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Date: Thu, 22 Sep 2011 17:33:29 -0700 From: Daniel Ehrenberg <dehrenberg@...gle.com> To: Jeff Moyer <jmoyer@...hat.com> Cc: linux-kernel@...r.kernel.org, linux-aio@...ck.org, Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [patch, v3] aio: allocate kiocbs in batches On Thu, Sep 22, 2011 at 9:41 AM, Jeff Moyer <jmoyer@...hat.com> wrote: > Hi, > > 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. > This patch looks great! It produces a significant speedup on a benchmark I care about. I have been looking into improving the efficiency of io_submit, and I believe there is still more work that can be done. Dan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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