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https://issues.apache.org/jira/browse/HBASE-29218?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Nick Dimiduk updated HBASE-29218:
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Fix Version/s: 2.7.0
> Reduce calls to Configuration#get() in decompression path
> ---------------------------------------------------------
>
> Key: HBASE-29218
> URL: https://issues.apache.org/jira/browse/HBASE-29218
> Project: HBase
> Issue Type: Improvement
> Reporter: Charles Connell
> Assignee: Charles Connell
> Priority: Minor
> Labels: pull-request-available
> Fix For: 2.7.0, 3.0.0-beta-2, 2.6.3, 2.5.12
>
> Attachments: slow-decompressor-reinit.1.html,
> slow-decompressor-reinit.2.html
>
>
> Part of a series of changes from me dedicated to improving decompression
> speed (HBASE-29123, HBASE-29135, HBASE-29193). Use of the
> {{org.apache.hadoop.conf.Configuration}} class to look up values is not super
> fast. It's fine most of the time, but in a very hot code path, it takes up
> noticeable CPU time.
> {{ByteBuffDecompressor}} 's are pooled and reused to avoid garbage collection
> churn. This means that sometimes their settings are not right for the block
> they're being asked to decompress. To handle this, before every decompression
> action, we call {{ByteBuffDecompressor#reinit(Configuration)}}, so it can
> pull settings from the Configuration in preparation for the decompression
> it's about to do. The
> {{Configuration#get()}} inside {{reinit()}} happens once per block, even
> though the settings it deals with are consistent across an entire table. This
> uses a lot of CPU cycles unnecessarily. I've attached two flamegraphs from
> RegionServers at my company that do a heavy amount of decompression. One was
> taken from a period of notable slowness for that server, and one was taken
> randomly at a "normal" time. In both profiles, {{reinit()}} accounts for 2-3%
> of CPU time.
> Because the settings used by a {{ByteBuffDecompressor}} don't actually change
> within a table, we can pull the settings it needs from a {{Configuration}}
> when opening the HFile, and then not check again. Attached is a PR to do so,
> which will save us 2-3% of our CPU cycles in decompression-heavy workloads.
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