Re: [Xen-users] Poor Windows 2003 + GPLPV performance compared to VMWare

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-09-18 at 14:06 +0100, Adam Goryachev wrote:
> On 15/09/12 00:53, Adam Goryachev wrote:
> > On 14/09/12 23:30, Ian Campbell wrote:
> >
> >>>>> device_model    = '/usr/lib/xen-default/bin/qemu-dm'
> >>>>> localtime    = 1
> >>>>> name        = "vm1"
> >>>>> cpus        = "2,3,4,5"    # Which physical CPU's to allow
> >>>> Have you pinned dom0 to use pCPU 1 and/p pCPUs > 6?
> >>> No, how should I pin dom0 to cpu0 ?
> >> dom0_vcpus_pin as described in
> >> http://xenbits.xen.org/docs/4.2-testing/misc/xen-command-line.html
> > Thanks, I'll need to reboot the dom0 to apply this, will do as soon as
> > this current scheduled task is complete.
> OK, I have pinned dom0 to cpu0, and this had no effect on performance.
> >> You have:
> >>         cpus = "2,3,4,5"
> >> which means "let all the guests VCPUs run on any of PCPUS 2-5".
> >>
> >> It sounds like what you are asking for above is:
> >>         cpus = [2,3,4,5]
> >> Which forces guest vcpu0=>pcpu=2, 1=>3, 2=>4 and 3=>5.
> >>
> >> Subtle I agree.
> > Ugh... ok, I'll give that a try. BTW, it would seem this is different
> > from xen 4.0 (from debian stable) where it seems to magically do what I
> > meant to say, or I'm just lucky on those machines :)
> Actually, the above syntax doesn't work:
> cpus        = [2,3,4,5]    # Which physical CPU's to allow
> Error: 'int' object has no attribute 'split'

Is it ["2","3"...] then I wonder?

> Once I reverted to:
> cpus    = "2,3,4,5"
> I can then boot again, but on reboot I get this:
> xm vcpu-list
> Name                                ID  VCPU   CPU State   Time(s) CPU
> Affinity
> Domain-0                             0     0     0   r--     148.9 0
> cobweb                               6     0     5   ---       0.5 2-5
> cobweb                               6     1     -   --p       0.0 2-5
> cobweb                               6     2     -   --p       0.0 2-5
> cobweb                               6     3     -   --p       0.0 2-5
> 
> So it isn't pinning each vcpu to a specific cpu... but I suppose it
> should be smart enough to do it well anyway...
> Performance is still at the same level.

To be honest I wouldn't expect it to make much difference at this stage.

I notice the state is "--p" for all but VCPU0 -- which means they are
paused.

It's probably just that you ran the xm vcpu-list before Windows booted
as far as brining up secondary CPUs but it would be worth checking that
Windows is actually bringing up / using all the CPUs!

Once the VM is fully booted then the state for each vcpu should either
be "r--" (running) or "-b-" (currently blocked). I presume something
like Windows task manager will also confirm that all the CPUs are in
use.

> I'm really at a bit of a loss on where to go from here.... The standard
> performance improvements don't seem to make any difference at all, and
> I'm running out of ideas....
> 
> Could you suggest a "standard" tool which would allow me to test disk IO
> performance (this is my initial suspicion for slow performance), and
> also CPU performance (I'm starting to suspect this too now) in both
> windows (domU), linux (domU I can create one for testing) and Linux
> (dom0). Then I can see where performance is lost (CPU/disk) and at what
> layer (dom0/domU) etc...

Fajar's suggestion of fio is a good one.

Ian.


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