From mboxrd@z Thu Jan 1 00:00:00 1970 From: Asias He Subject: Re: [PATCH 3/3] virtio-blk: Add bio-based IO path for virtio-blk Date: Tue, 19 Jun 2012 10:21:34 +0800 Message-ID: <4FDFE22E.3030003@redhat.com> References: <1340002390-3950-1-git-send-email-asias@redhat.com> <1340002390-3950-4-git-send-email-asias@redhat.com> <87hau9yse7.fsf@rustcorp.com.au> <4FDEE0CB.1030505@redhat.com> <20120618101349.GC23134@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; Format="flowed" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120618101349.GC23134@redhat.com> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: virtualization-bounces@lists.linux-foundation.org Errors-To: virtualization-bounces@lists.linux-foundation.org To: "Michael S. Tsirkin" Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Christoph Hellwig List-Id: virtualization@lists.linuxfoundation.org On 06/18/2012 06:13 PM, Michael S. Tsirkin wrote: > On Mon, Jun 18, 2012 at 04:03:23PM +0800, Asias He wrote: >> On 06/18/2012 03:46 PM, Rusty Russell wrote: >>> On Mon, 18 Jun 2012 14:53:10 +0800, Asias He wrote: >>>> This patch introduces bio-based IO path for virtio-blk. >>> >>> Why make it optional? >> >> request-based IO path is useful for users who do not want to bypass >> the IO scheduler in guest kernel, e.g. users using spinning disk. >> For users using fast disk device, e.g. SSD device, they can use >> bio-based IO path. > > OK I guess but then it should be per-device. There could be > a mix of slow and fast disks :) Yes, per-device might be useful. There are issues which need solving. - How do we tell the drive which IO path to use - Device add some flag - Old qemu/lkvm can not turn this feature on - Through /sys filesystem attribute - How do we handle the switch from one path to anther. So, let's add the per-device feature later. -- Asias