From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1KcM9r-0008CV-KI
	for qemu-devel@nongnu.org; Sun, 07 Sep 2008 11:26:35 -0400
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1KcM9m-000825-R0
	for qemu-devel@nongnu.org; Sun, 07 Sep 2008 11:26:35 -0400
Received: from [199.232.76.173] (port=44228 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1KcM9m-00081q-IG
	for qemu-devel@nongnu.org; Sun, 07 Sep 2008 11:26:30 -0400
Received: from toccata.ens-lyon.org ([140.77.166.68]:42583)
	by monty-python.gnu.org with esmtps
	(TLS-1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.60)
	(envelope-from <samuel.thibault@labri.fr>) id 1KcM9m-0001vI-7e
	for qemu-devel@nongnu.org; Sun, 07 Sep 2008 11:26:30 -0400
Date: Sun, 7 Sep 2008 17:12:54 +0200
From: Samuel Thibault <samuel.thibault@ens-lyon.org>
Subject: Re: [Qemu-devel] [PATCH] opengl rendering in the sdl window
Message-ID: <20080907151254.GP4307@implementation>
References: <48B81423.9050502@eu.citrix.com>
	<200809071536.51498.paul@codesourcery.com>
	<20080907144221.GN4307@implementation>
	<200809071603.31181.paul@codesourcery.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
In-Reply-To: <200809071603.31181.paul@codesourcery.com>
Content-Transfer-Encoding: quoted-printable
Reply-To: qemu-devel@nongnu.org
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: Paul Brook <paul@codesourcery.com>
Cc: qemu-devel@nongnu.org

Paul Brook, le Sun 07 Sep 2008 16:03:30 +0100, a =E9crit :
> On Sunday 07 September 2008, Samuel Thibault wrote:
> > Paul Brook, le Sun 07 Sep 2008 15:36:51 +0100, a =E9crit :
> > > > Ideally, once switched to fullscreen you could just let the guest
> > > > directly write to the actual video memory (particularly interesti=
ng for
> > > > Xen and KVM).
> > >
> > > You really don't want to have the guest writing directly to host vi=
deo
> > > ram. Video ram tends to be high-latency, so you want to write to re=
gular
> > > memory, then use a wide block transfer or DMA to copy to video ram.
> >
> > How often? =20
>=20
> You probably want to sync the updates to the vertical refresh. Updating=
 more=20
> often than that is pointless.

Sure.

> > Which part(s) of the framebuffer?=20
>=20
> Whichever parts have changed.

Sure, how do you detect that?
The previous Xen memcmp method was eating 10% cpu for a 30Hz refresh,
just for the memcmp.  Now it uses the pagetable dirty bits and after
some idleness, trapping, but having the guest just write to actual
video memory (when it _has_ to be shown on the screen anyway) seems the
fastest way.

Samuel