Andreas Färber
2013-Jul-26 10:27 UTC
Re: [Qemu-devel] Cirrus VGA slow screen update, show blank screen last 13s or so for windows XP guest
Am 26.07.2013 12:19, schrieb Gerd Hoffmann:> On 07/26/13 12:02, Andreas Färber 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 screen >>>> last 13s or so for windows XP guest >>>> >>>> On Thu, Jul 25, 2013 at 10:08 PM, Gonglei (Arei) >>>> <arei.gonglei@huawei.com> wrote: >>>>> 3. Why does the traditional qemu has no blank screen problem on cirrus 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 >>> but the upstream qemu(begin with qemu-0.14) is not for the >>> same windows XP guest image in cirrus vga emulation. Does >>> the cirrus vga emulation have some differences between >>> qemu-dm and unstream qemu ? >> >> 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 != 1.4 ;)Oops! In that case, Gonglei, try to reproduce the issue with upstream 0.10 and use git-bisect to find out when things got slower between v0.10.2..v0.14.0. It would be unrealistic to expect us to remember all Cirrus-related changes from 2-4 years ago. ;) Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel