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https://issues.apache.org/jira/browse/SOLR-10130?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15870751#comment-15870751
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Walter Underwood commented on SOLR-10130:
-----------------------------------------
This might be part of it:
[[email protected]]# ls -lh
/solr/data/questions_shard2_replica1/data/tlog/
total 4.7G
-rw-r--r-- 1 bin bin 4.7G Feb 13 11:04 tlog.0000000000000000000
[[email protected]]# du -sh /solr/data/questions_shard2_replica1/data/*
8.4G /solr/data/questions_shard2_replica1/data/index
4.0K /solr/data/questions_shard2_replica1/data/snapshot_metadata
4.7G /solr/data/questions_shard2_replica1/data/tlog
Last Modified: 3 days ago
Num Docs: 3683075
Max Doc: 3683075
Heap Memory Usage: -1
Deleted Docs: 0
Version: 2737
Segment Count: 26
Optimized: yes
Current: yes
> 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
> Fix For: master (7.0), 6.4.2
>
> Attachments: SOLR-10130.patch, 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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