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

[George Dunlap <george.dunlap@eu.citrix.com>]

On 17/01/13 20:57, Pasi Kärkkäinen wrote:
> Hello,
>
> George: What do you think, should we add this bug to the Xen 4.3 status email for tracking it?
> It's a serious HVM/winxp performance regression on AMD..

Hey Pasi -- thanks for bringing this thread to my attention.  I had 
noticed a performance impact on AMD boxen myself, but investigating it 
had kind of gotten buried in more urgent tasks.  Yes, I think we should 
track it.  I'll put it on the list.

  -George

>
> -- Pasi
>
> On Sat, Jan 12, 2013 at 04:25:47PM +0100, Peter Maloney 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@xen.org> 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@lagarcavilla.org>
>>>>>>>> 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?
>>
>>
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