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https://issues.apache.org/jira/browse/CASSANDRA-9240?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14516769#comment-14516769
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Branimir Lambov edited comment on CASSANDRA-9240 at 4/28/15 10:22 AM:
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Before 8464 reads from disk were explicit, after 8464 the data is memory-mapped
hence their time share is accounted for in whatever happens to be using the
data. In this case that's LZ4Compressor.uncompress.
More time spent in it now means data being read more slowly. Could it be that
the OS is evicting memory-mapped pages from cache when the application that
owns them closes?
was (Author: blambov):
Before 8464 reads from disk were explicit, after 8464 the data is memory-mapped
hence their time share is accounted for in whatever happens to be reading the
data. In this case that's LZ4Compressor.uncompress.
More time spent in it now means data being read more slowly. Could it be that
the OS is evicting memory-mapped pages from cache when the application that
owns them closes?
> Performance issue after a restart
> ---------------------------------
>
> Key: CASSANDRA-9240
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9240
> Project: Cassandra
> Issue Type: Bug
> Reporter: Alan Boudreault
> Assignee: Branimir Lambov
> Fix For: 3.0
>
> Attachments: Cassandra.snapshots.zip,
> cassandra_2.1.4-clientrequest-read.log, cassandra_2.1.4.log,
> cassandra_2.1.5-clientrequest-read.log, cassandra_2.1.5.log,
> cassandra_trunk-clientrequest-read.log, cassandra_trunk.log,
> cassandra_trunk_no_restart-clientrequest-read.log,
> cassandra_trunk_no_restart.log, issue.yaml, run_issue.sh, trace_query.cql
>
>
> I have noticed a performance issue while I was working on compaction perf
> tests for CASSANDRA-7409. The performance for my use case is very bad after a
> restart. It is mostly a read performance issue but not strictly. I have
> attached my use case (see run_issue.sh and issue.yaml) and all test logs for
> 2.1.4, 2.1.5 and trunk:
> * 2.1.* are OK (although 2.1.4 seems to be better than 2.1.5?): ~6-7k
> ops/second and ~2-2.5k of read latency.
> * trunk is NOT OK: ~1.5-2k ops/second and 25-30k of read latency.
> * trunk is OK without a restart: ~ same perf than 2.1.4 and 2.1.5.
> EDIT: branch cassandra-2.1 is OK.
> I can help to bisect and/or profile on Monday if needed.
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