Re: [Xen-devel] [PATCH 2/2] drivers: xen/block: add multi-page ring support

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Feb 06, 2015 at 06:47:17PM +0800, Bob Liu wrote:
> 
> On 02/02/2015 06:43 PM, Roger Pau Monné wrote:
> > El 23/01/15 a les 10.14, Bob Liu ha escrit:
> >> Extend xen/block to support multi-page ring.
> >>  * xen-blkback notify blkfront with feature-multi-ring-pages
> >>  * xen-blkfront write to xenstore about how many pages are used as the ring
> >>
> >> If using 4 pages as the ring, inflight requests inscreased from 32 to 128 
> >> and
> >> IOPS improved nearly 400% on our system.
> >>
> >> Signed-off-by: Bob Liu <bob.liu@xxxxxxxxxx>
> >> ---
> >>  drivers/block/xen-blkback/xenbus.c |   86 
> >> +++++++++++++++++++++++++--------
> >>  drivers/block/xen-blkfront.c       |   94 
> >> ++++++++++++++++++++++++++----------
> > 
> > This requires a patch to xen/include/public/io/blkif.h in the Xen
> > repository describing how this protocol extension is going to work
> > before reviewing the Linux implementation.
> > 
> 
> But there is no protocol change, just add an parameter "max_ring_pages"
> to control how many pages can be used as the ring. Now with one page we
> can only have 32 requests.
> 

I think Roger meant the xenbus protocol used to negotiate this feature,
not the data protocol regarding how request and response are
interpreted. Blkif.h (and netif.h FWIW) has section to describe xenbus
protocol.

Wei.

> -- 
> Regards,
> -Bob

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