From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Daniel Stodden <daniel.stodden@citrix.com>,
"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>,
"jaxboe@fusionio.com" <jaxboe@fusionio.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"konrad@kernel.org" <konrad@kernel.org>
Subject: Re: [Xen-devel] Re: [PATCH] xen block backend driver. - proper flush/barrier/fua support missing.
Date: Mon, 2 May 2011 15:08:43 -0400 [thread overview]
Message-ID: <20110502190843.GA29913@dumpdata.com> (raw)
In-Reply-To: <20110422090904.GA29246@infradead.org>
On Fri, Apr 22, 2011 at 05:09:04AM -0400, Christoph Hellwig wrote:
> On Thu, Apr 21, 2011 at 12:14:37PM -0700, Daniel Stodden wrote:
> > > There is a huge userbase of guests out there that does rely on it.
> >
> > Which ones? Old blkfront would have make a difference back then when
> > barriers used to be an option, but it never actually declared it, right?
>
> Pre-Linux 2.6.37 guests using reiserfs actually relied on the queue
> flushing. This includes a lot of SLES installation which are still
> in common use. There's only two options to make sure they work:
>
> (1) keep the original barrier semantics and flush the queue
> (2) do not advertize "barrier" support at all, and make sure to submit
> every I/O we get with the FUA bit.
>
> In practice (2) is going to be faster for most real-life workloads. So
> maybe you should just drop the old "barrier" support and just send
> requests with the FUA bit set for now, until you have proper flush
> and fua support in the protocol.
Let me play with both options and see how they pan out.
Christoph,
Is there a good tool to unmask barrier bugs? I found this one:
http://lwn.net/Articles/283169/
but not sure if that still applies to this case? Or does
running bonnie++ expose the potential issues?
next prev parent reply other threads:[~2011-05-02 19:08 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-20 21:05 [PATCH v3] xen block backend Konrad Rzeszutek Wilk
2011-04-20 21:05 ` [PATCH] xen block backend driver Konrad Rzeszutek Wilk
2011-04-21 3:40 ` Christoph Hellwig
2011-04-21 19:03 ` [Xen-devel] " Daniel Stodden
2011-04-21 19:06 ` Christoph Hellwig
2011-04-21 19:14 ` [Xen-devel] " Daniel Stodden
2011-04-22 9:09 ` Christoph Hellwig
2011-05-02 19:08 ` Konrad Rzeszutek Wilk [this message]
2011-04-21 3:37 ` [PATCH v3] xen block backend Christoph Hellwig
2011-04-21 7:28 ` [Xen-devel] " Ian Campbell
2011-04-21 8:03 ` Ian Campbell
2011-04-21 8:06 ` Christoph Hellwig
2011-04-21 8:38 ` Ian Campbell
2011-04-21 8:04 ` [Xen-devel] " Christoph Hellwig
2011-04-27 22:06 ` Konrad Rzeszutek Wilk
2011-04-28 19:29 ` Pasi Kärkkäinen
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