From: Jens Axboe <axboe@suse.de>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Arjan van de Ven <arjanv@redhat.com>,
Neil Brown <neilb@cse.unsw.edu.au>,
Christoph Hellwig <hch@lst.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: bug in md write barrier support?
Date: Thu, 9 Sep 2004 16:34:34 +0200 [thread overview]
Message-ID: <20040909143434.GA1737@suse.de> (raw)
In-Reply-To: <1094734272.14623.2.camel@localhost.localdomain>
On Thu, Sep 09 2004, Alan Cox wrote:
> On Iau, 2004-09-09 at 09:29, Jens Axboe wrote:
> > > why does this seem broken? semantics of "cache flush guarantees that all
> > > io submitted prior to it hits the spindle" are quite sane imo; no
> > > guarantee of later submitted IO.. compare the unix "sync" command; same
> > > level of semantics.
> >
> > Depends on your angle, I think it breaks the principle of least
> > surprise.
>
> As far as I can ascertain raid controllers in general follow this set of
> semantics. Its less of an issue for many of them with battery backup
> obviously.
>
> It also makes a lot of sense at the hardware level for performance
> especially when dealing with raid.
Yes. As long as the required semantics aren't explicitly guaranteed in
the specification, we should not rely on it.
--
Jens Axboe
next prev parent reply other threads:[~2004-09-09 14:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-03 17:24 bug in md write barrier support? Christoph Hellwig
2004-09-04 0:56 ` Neil Brown
2004-09-04 8:21 ` Jens Axboe
2004-09-06 1:36 ` Neil Brown
2004-09-08 9:23 ` Jens Axboe
2004-09-08 13:35 ` Alan Cox
2004-09-08 15:46 ` Jens Axboe
2004-09-08 22:21 ` Alan Cox
2004-09-09 8:06 ` Jens Axboe
2004-09-09 8:22 ` Arjan van de Ven
2004-09-09 8:29 ` Jens Axboe
2004-09-09 12:51 ` Alan Cox
2004-09-09 14:34 ` Jens Axboe [this message]
2004-09-12 17:13 ` Rogier Wolff
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