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From "Justin Ross (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (QPID-7895) [linearstore] Excessive CPU utilization for some kernel clocksources
Date Fri, 22 Sep 2017 00:16:00 GMT

    [ https://issues.apache.org/jira/browse/QPID-7895?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16175697#comment-16175697
] 

Justin Ross commented on QPID-7895:
-----------------------------------

[~kpvdr]?

> [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
>             Fix For: qpid-cpp-1.37.0
>
>
> 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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