Re: [Qemu-devel] [PATCH] kvm: flush the dirty log when unregistering a slot

[Gerhard Wiesinger <lists@wiesinger.com>]

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.c
We 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

--
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