From mboxrd@z Thu Jan 1 00:00:00 1970 From: Dan Magenheimer Subject: RE: Add multi-page shared ring support to xen-blkfront/back Date: Tue, 12 Jan 2010 15:52:00 -0800 (PST) Message-ID: References: <4B4CB6AE.70005@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset=Windows-1252 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <4B4CB6AE.70005@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Paul Durrant , xen-devel@lists.xensource.com List-Id: xen-devel@lists.xenproject.org Haven't read the patch carefully, but a question: Will blkback fall back safely to single-page allocation if fragmentation has occurred... and, if so, will this inability to allocate multi-page be dynamically propogated to blkfronts (rather than just the largest ring size "supported" by blkback)? > -----Original Message----- > From: Paul Durrant [mailto:paul.durrant@citrix.com] > Sent: Tuesday, January 12, 2010 10:52 AM > To: xen-devel@lists.xensource.com > Subject: Re: [Xen-devel] Add multi-page shared ring support to > xen-blkfront/back >=20 >=20 > Paul Durrant wrote: > > These patches add support for multi-page shared rings to=20 > xen-blkfront/back. > > Shared rings must always be a power of 2 in size and so the=20 > size is controlled > > by the new 'max_ring_page_order' module parameter of=20 > xen-blkback. This defaults > > to 0 so operationally there should be no difference with=20 > these patches in place. > > The maximum value of 'max_ring_page_order' is currently limited to 2 > > (i.e. 4 pages). > > xen-blkfront will always use the largest shared ring size=20 > supported by the back > > end. To override this and continue to use a single page=20 > ring, as before, set the > > 'allow_multi_page_ring' module parameter to 0. > >=20 >=20 > I don't know why git-send-email seems to have sent my patch=20 > series into=20 > a black hole. Here they are as attachments this time. >=20 > Paul >=20 > --=20 > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D > Paul Durrant, Software Engineer >=20 > Citrix Systems (R&D) Ltd. > First Floor, Building 101 > Cambridge Science Park > Milton Road > Cambridge CB4 0FY > United Kingdom > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D >