From: Jens Axboe <jens.axboe@oracle.com>
To: jidong xiao <jidong.xiao@gmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: What does "ordering by draining" mean?
Date: Mon, 10 Dec 2007 11:37:56 +0100 [thread overview]
Message-ID: <20071210103753.GB5008@kernel.dk> (raw)
In-Reply-To: <4104961b0712100149h69b1e1fas355b770f93affd03@mail.gmail.com>
On Mon, Dec 10 2007, jidong xiao wrote:
> Hi,
>
> I am reading the source code of block I/O layer, and now seeing there
> saying "ordering by draining" or "ordering by tag" in
> include/blkdev.h,and the comments in that file says: "Hardbarrier is
> supported with one of the following methods", but what do these two
> methods exactly mean?
ordering by draining means that you empty the pending queue of requests
and then flush the cache to prevent a later issue of a new request to
reach the platter before the older ones. order by tag means that the hw
has a way of being told not to reorder beyond the barrier, in which case
you don't have to drain the queue.
--
Jens Axboe
next prev parent reply other threads:[~2007-12-10 10:41 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-12-10 9:49 What does "ordering by draining" mean? jidong xiao
2007-12-10 10:37 ` Jens Axboe [this message]
2007-12-27 13:23 ` jidong xiao
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