Re: [Xen-devel] test report for Xen 4.3 RC1

["Ren, Yongjie" <yongjie.ren@xxxxxxxxx>]

> -----Original Message-----
> From: Konrad Rzeszutek Wilk [mailto:konrad.wilk@xxxxxxxxxx]
> Sent: Saturday, June 22, 2013 2:18 AM
> To: Ren, Yongjie
> Cc: george.dunlap@xxxxxxxxxxxxx; Xu, YongweiX; Liu, SongtaoX; Tian,
> Yongxue; xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] test report for Xen 4.3 RC1
> 
> > >
> http://bugzilla-archived.xenproject.org//bugzilla/show_bug.cgi?id=1851
> > > > > > > > >
> > > > > > > > > That looks like you are hitting the udev race.
> > > > > > > > >
> > > > > > > > > Could you verify that these patches:
> > > > > > > > > https://lkml.org/lkml/2013/5/13/520
> > > > > > > > >
> > > > > > > > > fix the issue (They are destined for v3.11)
> > > > > > > > >
> > > > > > > > Not tried yet. I'll update it to you later.
> > > > > > >
> > > > > > > Thanks!
> > > > > > > >
> > > > > > We tested kernel 3.9.3 with the 2 patches you mentioned, and
> found
> > > this
> > > > > > bug still exist. For example, we did CPU online-offline for Dom0 for
> > > 100
> > > > > times,
> > > > > > and found 2 times (of 100 times) failed.
> > > > >
> > > > > Hm, does it fail b/c udev can't online the sysfs entry?
> > > > >
> > > > I think no.
> > > > When it fails to online CPU #3 (trying online #1~#3), it doesn't show
> any
> > > info
> > > > about CPU #3 via the output of "devadm monitor --env" CMD. It does
> > > show
> > > > info about #1 and #2 which are onlined succefully.
> > >
> > > And if you re-trigger the the 'xl vcpu-set' it eventually comes back up
> right?
> > >
> > We don't use 'xl vcpu-set' command when doing the CPU hot-plug.
> > We just call the xc_cpu_online/offline() in tools/libxc/xc_cpu_hotplug.c to
> test.
> 
> Oh. That is very different than what I thought. You are not offlining/onlining
> vCPUS - you offlining/onlining pCPUS! So Xen has to cramp the dom0 vCPUs
> in the
> remaining vCPUS.
> 
> There should be no vCPU re-sizing correct?
> 
Yes, for this case we do online/offline for pCPUs not vCPUs.
(vCPU number doesn't change.)

> > (see the attachment about my test code in that bugzilla.)
> > And, yes, if a CPU failed to online, it can also be onlined again when we
> re-trigger
> > online function.
> >
> > > >


> > > > > > > > > > 4. 'xl vcpu-set' can't decrease the vCPU number of a HVM
> > > guest
> > > > > > > > > >   http://bugzilla.xen.org/bugzilla/show_bug.cgi?id=1822
> > > > > > > > >
> > > > > > > > > That I believe was an QEMU bug:
> > > > > > > > >
> > > > >
> http://lists.xen.org/archives/html/xen-devel/2013-05/msg01054.html
> > > > > > > > >
> > > > > > > > > which should be in QEMU traditional now (05-21 was when it
> > > went
> > > > > > > > > in the tree)
> > > > > > > > >
> > > > > > > > In this year or past year, this bug always exists (at least in 
> > > > > > > > our
> > > > > testing).
> > > > > > > > 'xl vcpu-set' can't decrease the vCPU number of a HVM guest
> > > > > > >
> > > > > > > Could you retry with Xen 4.3 please?
> > > > > > >
> > > > > > With Xen 4.3 & Linux:3.10.0-rc3, I can't decrease the vCPU
> number of
> > > a
> > > > > guest.
> > > > >
> > > > sorry, when I said this message, I still use rhel6.4 kernel as the 
> > > > guest.
> > > > After upgrading guest kernel to 3.10.0-rc3, the result became better.
> > > > Basically vCPU increment/decrement can work fine. I'll close that
> bug.
> > >
> > > Excellent!
> > > > But there's still a minor issue as following.
> > > > After booting guest with 'vcpus=4' and 'maxvcpus=32', change its
> vCPU
> > > number.
> > > > # xl vcpu-set $domID 32
> > > > then you can only get less than 32 (e.g. 19) CPUs in the guest; again,
> you
> > > set
> > > > vCPU number to 32 (from 19), then it works to get 32vCPU for the
> guest.
> > > > but 'xl vcpu-set $domID 8' can work fine as we expected.
> > > > vCPU decrement has the same result.
> > > > Can you also have a try to reproduce my issue?
> > >
> > This issue doesn't exist when using the latest QEMU traditional tree.
> > My pervious QEMU was old (March 2013), and I found some of your
> patches
> > were applied in May 2013. These fixes can fix the issue we reported.
> > Close this bug.
> 
> Yes!
> >
> > But, it introduced another issue: when doing 'xl vcpu-set' for HVM
> several
> > times (e.g. 5 times), the guest will panic. Log is attached.
> > Before your patches in qemu traditional tree in May 2013, we never
> meet
> > guest kernel panic.
> > dom0: 3.10.0-rc3
> > Xen: 4.3.0-RCx
> > QEMU: the latest traditional tree
> > guest kernel: 3.10.0-RC3
> > I'll file another bug to track this bug ?
> 
> Please.
> > Can you reproduce this ?
> 
> Could you tell me how you are doing 'xl vcpu-set'? Is there a particular
> test script you are using?
> 
1. xl vcpu-set $domID 2
2. xl vcpu-set $domID 20
3. repeat step #1 and #2 for several times.  (guest kernel panic ...)

I also filed a bug in bugzilla to track this. 
You can get more info in the following link.
http://bugzilla.xenproject.org/bugzilla/show_bug.cgi?id=1860

--
  Jay


> >
> > > Sure. Now how many PCPUS do you have? And what version of QEMU
> > > traditional
> > > were you using?
> > >
> > There're 32 pCPU in that system we used.
> >
> > Best Regards,
> >      Yongjie (Jay)
> 


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