) by the time we reach the size limit.
  </summary>
</histogram>

<histogram name="DiskCache.0.FillupTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of hours required to fill up the cache, as measured by the cache
    being running.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstByteIORate" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of KB accessed from the cache in a 30 seconds interval,
    by the time we reach the cache size limit.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstEntryAccessRate" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of entries accessed by the cache in a 30 seconds
    interval, by the time we reach the cache size limit.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstEntrySize" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average size of an entry by the time we reach the cache size limit.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstHighUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the entries that are highly reused, by the time we fill up
    the cache.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstHitRatio" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio by the time we fill up the cache. Of course, we started with
    an empty cache.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstLargeEntriesRatio" units="%"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the cache used by entries of more than 512 KB, by the time
    we reach the cache size limit.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstLowUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the entries that have been reused a few times, by the time
    we fill up the cache.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstNoUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the entries that have never been reused, by the time we
    fill up the cache.
  </summary>
</histogram>

<histogram name="DiskCache.0.FirstResurrectRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of re-created deleted entries versus entries that we really
    don't know about.
  </summary>
</histogram>

<histogram name="DiskCache.0.GetRankings" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent reading the LRU-related portion of an entry.</summary>
</histogram>

<histogram name="DiskCache.0.HighUseAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The age of the last entry on the queue of highly used entries.
  </summary>
</histogram>

<histogram name="DiskCache.0.HighUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The percentage of the entries that are highly reused.</summary>
</histogram>

<histogram name="DiskCache.0.HitRatio" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The current hit ratio. It is only measured after the cache is full, so
    evictions are taking place, and data from the fill-up period is not
    considered.
  </summary>
</histogram>

<histogram name="DiskCache.0.HitRatioBySize2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each size. To calculate the hit ratio of caches of a
    certain size, take the ratio of a bin in this histogram to the same bin in
    DiskCache.0.Size2.
  </summary>
</histogram>

<histogram name="DiskCache.0.HitRatioByTotalTime" units="hours"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each total time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.0.TotalTime.
  </summary>
</histogram>

<histogram name="DiskCache.0.HitRatioByUseTime" units="hours"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each use time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.0.UseTime.
  </summary>
</histogram>

<histogram name="DiskCache.0.IndexLoad" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Percentage of the index table that is currently used (the cache is full).
  </summary>
</histogram>

<histogram name="DiskCache.0.KeySize" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The size of each key.</summary>
</histogram>

<histogram name="DiskCache.0.LargeEntriesRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Percentage of the cache used by entries of more than 512 KB. It is only
    measured after the cache is full, so evictions are taking place.
  </summary>
</histogram>

<histogram name="DiskCache.0.LowUseAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The age of the last entry on the queue of entries reused a few times.
  </summary>
</histogram>

<histogram name="DiskCache.0.LowUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the entries that have been reused a few times.
  </summary>
</histogram>

<histogram name="DiskCache.0.MaxOpenEntries2" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The maximum number of simultaneously open disk cache entries.
  </summary>
</histogram>

<histogram name="DiskCache.0.MaxSize2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The maximum size of the cache.</summary>
</histogram>

<histogram name="DiskCache.0.NoUseAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The age of the next entry to be evicted that has never been reused.
  </summary>
</histogram>

<histogram name="DiskCache.0.NoUseRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The percentage of the entries that have never been reused.</summary>
</histogram>

<histogram name="DiskCache.0.NumberOfReferences" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of open entry references at any given moment.

    Closely related to AverageOpenEntries, but this one is not the average per
    client but instead a direct histogram updated every 30 secs.
  </summary>
</histogram>

<histogram name="DiskCache.0.OpenTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent opening an entry already on the cache (cache hit).
  </summary>
</histogram>

<histogram name="DiskCache.0.PendingIO" units="operations" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The number of pending IO operations (Async IO).</summary>
</histogram>

<histogram name="DiskCache.0.ReadTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent reading from an entry.</summary>
</histogram>

<histogram name="DiskCache.0.ResurrectRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of re-created deleted entries versus entries that we really
    don't know about.
  </summary>
</histogram>

<histogram name="DiskCache.0.ShortReport" enum="ShortReportReason"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The reason for not sending a full report.</summary>
</histogram>

<histogram name="DiskCache.0.Size2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The current size of the cache.</summary>
</histogram>

<histogram name="DiskCache.0.SparseReadTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent reading from an sparse entry.</summary>
</histogram>

