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https://issues.apache.org/jira/browse/SOLR-10130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15865492#comment-15865492
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Andrzej Bialecki commented on SOLR-10130:
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I would've expected a much larger difference with this patch, if this indeed
was the cause of the slowdown - the patch completely turns off metrics
collection at directory and index level.
bq. With 6.4.0, we were handling 6000 requests/minute. With 6.4.1 it is 1000 rpm
[~wunder] This is odd, too - the same metrics code is present in both 6.4.1 and
6.4.0, with the same defaults, so I would expect that both versions should show
similar performance. Could you please collect some stacktraces (or sample /
profile) to verify that you see the same hotspots as [~emaijala] ?
> Serious performance degradation in Solr 6.4.1 due to the new metrics
> collection
> -------------------------------------------------------------------------------
>
> Key: SOLR-10130
> URL: https://issues.apache.org/jira/browse/SOLR-10130
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Components: metrics
> Affects Versions: 6.4.1
> Environment: Centos 7, OpenJDK 1.8.0 update 111
> Reporter: Ere Maijala
> Assignee: Andrzej Bialecki
> Priority: Blocker
> Labels: perfomance
> Attachments: SOLR-10130.patch, solr-8983-console-f1.log
>
>
> We've stumbled on serious performance issues after upgrading to Solr 6.4.1.
> Looks like the new metrics collection system in MetricsDirectoryFactory is
> causing a major slowdown. This happens with an index configuration that, as
> far as I can see, has no metrics specific configuration and uses
> luceneMatchVersion 5.5.0. In practice a moderate load will completely bog
> down the server with Solr threads constantly using up all CPU (600% on 6 core
> machine) capacity with a load that normally where we normally see an average
> load of < 50%.
> I took stack traces (I'll attach them) and noticed that the threads are
> spending time in com.codahale.metrics.Meter.mark. I tested building Solr
> 6.4.1 with the metrics collection disabled in MetricsDirectoryFactory getByte
> and getBytes methods and was unable to reproduce the issue.
> As far as I can see there are several issues:
> 1. Collecting metrics on every single byte read is slow.
> 2. Having it enabled by default is not a good idea.
> 3. The comment "enable coarse-grained metrics by default" at
> https://github.com/apache/lucene-solr/blob/branch_6x/solr/core/src/java/org/apache/solr/update/SolrIndexConfig.java#L104
> implies that only coarse-grained metrics should be enabled by default, and
> this contradicts with collecting metrics on every single byte read.
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