Andreas Färber
2013-Jul-26 10:02 UTC
Re: [Qemu-devel] Cirrus VGA slow screen update, show blank screen last 13s or so for windows XP guest
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. (And 1.5 switched the default GUI backend from SDL to GTK, which may again show some performance differences.) 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