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 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
