Re: [Xen-devel] VMX status report. Xen: #17270 & Xen0: #488 -- nonew issue

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 26/3/08 10:00, "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx> wrote:

>> Keir, we checked guest installation with rhel4u3 today, we compared c/s
>> 17284 with c/s 16720,
>> The result shows latest c/s with mmio emulation changes is a little bit
>> faster than before on our test system with Xeon(r) processors, about 20
>> seconds faster.
> 
> That's pretty surprising! I found out that slowdown on my P4 system for
> WinXP installation is about 15%, so not as bad as I thought. And I can
> probably reclaim most of that performance loss.
> 
> I find it hard to explain a performance *win* though!

Well, I implemented a virtual-address to mmio-physical-address lookaside
cache for x86_emulate(), and with that I get following results for install
of WinXP (time is up to second reboot, after graphical part of install, from
an auto-install CD image):
 xen 3.2: 1 hour 20 minutes 23 seconds
 xen unstable using x86_emulate(): 1 hour 33 minutes 4 seconds
 xen unstable with new optimisation: 1 hour 12 minutes 57 seconds

Considering first result (Xen 3.2) as a baseline control experiment, basic
x86_emulate() mmio performance is 16% slower, while with the simple extra
optimisation I get a 10% speedup (so that's 22% speedup compared without the
optimisation).

Pretty nice!

 -- Keir



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