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From: | Gerhard Wiesinger |
Subject: | Re: [Qemu-devel] [PATCH] kvm: flush the dirty log when unregistering a slot |
Date: | Fri, 27 Jan 2012 07:50:10 +0100 (CET) |
User-agent: | Alpine 2.02 (LFD 1266 2009-07-14) |
On Thu, 26 Jan 2012, Avi Kivity wrote:
On 01/25/2012 10:15 PM, Gerhard Wiesinger wrote:On Sun, 15 Jan 2012, Avi Kivity wrote:On 01/15/2012 04:40 PM, Gerhard Wiesinger wrote:On Sun, 15 Jan 2012, Jan Kiszka wrote:On 2012-01-15 15:17, Avi Kivity wrote:Otherwise, the dirty log information is lost in the kernel forever. Fixes opensuse-12.1 boot screen, which changes the vga windows rapidly.Confirmed, problems solved here.Problem from: http://permalink.gmane.org/gmane.comp.emulators.qemu/131853 Confirmed to be fixed, too. Long awaited patch :-)Sorry, I forgot about that. Please ping me if I do that.BTW: There is also a major difference in video performance: 1.) With Patch: 1400MB/s (MByte/s) 2.) Without Patch: 6MB/s Any reason for that?What are you measuring exactly?I'm measuring VGA video performance under DOS with own written test program. What's strange, new findings: Measurement doesn't depend on the patch. Sometimes it is high sometimes low. I think I have to investigate further. Any ideas?What vga mode are you using? What does the test program do?
DOS Test programs, source and binaries can be found at: http://www.wiesinger.com/opensource/qemu/ 1.) Measures page A000:0000 with videomode 4F02, see: http://www.wiesinger.com/opensource/qemu/memperf.c 2.) Second test program measures setting and getting video bank, see: http://www.wiesinger.com/opensource/qemu/int10per.cWe already talked about the low performance some time ago and tracked it down to kernel <=> userspace switching. But I benchmarked it already once and I think there are some optimizations possible (linear list search) with mapping functions (e.g. trivial hash function before)
Thnx. Ciao, Gerhard -- http://www.wiesinger.com/
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