block: add support for IO CPU affinity

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This patch adds support for controlling the IO completion CPU of
either all requests on a queue, or on a per-request basis. We export
a sysfs variable (rq_affinity) which, if set, migrates completions
of requests to the CPU that originally submitted it. A 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.

This requires a little help from the architecture, so it'll only
work as designed for archs that are using the new generic smp
helper infrastructure.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

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This commit is contained in:

Jens Axboe 2008-09-13 20:26:01 +02:00

parent 18887ad910

commit c7c22e4d5c

9 changed files with 182 additions and 60 deletions

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include/linux/blkdev.h

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