From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36505) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V2f7Q-0005H5-77 for qemu-devel@nongnu.org; Fri, 26 Jul 2013 06:19:29 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V2f7N-0004Iy-4v for qemu-devel@nongnu.org; Fri, 26 Jul 2013 06:19:28 -0400 Received: from mx1.redhat.com ([209.132.183.28]:56184) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V2f7M-0004Im-Rt for qemu-devel@nongnu.org; Fri, 26 Jul 2013 06:19:25 -0400 Message-ID: <51F24D24.4020201@redhat.com> Date: Fri, 26 Jul 2013 12:19:16 +0200 From: Gerd Hoffmann MIME-Version: 1.0 References: <33183CC9F5247A488A2544077AF190207EF6A7E6@szxeml538-mbx.china.huawei.com> <33183CC9F5247A488A2544077AF190207EF6BEC3@szxeml538-mbx.china.huawei.com> <33183CC9F5247A488A2544077AF190207EF6BF06@szxeml538-mbx.china.huawei.com> <51F24949.4070109@suse.de> In-Reply-To: <51F24949.4070109@suse.de> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] Cirrus VGA slow screen update, show blank screen last 13s or so for windows XP guest List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= Cc: Hanweidong , Luonengjun , "qemu-devel@nongnu.org" , "xen-devel@lists.xen.org" , "Gonglei (Arei)" , Anthony Liguori , "Huangweidong (Hardware)" On 07/26/13 12:02, Andreas F=C3=A4rber wrote: > Am 26.07.2013 08:41, schrieb Gonglei (Arei): >>> -----Original Message----- >>> From: Anthony Liguori [mailto:anthony@codemonkey.ws] >>> Sent: Friday, July 26, 2013 11:21 AM >>> To: Gonglei (Arei) >>> Cc: qemu-devel@nongnu.org; xen-devel@lists.xen.org; Hanweidong; >>> Luonengjun; Huangweidong (Hardware) >>> Subject: Re: [Qemu-devel] Cirrus VGA slow screen update, show blank s= creen >>> last 13s or so for windows XP guest >>> >>> On Thu, Jul 25, 2013 at 10:08 PM, Gonglei (Arei) >>> wrote: >>>> 3. Why does the traditional qemu has no blank screen problem on cirr= us VGA >>> emulation ? >>> >>> This is one of the few cases where TCG is actually faster than KVM or >>> Xen. In TCG, an MMIO exit is converted to a function call. OTOH, >>> even with KVM, an MMIO exit is at least a couples thousand cycles. >>> It's worse with Xen because dom0 has to be scheduled. >> >> Perhaps I did not express clearly what I mean at #3. >> I don't understand why the qemu-dm(qemu-0.10.2) works well=20 >> but the upstream qemu(begin with qemu-0.14) is not for the=20 >> same windows XP guest image in cirrus vga emulation. Does=20 >> the cirrus vga emulation have some differences between=20 >> qemu-dm and unstream qemu ? >=20 > I don't know about qemu-dm, but QEMU switched from a home-grown pixel > handling to pixman library sometime around 1.4. CC'ing Gerd. 0.14 !=3D 1.4 ;) Also pixman isn't used everywhere, there is still home-grown pixel handling code in qemu. I often replace it when I touch it for some reason, but we are far away from a full-pixman qemu. The cirrus blit ops havn't been touched btw, it's still the old code. Maybe the xen guys did some optimizations in qemu-dm which where not merged upstream. Try asking @ xen-devel. Beside that the standard vga usually is the better choice anyway as it supports more video memory and higher resolutions than cirrus. cheers, Gerd