On Mon, 2012-06-18 at 14:14 +0300, Dor Laor wrote: > On 06/18/2012 01:05 PM, Rusty Russell wrote: > > On Mon, 18 Jun 2012 16:03:23 +0800, Asias He<asias@xxxxxxxxxx> wrote: > >> On 06/18/2012 03:46 PM, Rusty Russell wrote: > >>> On Mon, 18 Jun 2012 14:53:10 +0800, Asias He<asias@xxxxxxxxxx> 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. > > > > Users using a spinning disk still get IO scheduling in the host though. > > What benefit is there in doing it in the guest as well? > > The io scheduler waits for requests to merge and thus batch IOs > together. It's not important w.r.t spinning disks since the host can do > it but it causes much less vmexits which is the key issue for VMs. Is the amount of exits caused by virtio-blk significant at all with EVENT_IDX? -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
