Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Ronen Hod
On 07/17/2012 12:21 PM, Asias He wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Asias He
On 07/17/2012 09:02 PM, Paolo Bonzini wrote: Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: Knowing the answer to that is important before anyone can say whether

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Stefan Hajnoczi
On Wed, Jul 18, 2012 at 9:12 AM, Asias He wrote: > On 07/17/2012 07:11 PM, Stefan Hajnoczi wrote: >> >> On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: >>> >>> On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: > > > So, vhost-blk

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Asias He
On 07/17/2012 07:11 PM, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Asias He
On 07/17/2012 07:11 PM, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Stefan Hajnoczi
On Wed, Jul 18, 2012 at 9:12 AM, Asias He as...@redhat.com wrote: On 07/17/2012 07:11 PM, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Asias He
On 07/17/2012 09:02 PM, Paolo Bonzini wrote: Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin m...@redhat.com wrote: Knowing the answer to that is important before anyone

Re: [PATCH 0/5] Add vhost-blk support

2012-07-18 Thread Ronen Hod
On 07/17/2012 12:21 PM, Asias He wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 03:02:45PM +0200, Paolo Bonzini wrote: > Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: > > On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: > >> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin > >> wrote: > Knowing the answer to that is

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: > On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: >> On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: Knowing the answer to that is important before anyone can say whether this approach is good or not.

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: > On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: > >> Knowing the answer to that is important before anyone can say whether > >> this approach is good or not. > >> > >> Stefan > > > > Why is it? > > Because there might

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin wrote: >> Knowing the answer to that is important before anyone can say whether >> this approach is good or not. >> >> Stefan > > Why is it? Because there might be a fix to kvmtool which closes the gap. It would be embarassing if vhost-blk

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:42:13PM +0100, Stefan Hajnoczi wrote: > On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin wrote: > > On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: > >> On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: > >> > On 07/17/2012 04:52 PM, Paolo Bonzini

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:42 PM, Stefan Hajnoczi wrote: > On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin wrote: >> On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: >>> On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: >>> > On 07/17/2012 04:52 PM, Paolo Bonzini wrote: >>>

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin wrote: > On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: >> On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: >> > On 07/17/2012 04:52 PM, Paolo Bonzini wrote: >> >> >> >> Il 17/07/2012 10:29, Asias He ha scritto: >> >>> >>

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 9:29 AM, Asias He wrote: > On 07/16/2012 07:58 PM, Stefan Hajnoczi wrote: >> Does the vhost-blk implementation do anything fundamentally different >> from userspace? Where is the overhead that userspace virtio-blk has? > > > > Currently, no. But we could play with bio

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: > On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: > > On 07/17/2012 04:52 PM, Paolo Bonzini wrote: > >> > >> Il 17/07/2012 10:29, Asias He ha scritto: > >>> > >>> So, vhost-blk at least saves ~6 syscalls for us in each request. >

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 10:21 AM, Asias He wrote: > On 07/17/2012 04:52 PM, Paolo Bonzini wrote: >> >> Il 17/07/2012 10:29, Asias He ha scritto: >>> >>> So, vhost-blk at least saves ~6 syscalls for us in each request. >> >> >> Are they really 6? If I/O is coalesced by a factor of 3, for example

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:56:31PM +0200, Paolo Bonzini wrote: > Il 17/07/2012 12:49, Michael S. Tsirkin ha scritto: > >> Ok, that would make more sense. One difference between vhost-blk and > >> vhost-net is that for vhost-blk there are also management actions that > >> would trigger the switch,

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 12:49, Michael S. Tsirkin ha scritto: >> Ok, that would make more sense. One difference between vhost-blk and >> vhost-net is that for vhost-blk there are also management actions that >> would trigger the switch, for example a live snapshot. >> So a prerequisite for vhost-blk would

