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https://issues.apache.org/jira/browse/CASSANDRA-19477?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Stefan Miklosovic reassigned CASSANDRA-19477:
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Assignee: Stefan Miklosovic
> Significant CPU overhead in HintsStore.getTotalFileSize
> -------------------------------------------------------
>
> Key: CASSANDRA-19477
> URL: https://issues.apache.org/jira/browse/CASSANDRA-19477
> Project: Cassandra
> Issue Type: Bug
> Components: Consistency/Hints
> Reporter: Jon Haddad
> Assignee: Stefan Miklosovic
> Priority: Normal
> Attachments: flamegraph.cpu.html
>
>
> When testing a cluster with more requests than it could handle, I noticed
> significant CPU time (25%) spent in HintsStore.getTotalFileSize. Here's what
> I'm seeing from profiling:
> 10% of CPU time spent in HintsDescriptor.fileName which only does this:
>
> {noformat}
> return String.format("%s-%s-%s.hints", hostId, timestamp, version);{noformat}
> At a bare minimum here we should create this string up front with the host
> and version and eliminate 2 of the 3 substitutions, but I think it's probably
> faster to use a StringBuilder and avoid the underlying regular expression
> altogether.
> 12% of the time is spent in org.apache.cassandra.io.util.File.length. It
> looks like this is called once for each hint file on disk for each host we're
> hinting to. In the case of an overloaded cluster, this is significant. It
> would be better if we were to track the file size in memory for each hint
> file and reference that rather than go to the filesystem.
> These fairly small changes should make Cassandra more reliable when under
> load spikes.
> CPU Flame graph attached.
> I only tested this in 4.1 but it looks like this is present up to trunk.
>
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