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Date:	Wed, 10 Mar 2010 08:21:51 -0500
From:	Jeff Moyer <jmoyer@...hat.com>
To:	M vd S <mvds.00@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: O_NONBLOCK is NOOP on block devices

M vd S <mvds.00@...il.com> writes:
> I also briefly tried aio_* and the libaio interface. The former is not
> really asynchronous - all requests are put in one separate thread
> where they will be executed in order, i.e. blocking, so you don't get
> any advantage from NCQ or data that was cached by the disk or the
> kernel. The latter apparently ends in an io_submit() which will block
> until all queued reads are finished, but I might have missed something
> there.

What you missed is that the native aio system calls require O_DIRECT.

Cheers,
Jeff
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