Re: [Qemu-devel] Windows slow boot: contractor wanted

[Benoît Canet]

Le Thursday 16 Aug 2012 à 11:47:27 (+0100), Richard Davies a écrit :
> Hi,
> 
> We run a cloud hosting provider using qemu-kvm 1.1, and are keen to find a
> contractor to track down and fix problems we have with large memory Windows
> guests booting very slowly - they can take several hours.
> 
> We previously reported these problems in July (copied below) and they are
> still present with Linux kernel 3.5.1 and qemu-kvm 1.1.1.
> 
> This is a serious issue for us which is causing significant pain to our
> larger Windows VM customers when their servers are offline for many hours
> during boot.
> 
> If anyone knowledgeable in the area would be interested in being paid to
> work on this, or if you know someone who might be, I would be delighted to
> hear from you.
> 
> Cheers,
> 
> Richard.
> 
> 
> ===== Previous bug report
> 
> http://marc.info/?l=qemu-devel&m=134304194329745
> 
> 
> We have been experiencing this problem for a while now too, using qemu-kvm
> (currently at 1.1.1).
> 
> Unfortunately, hv_relaxed doesn't seem to fix it. The following command line
> produces the issue:
> 
> qemu-kvm -nodefaults -m 4096 -smp 8 -cpu host,hv_relaxed -vga cirrus 
> -usbdevice tablet -vnc :99 -monitor stdio -hda test.img
> 
> The hardware consists of dual AMD Opteron 6128 processors (16 cores in
> total) and 64GB of memory. This command line was tested on kernel 3.1.4. 
> 
> I've also tested with -no-hpet.
> 
> What I have seen is much as described: the memory fills out slowly, and top
> on the host will show the process using 100% on all allocated CPU cores. The
> most extreme case was a machine which took something between 6 and 8 hours
> to boot.
> 
> This seems to be related to the assigned memory, as described, but also the
> number of processor cores (which makes sense if we believe it's a timing
> issue?). I have seen slow-booting guests improved by switching down to a
> single or even two cores.
> 
> Matthew, I agree that this seems to be linked to the number of VMs running -
> in fact, shutting down other VMs on a dedicated test host caused the machine
> to start booting at a normal speed (with no reboot required).
> 
> However, the level of contention is never such that this could be explained
> by the host simply being overcommitted.
> 
> If it helps anyone, there's an image of the hard drive I've been using to
> test at:
> 
> http://46.20.114.253/
> 
> It's 5G of gzip file containing a fairly standard Windows 2008 trial
> installation. Since it's in the trial period, anyone who wants to use it may
> have to re-arm the trial: http://support.microsoft.com/kb/948472
> 
> Please let me know if I can provide any more information, or test anything.

For info the image boot pretty fast with qemu-kvm 1.1.1 and a 3.2.0-29 ubuntu 
kernel
on a core i7 with these parameters.

Benoît

> 
> Best wishes,
> 
> Owen Tuz
>