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:14:33PM +0200, Paolo Bonzini wrote: > Il 17/07/2012 11:45, Michael S. Tsirkin ha scritto: > >> So it begs the question, is it going to be used in production, or just a > >> useful reference tool? > > > > Sticking to raw already makes virtio-blk faster, doesn't it? > >

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 11:45, Michael S. Tsirkin ha scritto: >> So it begs the question, is it going to be used in production, or just a >> useful reference tool? > > Sticking to raw already makes virtio-blk faster, doesn't it? > In that vhost-blk looks to me like just another optimization option. >

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 11:32:45AM +0200, Paolo Bonzini wrote: > Il 17/07/2012 11:21, Asias He ha scritto: > >> It depends. Like vhost-scsi, vhost-blk has the problem of a crippled > >> feature set: no support for block device formats, non-raw protocols, > >> etc. This makes it different from

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 10:52:10AM +0200, Paolo Bonzini wrote: > Il 17/07/2012 10:29, Asias He ha scritto: > > So, vhost-blk at least saves ~6 syscalls for us in each request. > > Are they really 6? If I/O is coalesced by a factor of 3, for example > (i.e. each exit processes 3 requests), it's

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 11:21, Asias He ha scritto: >> It depends. Like vhost-scsi, vhost-blk has the problem of a crippled >> feature set: no support for block device formats, non-raw protocols, >> etc. This makes it different from vhost-net. > > Data-plane qemu also has this cripppled feature set

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Asias He
On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3 requests), it's really 2 syscalls per

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 10:29, Asias He ha scritto: > So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3 requests), it's really 2 syscalls per request. Also, is there anything we can improve?

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Asias He
On 07/16/2012 07:58 PM, Stefan Hajnoczi wrote: On Thu, Jul 12, 2012 at 4:35 PM, Asias He wrote: This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Asias He
On 07/16/2012 07:58 PM, Stefan Hajnoczi wrote: On Thu, Jul 12, 2012 at 4:35 PM, Asias He as...@redhat.com wrote: This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15%

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3 requests), it's really 2 syscalls per request. Also, is there anything we can improve?

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Asias He
On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3 requests), it's really 2 syscalls per

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 11:21, Asias He ha scritto: It depends. Like vhost-scsi, vhost-blk has the problem of a crippled feature set: no support for block device formats, non-raw protocols, etc. This makes it different from vhost-net. Data-plane qemu also has this cripppled feature set problem, no?

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 10:52:10AM +0200, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example (i.e. each exit processes 3 requests), it's really

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 11:32:45AM +0200, Paolo Bonzini wrote: Il 17/07/2012 11:21, Asias He ha scritto: It depends. Like vhost-scsi, vhost-blk has the problem of a crippled feature set: no support for block device formats, non-raw protocols, etc. This makes it different from vhost-net.

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 11:45, Michael S. Tsirkin ha scritto: So it begs the question, is it going to be used in production, or just a useful reference tool? Sticking to raw already makes virtio-blk faster, doesn't it? In that vhost-blk looks to me like just another optimization option. Ideally I

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:14:33PM +0200, Paolo Bonzini wrote: Il 17/07/2012 11:45, Michael S. Tsirkin ha scritto: So it begs the question, is it going to be used in production, or just a useful reference tool? Sticking to raw already makes virtio-blk faster, doesn't it? In that

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 12:49, Michael S. Tsirkin ha scritto: Ok, that would make more sense. One difference between vhost-blk and vhost-net is that for vhost-blk there are also management actions that would trigger the switch, for example a live snapshot. So a prerequisite for vhost-blk would be that

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:56:31PM +0200, Paolo Bonzini wrote: Il 17/07/2012 12:49, Michael S. Tsirkin ha scritto: Ok, that would make more sense. One difference between vhost-blk and vhost-net is that for vhost-blk there are also management actions that would trigger the switch, for

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request. Are they really 6? If I/O is coalesced by a factor of 3, for example

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha scritto: So, vhost-blk at least saves ~6 syscalls for us in each request.

