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Add CAM I/O Scheduler report from Warner Losh <imp@bsdimp.com>.

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Warren Block 2016-04-20 01:10:07 +00:00
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Notes: svn2git 2020-12-08 03:00:23 +00:00 
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en_US.ISO8859-1/htdocs/news/status/report-2016-01-2016-03.xml
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@ -2523,4 +2523,47 @@
<a href="https://www.freebsdfoundation.org/blog/introducing-a-new-look-for-the-foundation/">new look</a>.</p>
</body>
</project>
<project cat='kern'>
<title>CAM I/O Scheduler</title>
<contact>
<person>
<name>
<given>Warner</given>
<common>Losh</common>
</name>
<email>wlosh@netflix.com</email>
</person>
</contact>
<links>
<url href="https://people.freebsd.org/~imp/bsdcan2015/iosched-v3.pdf">I/O Scheduling in FreeBSD's CAM Subsystem (PDF)</url>
<url href="https://www.youtube.com/watch?v=3WqOLolj5EU">The BSDCan 2015 Talk</url>
</links>
<body>
<p>An enhanced CAM I/O scheduler has been committed to the tree.
By default, this scheduler implements the old behavior.
However, a more adaptive scheduler can be enabled. The more
adaptive scheduler allows pacing of different types of I/O to
allow the workload-preferred I/O to experience maximum
performance. By measuring device response time at the lowest
levels, many artifacts of software queueing can be eliminated
and better performance can be achieved. In addition, Queued
Trims are now supported for SATA devices that support them.
Details about the new scheduler are available in the
<a href="https://people.freebsd.org/~imp/bsdcan2015/iosched-v3.pdf">I/O Scheduling in FreeBSD's CAM Subsystem article (PDF)</a>
or from
<a href="https://www.youtube.com/watch?v=3WqOLolj5EU">the BSDCan 2015 talk</a>.</p>
<p>In essence, this I/O scheduler allows the user to choose
improved read performance by trading off some write
performance. Or, if SSDs cannot garbage collect fast enough
to keep up with writes, to improve write performance at the
cost of some read performance.</p>
</body>
<sponsor>Netflix</sponsor>
</project>
</report>