From mboxrd@z Thu Jan  1 00:00:00 1970
From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Subject: Re: [PATCH] xenbus_client: extend interface to suppurt
 multi-page ring
Date: Tue, 27 Aug 2013 10:12:07 -0400
Message-ID: <20130827141207.GE3725@phenom.dumpdata.com>
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To: Wei Liu <wei.liu2@citrix.com>
Cc: boris.ostrovsky@oracle.com, xen-devel@lists.xen.org, Ian Campbell <Ian.Campbell@citrix.com>, david.vrabel@citrix.com
List-Id: xen-devel@lists.xenproject.org

On Tue, Aug 27, 2013 at 09:25:42AM +0100, Wei Liu wrote:
> On Tue, Aug 27, 2013 at 09:23:24AM +0100, Ian Campbell wrote:
> > On Fri, 2013-08-23 at 23:27 +0100, Wei Liu wrote:
> > > Originally Xen PV drivers only use single-page ring to pass along
> > > information. This might limit the throughput between frontend and
> > > backend.
> > > 
> > > The patch extends Xenbus driver to support multi-page ring, which in
> > > general should improve throughput if ring is the bottleneck. Changes to
> > > various frontend / backend to adapt to the new interface are also
> > > included.
> > 
> > The changes to the front/backends here simply adapt to the new interface
> > but don't actually make use of it, right?
> > 
> 
> No, they don't.

I think the scsi front or usb front (in a different branch) did use it.
That is why I remember seeing something similar to this.

Either way, I am comfortable putting this in - will make it easier for
folks to experiement with enlarging the ring.
> 
> > > @@ -196,15 +200,18 @@ int xenbus_watch_pathfmt(struct xenbus_device *dev, struct xenbus_watch *watch,
> > >  			 const char *pathfmt, ...);
> > >  
> > >  int xenbus_switch_state(struct xenbus_device *dev, enum xenbus_state new_state);
> > > -int xenbus_grant_ring(struct xenbus_device *dev, unsigned long ring_mfn);
> > > -int xenbus_map_ring_valloc(struct xenbus_device *dev,
> > > -			   int gnt_ref, void **vaddr);
> > > -int xenbus_map_ring(struct xenbus_device *dev, int gnt_ref,
> > > -			   grant_handle_t *handle, void *vaddr);
> > > +int xenbus_grant_ring(struct xenbus_device *dev, void *vaddr,
> > > +		      unsigned int nr_pages, grant_ref_t *grefs);
> > > +int xenbus_map_ring_valloc(struct xenbus_device *dev, grant_ref_t *gnt_refs,
> > > +			   unsigned int nr_grefs, void **vaddr);
> > 
> > In the definition nr_grefs is called grefs_order. From the usage I think
> > the definition and not this prototype is correct.
> > 
> 
> Good catch, thanks.
> 
> Wei.
> 
> > Ian.
> 
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