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 9:29 AM, Asias He as...@redhat.com wrote: On 07/16/2012 07:58 PM, Stefan Hajnoczi wrote: Does the vhost-blk implementation do anything fundamentally different from userspace? Where is the overhead that userspace virtio-blk has? Currently, no. But we could play with

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin m...@redhat.com wrote: On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012 04:52 PM, Paolo Bonzini wrote: Il 17/07/2012 10:29, Asias He ha

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:42 PM, Stefan Hajnoczi stefa...@gmail.com wrote: On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin m...@redhat.com wrote: On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 12:42:13PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:26 PM, Michael S. Tsirkin m...@redhat.com wrote: On Tue, Jul 17, 2012 at 12:11:15PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 10:21 AM, Asias He as...@redhat.com wrote: On 07/17/2012

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Stefan Hajnoczi
On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin m...@redhat.com wrote: Knowing the answer to that is important before anyone can say whether this approach is good or not. Stefan Why is it? Because there might be a fix to kvmtool which closes the gap. It would be embarassing if

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin m...@redhat.com wrote: Knowing the answer to that is important before anyone can say whether this approach is good or not. Stefan Why is it? Because there might be

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Paolo Bonzini
Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin m...@redhat.com wrote: Knowing the answer to that is important before anyone can say whether this approach is good or not.

Re: [PATCH 0/5] Add vhost-blk support

2012-07-17 Thread Michael S. Tsirkin
On Tue, Jul 17, 2012 at 03:02:45PM +0200, Paolo Bonzini wrote: Il 17/07/2012 14:48, Michael S. Tsirkin ha scritto: On Tue, Jul 17, 2012 at 01:03:39PM +0100, Stefan Hajnoczi wrote: On Tue, Jul 17, 2012 at 12:54 PM, Michael S. Tsirkin m...@redhat.com wrote: Knowing the answer to that is

Re: [PATCH 0/5] Add vhost-blk support

2012-07-16 Thread Stefan Hajnoczi
On Thu, Jul 12, 2012 at 4:35 PM, Asias He wrote: > This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk > device accelerator. Compared to userspace virtio-blk implementation, vhost-blk > gives about 5% to 15% performance improvement. Why is it 5-15% faster? vhost-blk and

Re: [PATCH 0/5] Add vhost-blk support

2012-07-16 Thread Stefan Hajnoczi
On Thu, Jul 12, 2012 at 4:35 PM, Asias He as...@redhat.com wrote: This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance improvement. Why is it 5-15% faster?

Re: [PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Asias He
Hello Jeff, On 07/13/2012 12:06 AM, Jeff Moyer wrote: Asias He writes: Hi folks, This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance improvement. Asias He

Re: [PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Jeff Moyer
Asias He writes: > Hi folks, > > This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk > device accelerator. Compared to userspace virtio-blk implementation, vhost-blk > gives about 5% to 15% performance improvement. > > Asias He (5): > aio: Export symbols and struct

[PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Asias He
Hi folks, This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance improvement. Asias He (5): aio: Export symbols and struct kiocb_batch for in kernel aio usage

Re: [PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Asias He
Hello Jeff, On 07/13/2012 12:06 AM, Jeff Moyer wrote: Asias He as...@redhat.com writes: Hi folks, This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance

[PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Asias He
Hi folks, This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance improvement. Asias He (5): aio: Export symbols and struct kiocb_batch for in kernel aio usage

Re: [PATCH 0/5] Add vhost-blk support

2012-07-12 Thread Jeff Moyer
Asias He as...@redhat.com writes: Hi folks, This patchset adds vhost-blk support. vhost-blk is a in kernel virito-blk device accelerator. Compared to userspace virtio-blk implementation, vhost-blk gives about 5% to 15% performance improvement. Asias He (5): aio: Export symbols and