<histogram name="DiskCache.0.SparseWriteTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent writing to an sparse entry.</summary>
</histogram>

<histogram name="DiskCache.0.TotalClearTimeV1" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent deleting the cache. (Clear browsing data).</summary>
</histogram>

<histogram name="DiskCache.0.TotalClearTimeV2" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent deleting the cache. (Clear browsing data).</summary>
</histogram>

<histogram name="DiskCache.0.TotalDoomCache" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of times that this cache has been deleted by the user.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalDoomRecentEntries" units="?"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of times that the user has deleted new entries from this cache.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalEvictionsGaJs" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The number of times that ga.js was evicted.</summary>
</histogram>

<histogram name="DiskCache.0.TotalFatalErrors" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of fatal errors detected for this cache (so we delete
    everything).
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalIOTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The total time it takes to perform a payload IO operation (AKA, directed to
    an entry). This is measured from the IO thread.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalIOTimeRead" units="ms"
    expires_after="2023-10-15">
  <owner>jam@chromium.org</owner>
  <owner>swarm-team@google.com</owner>
  <summary>
    The total time it takes to perform a read IO operation. This is emitted at
    each cache read, and measures from the IO thread to background thread,
    waiting for the disk read, and back to the IO thread.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalIOTimeWrite" units="ms"
    expires_after="2023-10-15">
  <owner>jam@chromium.org</owner>
  <owner>swarm-team@google.com</owner>
  <summary>
    The total time it takes to perform a write IO operation. This is emitted at
    each cache read, and measures from the IO thread to background thread,
    optionally waiting for the disk write, and back to the IO thread.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>Number of hours that the cache has been used.</summary>
</histogram>

<histogram name="DiskCache.0.TotalTimeNotFull" units="hours"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of hours that the cache has been in use, for users that still
    have available space.
  </summary>
</histogram>

<histogram name="DiskCache.0.TotalTrimDeletedTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent removing deleted entries from the cache.</summary>
</histogram>

<histogram name="DiskCache.0.TotalTrimTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent removing old entries from the cache.</summary>
</histogram>

<histogram name="DiskCache.0.TotalTrimTimeV1" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent removing old entries from the cache.</summary>
</histogram>

<histogram name="DiskCache.0.TotalTrimTimeV2" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent evicting entries from the cache (moving them to the deleted
    list).
  </summary>
</histogram>

<histogram name="DiskCache.0.TrimAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time that an entry lives in the cache without being accessed until it is
    finally purged.
  </summary>
</histogram>

<histogram name="DiskCache.0.TrimDeletedItems" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are deleted on a single iteration.
  </summary>
</histogram>

<histogram name="DiskCache.0.TrimItemsV1" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are evicted on a single iteration.
  </summary>
</histogram>

<histogram name="DiskCache.0.TrimItemsV2" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are evicted (moved to the deleted list) on a
    single iteration.
  </summary>
</histogram>

<histogram name="DiskCache.0.TrimRate" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The number of entries that are evicted per hour of use.</summary>
</histogram>

<histogram name="DiskCache.0.UpdateRank" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent moving an entry to the front of the LRU list.
  </summary>
</histogram>

<histogram name="DiskCache.0.UsedSpace" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the allowed disk space that we are currently using.
  </summary>
</histogram>

<histogram name="DiskCache.0.UseTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Number of hours that the cache has been used since last week.
  </summary>
</histogram>

<histogram name="DiskCache.0.WriteTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent writing to an entry.</summary>
</histogram>

