IO CPU Affinity

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2.6.28 add support for controlling the IO completion CPU of either all requests on a queue, or on a per-request basis. A sysfs variable (rq_affinity) is exported which, if set, migrates completions of requests to the CPU that originally submitted it. A internal bio helper (bio_set_completion_cpu()) is also added, so that queuers can ask for completion on that specific CPU. In testing, this has been show to cut the system time by as much as 20-40% on synthetic workloads where CPU affinity is desired.


  • IO queuing and complete affinity
* http://lwn.net/Articles/268713/
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