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authorJeff Moyer2011-11-02 13:40:10 -0700
committerLinus Torvalds2011-11-02 16:07:03 -0700
commit080d676de095a14ecba14c0b9a91acb5bbb634df (patch)
tree4a4c56bc86a8edf4a42f8ec7c65ba795997e50ab /arch/ia64
parent2ca02df6b098be2d33a99a65531dcd84a10b6e21 (diff)
aio: allocate kiocbs in batches
In testing aio on a fast storage device, I found that the context lock takes up a fair amount of cpu time in the I/O submission path. The reason is that we take it for every I/O submitted (see __aio_get_req). Since we know how many I/Os are passed to io_submit, we can preallocate the kiocbs in batches, reducing the number of times we take and release the lock. In my testing, I was able to reduce the amount of time spent in _raw_spin_lock_irq by .56% (average of 3 runs). The command I used to test this was: aio-stress -O -o 2 -o 3 -r 8 -d 128 -b 32 -i 32 -s 16384 <dev> I also tested the patch with various numbers of events passed to io_submit, and I ran the xfstests aio group of tests to ensure I didn't break anything. Signed-off-by: Jeff Moyer <jmoyer@redhat.com> Cc: Daniel Ehrenberg <dehrenberg@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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