<histogram name="DiskCache.2.AsyncIOTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time for an async IO operation to complete. This covers content Writes
    and Reads, measured from the cache thread. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.AsyncReadDispatchTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The synchronous portion of an async read. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.AsyncWriteDispatchTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The synchronous portion of an async write. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.AverageOpenEntries2" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of open disk cache entries at any given time.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.BufferBytes" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The total size of all the internal buffers. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.ByteIORate" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of KB accessed from the cache in a 30 seconds interval.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.CreateTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent creating a new entry on the cache. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.DeleteData" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The size of the data portion of a given entry by the time it is deleted.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.DeleteFailed" units="files" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Number of external files that we were unable to delete. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.DeleteHeader" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The size of the HTML headers of a given entry by the time it is deleted.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.Entries" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries currently stored on the cache. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.EntriesFull" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries currently stored on the cache, after it is full.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.EntryAccessRate" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries accessed by the cache in a 30 seconds interval.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.EntrySize" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average size of an entry. It is only measured after the cache is full,
    so evictions are taking place. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.Error" enum="DiskCacheError" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>Critical error ids. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.2.FillupAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The age of the cache (in hours) by the time we reach the size limit.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FillupTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of hours required to fill up the cache, as measured by the cache
    being running. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FirstByteIORate" units="KB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of KB accessed from the cache in a 30 seconds interval,
    by the time we reach the cache size limit. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FirstEntryAccessRate" units="entries"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average number of entries accessed by the cache in a 30 seconds
    interval, by the time we reach the cache size limit. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FirstEntrySize" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The average size of an entry by the time we reach the cache size limit.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FirstHitRatio" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio by the time we fill up the cache. Of course, we started with
    an empty cache. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.FirstLargeEntriesRatio" units="%"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the cache used by entries of more than 512 KB, by the time
    we reach the cache size limit. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.GetRankings" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent reading the LRU-related portion of an entry. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.HitRatio" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The current hit ratio. It is only measured after the cache is full, so
    evictions are taking place, and data from the fill-up period is not
    considered. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.HitRatioBySize2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each size. To calculate the hit ratio of caches of a
    certain size, take the ratio of a bin in this histogram to the same bin in
    DiskCache.2.Size2. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.HitRatioByTotalTime" units="hours"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each total time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.2.TotalTime. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.HitRatioByUseTime" units="hours"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The hit ratio for each use time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.2.UseTime. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.IndexLoad" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Percentage of the index table that is currently used (the cache is full).
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.KeySize" units="bytes" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The size of each key. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.2.LargeEntriesRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Percentage of the cache used by entries of more than 512 KB. It is only
    measured after the cache is full, so evictions are taking place.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.MaxOpenEntries2" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The maximum number of simultaneously open disk cache entries. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.MaxSize2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The maximum size of the cache. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.2.NumberOfReferences" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of open entry references at any given moment. Closely related to
    AverageOpenEntries, but this one is not the average per client but instead a
    direct histogram updated every 30 secs. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.OpenTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent opening an entry already on the cache (cache hit).
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.PendingIO" units="operations" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of pending IO operations (Async IO). Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.ReadTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent reading from an entry. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.2.ResurrectRatio" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of re-created deleted entries versus entries that we really
    don't know about. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.ShortReport" enum="ShortReportReason"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The reason for not sending a full report. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.Size2" units="MB" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The current size of the cache. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.2.TotalClearTimeV1" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent deleting the cache. (Clear browsing data). Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalClearTimeV2" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent deleting the cache. (Clear browsing data). Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalIOTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The total time it takes to perform a payload IO operation (AKA, directed to
    an entry). This is measured from the IO thread. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Number of hours that the cache has been used. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalTrimDeletedTime" units="ms"
    expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent removing deleted entries from the cache. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalTrimTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent removing old entries from the cache. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalTrimTimeV1" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent removing old entries from the cache. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TotalTrimTimeV2" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent evicting entries from the cache (moving them to the deleted
    list). Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TrimAge" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time that an entry lives in the cache without being accessed until it is
    finally purged. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TrimDeletedItems" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are deleted on a single iteration. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TrimItemsV1" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are evicted on a single iteration. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TrimItemsV2" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are evicted (moved to the deleted list) on a
    single iteration. Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.TrimRate" units="?" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The number of entries that are evicted per hour of use. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.UpdateRank" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The time spent moving an entry to the front of the LRU list. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.UsedSpace" units="%" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    The percentage of the allowed disk space that we are currently using.
    Media-specific cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.UseTime" units="hours" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>
    Number of hours that the cache has been used since last week. Media-specific
    cache.
  </summary>
</histogram>

<histogram name="DiskCache.2.WriteTime" units="ms" expires_after="M85">
  <owner>rvargas@chromium.org</owner>
  <summary>The time spent writing to an entry. Media-specific cache.</summary>
</histogram>

