From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH 0/6][RFC] virtio-blk: Change I/O path from request to BIO
Date: Mon, 2 Jan 2012 11:23:39 -0500
Message-ID: <20120102162339.GA3593@infradead.org>
References: <1324429254-28383-1-git-send-email-minchan@kernel.org>
 <CAJSP0QW5wPYcHr02oNm8Y8=hsChEb5tJuO0ntPy9MO8EPuH=Qg@mail.gmail.com>
 <20111222234135.GB7056@barrios-laptop.redhat.com>
 <CAJSP0QWpzOGtQEULu7yz1vDEExSatGpdEPSvvDx=oNYkBveyrQ@mail.gmail.com>
 <4F01D750.7040304@redhat.com>
 <20120102161518.GA28940@infradead.org>
 <4F01D8C5.1060300@redhat.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Cc: Christoph Hellwig <hch@infradead.org>,
	Stefan Hajnoczi <stefanha@gmail.com>,
	Minchan Kim <minchan@kernel.org>,
	Rusty Russell <rusty@rustcorp.com.au>,
	Chris Wright <chrisw@sous-sol.org>,
	Jens Axboe <axboe@kernel.dk>,
	Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	Vivek Goyal <vgoyal@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Return-path: <linux-kernel-owner@vger.kernel.org>
Content-Disposition: inline
In-Reply-To: <4F01D8C5.1060300@redhat.com>
Sender: linux-kernel-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On Mon, Jan 02, 2012 at 05:18:13PM +0100, Paolo Bonzini wrote:
> >I tried a few times, and the only constant measureable
> >thing was that it regressed performance when used for rotating devices
> >in a few benchmarks.
> 
> Were you trying with cache=none or writeback?  For cache=none,
> that's exactly what I'd expect.  cache=writeback could be more
> interesting...

cache=none - cache=writeback isn't something people should ever use
except for read-only or extremly read-mostly workloads.