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From Michael Dürig (JIRA) <j...@apache.org>
Subject [jira] [Commented] (OAK-5859) Analyse and reduce IO amplification by OS
Date Tue, 14 Mar 2017 12:58:41 GMT

    [ https://issues.apache.org/jira/browse/OAK-5859?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15924126#comment-15924126
] 

Michael Dürig commented on OAK-5859:
------------------------------------

OAK-5634 is a prerequisite for this issue to be able to easily monitor IO within the JVM.

> Analyse and reduce IO amplification by OS
> -----------------------------------------
>
>                 Key: OAK-5859
>                 URL: https://issues.apache.org/jira/browse/OAK-5859
>             Project: Jackrabbit Oak
>          Issue Type: Task
>          Components: segment-tar
>            Reporter: Michael Dürig
>             Fix For: 1.7.2
>
>
> Certain operation system settings might result in too much data actually being read from
disk causing early setting on of thrashing. E.g. transparent huge pages or too big read aheads
might be contra productive in combination with the TarMKs memory mapping model. 
> * Determine the ratio of data being read by the TarMK and actual data being read from
disk. Determine the impact of relevant OS parameters (e.g. transparent huge pages) on this
ratio.
> * Compare memory mapped mode with file IO mode with an accordingly increased segment
cache. This would move prediction of what is likely to be read next from the OS layer into
our segment cache eviction strategy. 



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