<histogram name="DiskCache.3.AsyncIOTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time for an async IO operation to complete. This covers content Writes
    and Reads, measured from the cache thread. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.AsyncReadDispatchTime" units="ms"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The synchronous portion of an async read. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.AsyncWriteDispatchTime" units="ms"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The synchronous portion of an async write. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.AverageOpenEntries2" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of open disk cache entries at any given time. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.BufferBytes" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The total size of all the internal buffers. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.ByteIORate" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of KB accessed from the cache in a 30 seconds interval. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.CreateTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The time spent creating a new entry on the cache. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.DeleteData" units="bytes" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The size of the data portion of a given entry by the time it is deleted.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.DeleteFailed" units="files" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Number of external files that we were unable to delete. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.Entries" units="entries" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries currently stored on the cache. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.EntriesFull" units="entries" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries currently stored on the cache, after it is full.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.EntryAccessRate" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries accessed by the cache in a 30 seconds interval.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.EntrySize" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average size of an entry. It is only measured after the cache is full,
    so evictions are taking place. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.Error" enum="DiskCacheError" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>Critical error ids. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.FillupAge" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The age of the cache (in hours) by the time we reach the size limit.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FillupTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of hours required to fill up the cache, as measured by the cache
    being running. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FirstByteIORate" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of KB accessed from the cache in a 30 seconds interval,
    by the time we reach the cache size limit. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FirstEntryAccessRate" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of entries accessed by the cache in a 30 seconds
    interval, by the time we reach the cache size limit. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FirstEntrySize" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average size of an entry by the time we reach the cache size limit.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FirstHitRatio" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio by the time we fill up the cache. Of course, we started with
    an empty cache. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.FirstLargeEntriesRatio" units="%"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The percentage of the cache used by entries of more than 512 KB, by the time
    we reach the cache size limit. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.GetRankings" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent reading the LRU-related portion of an entry. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.HitRatio" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The current hit ratio. It is only measured after the cache is full, so
    evictions are taking place, and data from the fill-up period is not
    considered. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.HitRatioBySize2" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each size. To calculate the hit ratio of caches of a
    certain size, take the ratio of a bin in this histogram to the same bin in
    DiskCache.3.Size2. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.HitRatioByTotalTime" units="hours"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each total time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.3.TotalTime. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.HitRatioByUseTime" units="hours"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each use time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.3.UseTime. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.IndexLoad" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Percentage of the index table that is currently used (the cache is full).
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.KeySize" units="bytes" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The size of each key. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.LargeEntriesRatio" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Percentage of the cache used by entries of more than 512 KB. It is only
    measured after the cache is full, so evictions are taking place. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.MaxOpenEntries2" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The maximum number of simultaneously open disk cache entries. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.MaxSize2" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The maximum size of the cache. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.OpenTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent opening an entry already on the cache (cache hit). AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.PendingIO" units="operations" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The number of pending IO operations (Async IO). AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.ReadTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The time spent reading from an entry. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.ResurrectRatio" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The percentage of re-created deleted entries versus entries that we really
    don't know about. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.ShortReport" enum="ShortReportReason"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The reason for not sending a full report. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.Size" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The current size of the cache. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.TotalIOTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The total time it takes to perform a payload IO operation (AKA, directed to
    an entry). This is measured from the IO thread. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TotalTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>Number of hours that the cache has been used. AppCache.</summary>
</histogram>

<histogram name="DiskCache.3.TotalTrimDeletedTime" units="ms"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent removing deleted entries from the cache. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TotalTrimTimeV1" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent removing old entries from the cache. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TotalTrimTimeV2" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent evicting entries from the cache (moving them to the deleted
    list). AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TrimAge" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time that an entry lives in the cache without being accessed until it is
    finally purged. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TrimDeletedItems" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are deleted on a single iteration. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TrimItemsV1" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are evicted on a single iteration. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TrimItemsV2" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are evicted (moved to the deleted list) on a
    single iteration. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.TrimRate" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are evicted per hour of use. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.UpdateRank" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent moving an entry to the front of the LRU list. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.UsedSpace" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The percentage of the allowed disk space that we are currently using.
    AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.UseTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Number of hours that the cache has been used since last week. AppCache.
  </summary>
</histogram>

<histogram name="DiskCache.3.WriteTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The time spent writing to an entry. AppCache.</summary>
</histogram>

