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Posted to dev@qpid.apache.org by "ASF subversion and git services (JIRA)" <ji...@apache.org> on 2017/08/22 15:07:00 UTC
[jira] [Commented] (QPID-7895) [linearstore] Excessive CPU
utilization for some kernel clocksources
[ https://issues.apache.org/jira/browse/QPID-7895?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16136911#comment-16136911 ]
ASF subversion and git services commented on QPID-7895:
-------------------------------------------------------
Commit 4e98f6c08ef531e15217f812f6624f18cf2d50fb in qpid-cpp's branch refs/heads/master from [~kpvdr]
[ https://git-wip-us.apache.org/repos/asf?p=qpid-cpp.git;h=4e98f6c ]
QPID-7895: Update to linearstore to make the flush timer more intelligent and only run when there is flushable content in the write buffers
> [linearstore] Excessive CPU utilization for some kernel clocksources
> --------------------------------------------------------------------
>
> Key: QPID-7895
> URL: https://issues.apache.org/jira/browse/QPID-7895
> Project: Qpid
> Issue Type: Bug
> Components: C++ Broker
> Reporter: Kim van der Riet
> Assignee: Kim van der Riet
>
> For some kernel clocksources (eg acpi_pm), it has been observed that there is an excessively high CPU utilization which correlates with the linearstore's flush timeout being set to a very low value (100us). This is a problem for some customers which require almost instant flush to obtain pseudo-synchronous store behavior (hence the 100us flush timer) and run many brokers (up to hundreds) on a single machine. In these cases, the CPU is 100% utilized.
> A check of the source shows that the flush timer is firing continuously, irrespective of whether any disk I/O has taken place.
> It is proposed that a change to linearstore be made which will only run the timer when needed (ie while there is content in the write buffers that needs flushing).
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