From: Jens Axboe <jens.axboe@oracle.com>
To: V P <upathiyayan@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: REQ_HARDBARRIER and REQ_SOFTBARRIER
Date: Sat, 24 Feb 2007 13:42:06 +0100 [thread overview]
Message-ID: <20070224124206.GG22586@kernel.dk> (raw)
In-Reply-To: <c9ad85600702240156g717d49cfm9c7ea30c00d48d28@mail.gmail.com>
On Sat, Feb 24 2007, V P wrote:
> Hi,
>
> I'm trying to modify the ordering of I/O requests in Linux kernel, and
> came across the barrier flags REQ_HARDBARRIER and REQ_SOFTBARRIER.
>
> One thing I noticed (which might be wrong) is that all the requests
> have both these flags set. What is the significance of these flags? Is
Uhm? That's definitely not true.
> it a must for a request to have this? Can I reorder two requests with
> these flags set? How is SOFTBARRIER different from HARDBARRIER?
Both imply a reordering barrier in the io scheduler, and the hard
barrier further implies a barrier at the drive/driver side. So you may
not reorder across a barrier.
--
Jens Axboe
prev parent reply other threads:[~2007-02-24 12:42 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-24 9:56 REQ_HARDBARRIER and REQ_SOFTBARRIER V P
2007-02-24 12:42 ` Jens Axboe [this message]
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