<histogram name="DiskCache.4.AsyncIOTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time for an async IO operation to complete. This covers content Writes
    and Reads, measured from the cache thread. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.AsyncReadDispatchTime" units="ms"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The synchronous portion of an async read. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.AsyncWriteDispatchTime" units="ms"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The synchronous portion of an async write. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.AverageOpenEntries2" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of open disk cache entries at any given time.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.BufferBytes" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The total size of all the internal buffers. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.ByteIORate" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of KB accessed from the cache in a 30 seconds interval.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.CreateTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent creating a new entry on the cache. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.DeleteData" units="bytes" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The size of the data portion of a given entry by the time it is deleted.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.DeleteFailed" units="files" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Number of external files that we were unable to delete. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.DeleteHeader" units="bytes" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The size of the HTML headers of a given entry by the time it is deleted.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.Entries" units="entries" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries currently stored on the cache. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.EntriesFull" units="entries" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries currently stored on the cache, after it is full.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.EntryAccessRate" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries accessed by the cache in a 30 seconds interval.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.EntrySize" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average size of an entry. It is only measured after the cache is full,
    so evictions are taking place. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.Error" enum="DiskCacheError" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>Critical error ids. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.FillupAge" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The age of the cache (in hours) by the time we reach the size limit.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FillupTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of hours required to fill up the cache, as measured by the cache
    being running. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FirstByteIORate" units="KB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of KB accessed from the cache in a 30 seconds interval,
    by the time we reach the cache size limit. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FirstEntryAccessRate" units="entries"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average number of entries accessed by the cache in a 30 seconds
    interval, by the time we reach the cache size limit. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FirstEntrySize" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The average size of an entry by the time we reach the cache size limit.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FirstHitRatio" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio by the time we fill up the cache. Of course, we started with
    an empty cache. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.FirstLargeEntriesRatio" units="%"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The percentage of the cache used by entries of more than 512 KB, by the time
    we reach the cache size limit. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.GetRankings" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent reading the LRU-related portion of an entry. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.HitRatio" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The current hit ratio. It is only measured after the cache is full, so
    evictions are taking place, and data from the fill-up period is not
    considered. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.HitRatioBySize2" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each size. To calculate the hit ratio of caches of a
    certain size, take the ratio of a bin in this histogram to the same bin in
    DiskCache.4.Size2. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.HitRatioByTotalTime" units="hours"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each total time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.4.TotalTime. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.HitRatioByUseTime" units="hours"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The hit ratio for each use time. To calculate the hit ratio of caches of a
    certain age, take the ratio of a bin in this histogram to the same bin in
    DiskCache.4.UseTime. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.IndexLoad" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Percentage of the index table that is currently used (the cache is full).
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.KeySize" units="bytes" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The size of each key. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.LargeEntriesRatio" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Percentage of the cache used by entries of more than 512 KB. It is only
    measured after the cache is full, so evictions are taking place.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.MaxOpenEntries2" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The maximum number of simultaneously open disk cache entries. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.MaxSize2" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The maximum size of the cache. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.OpenTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent opening an entry already on the cache (cache hit).
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.PendingIO" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of pending IO operations (Async IO). ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.ReadTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The time spent reading from an entry. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.ShortReport" enum="ShortReportReason"
    expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The reason for not sending a full report. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.Size" units="MB" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The current size of the cache. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.TotalIOTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The total time it takes to perform a payload IO operation (AKA, directed to
    an entry). This is measured from the IO thread. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.TotalTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>Number of hours that the cache has been used. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.4.TotalTrimTimeV1" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent removing old entries from the cache. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.TrimAge" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time that an entry lives in the cache without being accessed until it is
    finally purged. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.TrimItemsV1" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are evicted on a single iteration. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.TrimRate" units="?" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The number of entries that are evicted per hour of use. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.UpdateRank" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The time spent moving an entry to the front of the LRU list. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.UsedSpace" units="%" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    The percentage of the allowed disk space that we are currently using.
    ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.UseTime" units="hours" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>
    Number of hours that the cache has been used since last week. ShaderCache.
  </summary>
</histogram>

<histogram name="DiskCache.4.WriteTime" units="ms" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The time spent writing to an entry. ShaderCache.</summary>
</histogram>

<histogram name="DiskCache.DeleteFailed2" units="files" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>Number of block-files that we were unable to delete.</summary>
</histogram>

<histogram name="DiskCache.Experiment" units="group" expires_after="M79">
  <owner>Please list the metric's owners. Add more owner tags as needed.</owner>
  <summary>The experiment group for this user.</summary>
</histogram>

<histogram name="DiskCache.SizeStats" units="?" expires_after="M85">
  <owner>dmikurube@chromium.org</owner>
  <summary>The size distribution of data stored on the cache.</summary>
</histogram>

</histograms>

</histogram-configuration>