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Re: [Xen-devel] xen-unstable, winxp32 very poor performance on AMD FX-8150, I bisected and changeset is 24770:7f79475d3de7

On Sat, Jan 12, 2013 at 3:25 PM, Peter Maloney <peter.maloney@xxxxxxxxxxxxxxxxxxxx> wrote:
On 11/22/2012 07:54 PM, Peter Maloney wrote:
> On 11/13/2012 02:17 PM, Peter Maloney wrote:
>> On 2012-11-01 18:28, Andres Lagar-Cavilla wrote:
>>> On Nov 1, 2012, at 1:00 PM, Tim Deegan <tim@xxxxxxx> wrote:
>>>> Hi,
>>>> At 14:59 +0100 on 22 Oct (1350917960), Tim Deegan wrote:
>>>>> At 19:21 +0200 on 20 Oct (1350760876), Peter Maloney wrote:
>>>>>> The change was 8 months ago
>>>>>> changeset:   24770:7f79475d3de7
>>>>>> user:        Andres Lagar-Cavilla <andres@xxxxxxxxxxxxxxxx>
>>>>>> date:        Fri Feb 10 16:07:07 2012 +0000
>>>>>> summary:     x86/mm: Make p2m lookups fully synchronized wrt modifications
>>>> [...]
>>> Not any immediate ideas without profiling.
>>> However, most callers of hvmemul_do_io pass a stub zero ram_gpa address. We might be madly hitting the p2m locks for no reason there.
>>> How about the following patch, Peter, Tim?
> I tried the patch applied to xen-unstable 4.2.0-branched
> 528f0708b6db+ 4.2.0-branched
> It seemed the same. It was extremely slow with 7 vcpus, and with 2 vcpus
> it was slow, but fast enough that I could bother to log in and out
> during the test.
> Attached are logs generated with this command (using xm instead of xl):
> for i in {1..30}; do xm debug-keys d; xm dmesg -c; done >> nameoflog
> xenxp_xm_dmesg_-c_7cpus_idle.log
> xenxp_xm_dmesg_-c_7cpus_logintooslow.log
> xenxp_xm_dmesg_-c_7cpus_shutdown.log
> xenxp_xm_dmesg_-c_duringlogin.log
> xenxp_xm_dmesg_-c_idling_login_screen.log
> Also there is xenxp_dmesg.log which is output from hitting alt+sysrq+w
> and p in case it's relevant.
> BTW this time I am testing with kernel 3.6.7

I also tested 4.2.1 now, and it has the same problem. And after using it
for a while with windows 8 (playing games), I get the general feel that
it is laggier than with 4.1.3. And now I'm using 4.1.4 which is fast
like 4.1.3.

So any ideas on how to fix this or gather more useful information?


One thing that would be helpful is if we could have a quantifiable difference, other than "feels laggier".  If this is related to the problem I saw a few months ago, running winXP and looking at "top" in qemu is pretty clear.  If you have a bit of time, do you suppose you could try to look around for a freely-available benchmark that would give us some numbers for Windows 8?  That might help us track down the problem better as well.

I've put this on my 4.3 release tracking list, so it should get attention.

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