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From "Dag H. Wanvik (JIRA)" <j...@apache.org>
Subject [jira] Updated: (DERBY-799) Large response times during checkpointing on disk-bound systems
Date Mon, 29 Jun 2009 14:43:47 GMT

     [ https://issues.apache.org/jira/browse/DERBY-799?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel

Dag H. Wanvik updated DERBY-799:

    Derby Categories: [Performance]

> Large response times during checkpointing on disk-bound systems
> ---------------------------------------------------------------
>                 Key: DERBY-799
>                 URL: https://issues.apache.org/jira/browse/DERBY-799
>             Project: Derby
>          Issue Type: Improvement
>          Components: Store
>    Affects Versions:,,,
>         Environment: Observed on both Solaris and Linux with Sun VM.
>            Reporter: Øystein Grøvlen
> We have observed that during checkpointing, transaction response times for small transactions
may become very long.  Extra trace output in the log showed that this was due to long response
times for disk I/O.  I observed that some read and write operations took more than 20 seconds.
> The believed reason for the long response times is that the file system buffer may be
overflowed during checkpointing.  During checkpointing, Derby writes all dirty pages to the
file system buffer and then syncs at the end.  I tried syncing a file for every 100th write
and that improved the situation a bit.
> The following derby-dev threads discusses this issue:
> http://www.nabble.com/-jira-Created%3A-%28DERBY-733%29-Starvation-in-RAFContainer.readPage%28%29-t646257.html#a1975574
> http://www.nabble.com/Derby-I-O-issues-during-checkpointing-t473523.html#a1294290
> I will file another JIRA issue for the related issue of concurrent access to the same

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