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Message-ID: <20060111192056.67364.qmail@web34113.mail.mud.yahoo.com>
Date: Wed, 11 Jan 2006 11:20:56 -0800 (PST)
From: Kenny Simpson <theonetruekenny@yahoo.com>
Subject: Re: Is user-space AIO dead?
To: David Lloyd <dmlloyd@tds.net>
Cc: linux kernel <linux-kernel@vger.kernel.org>
In-Reply-To: <Pine.LNX.4.64.0601111304390.14191@tomservo.workpc.tds.net>
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--- David Lloyd <dmlloyd@tds.net> wrote:

> On Wed, 11 Jan 2006, Kenny Simpson wrote:
> 
> > --- David Lloyd <dmlloyd@tds.net> wrote:
> >> Wouldn't nonblocking I/O on regular files be nice?
> >
> > Yes it could be.  As I understand it, regular file writes (not O_DIRECT) 
> > are only to the page cache and only block when there is memory pressure 
> > (so it is more of a throttle).
> 
> If you were however using O_DIRECT or O_SYNC, you would then have a 
> mechanism to know when your writes have made it to disk, which might be 
> useful for transactional systems.

Right, but I'm not sure O_DIRECT implies stable storage, only data sent out to the device, not
held up in the page cache (I could be wrong).

AIO is implemented for O_DIRECT according to the paper, but they observed it not having benefit.

AIO being implemented to O_SYNC would be nice for my use, as it would also eliminate the extra
alignment restrictions brought on by O_DIRECT.

-Kenny


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