[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
@edison, if you want to push such a patch, please do it through upstream, since it is actually a new feature. I'm going to mark this 'wontfix' (as I thought I had done before), rather than invalid, though the latter still sounds accurate as well. ** Changed in: qemu-kvm (Ubuntu) Status: Confirmed = Won't Fix -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
I had posted a patch to fix the issue before:(http://patchwork.ozlabs.org/patch/64346/), saving memory state is time consuming, which may takes several minutes. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
In qemu 0.14 cache=writeback and cache=none are expected to perform well. The default cache=writethrough is a very conservative setting which is slow by design. I'm pretty sure that it has always been slow, even before 0.12.5. I think that the specific problem with savevm may be related to the VM state being saved in too small chunks. With cache=writethrough this will hurt most. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
The current upstream qemu.git from git://git.savannah.nongnu.org/qemu.git also has the slow savevm. However, it's loadvm takes only a few seconds. ** Also affects: qemu Importance: Undecided Status: New -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
savevm _is_ slow, because it's writing to a qcow2 file with full (meta)data allocation which is terrible slow since 0.13 (and 0.12.5) unless you use cache=unsafe. It's the same slowdown as observed with default cache mode when performing an operating system install into a freshly created qcow2 - it may take several hours. To verify, run `iostat -dkx 5' and see how busy (the last column) your disk is during the save - I suspect it'll be about 100%. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
Confirmed that doing kvm -drive file=lucid.img,cache=unsafe,index=0,boot=on -m 512M -smp 2 -vnc :1 -monitor stdio and doing 'savevm savevm5' takes about 2 seconds. So, for fast savevm, 'cache=unsafe' is the workaround. Shoudl this bug then be marked invalid, or 'wontfix'? -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
I confirm that without 'cache' option, I have got from iostat those result while doing 'savevm' Device: sda rrqm/s: 0.00 wrqm/s: 316.00 r/s: 0.00 w/s: 94.80 rkB/s: 0.00 wkB/s: 1541.60 avgrq-sz: 32.52 avgqu-sz: 0.98 await: 10.32 svctm: 10.10 %util: 95.76 I also confirm, that when option 'cache=unsafe' is used, snapshot (from qemu monitor) is done as quickly as it should (few seconds). I am not sure if this is a solution or workaround or just a closer description of a bug. http://libvirt.org/formatdomain.html#elementsDisks describes option 'cache'. When I use that (cache=none) it spits out: error: Failed to create domain from vm.xml error: internal error process exited while connecting to monitor: kvm: -drive file=/home/dum8d0g/vms/deb.qcow2,if=none,id=drive-ide0-0-0,boot=on,format=qcow2,cache=none: could not open disk image /home/dum8d0g/vms/deb.qcow2: Invalid argument When that option is removed, domain is created successfuly. I guess I have another bugreport to fill. So, for me, the issue is somehow solved from the qemu side. I think, this could be marked as wontfix. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
** Attachment added: used virsh domain XML definition https://bugs.launchpad.net/bugs/741887/+attachment/1937063/+files/vm.xml ** Description changed: Action == # time virsh snapshot-create 1 * Taking snapshot of a running KVM virtual machine Result == Domain snapshot 1300983161 created real4m46.994s user0m0.000s sys 0m0.010s Expected result === * Snapshot taken after few seconds instead of minutes. Environment === * Ubuntu Natty Narwhal upgraded from Lucid and Meerkat, fully updated. * Stock natty packages of libvirt and qemu installed (libvirt-bin 0.8.8-1ubuntu5; libvirt0 0.8.8-1ubuntu5; qemu-common 0.14.0+noroms- 0ubuntu3; qemu-kvm 0.14.0+noroms-0ubuntu3). * Virtual machine disk format is qcow2 (debian 5 installed) image: /storage/debian.qcow2 file format: qcow2 virtual size: 10G (10737418240 bytes) disk size: 1.2G cluster_size: 65536 Snapshot list: IDTAG VM SIZEDATE VM CLOCK 1 snap01 48M 2011-03-24 09:46:33 00:00:58.899 2 1300979368 58M 2011-03-24 11:09:28 00:01:03.589 3 1300983161 57M 2011-03-24 12:12:41 00:00:51.905 * qcow2 disk is stored on ext4 filesystem, without RAID or LVM or any special setup. * running guest VM takes about 40M RAM from inside, from outside 576M are given to that machine * host has fast dual-core pentium cpu with virtualization support, around 8G of RAM and 7200rpm harddrive (dd from urandom to file gives about 20M/s) * running processes: sshd, atd (empty), crond (empty), libvirtd, tmux, bash, rsyslogd, upstart-socket-bridge, udevd, dnsmasq, iotop (python) * networking is done by bridging and bonding Detail description == * Under root, command 'virsh create-snapshot 1' is issued on booted and running KVM machine with debian inside. * After about four minutes, the process is done. * 'iotop' shows two 'kvm' processes reading/writing to disk. First one has IO around 1500 K/s, second one has around 400 K/s. That takes about three minutes. Then first process grabs about 3 M/s of IO and suddenly dissapears (1-2 sec). Then second process does about 7.5 M/s of IO for around a 1-2 minutes. * Snapshot is successfuly created and is usable for reverting or extracting. * Pretty much the same behaviour occurs when command 'savevm' is issued - directly from qemu monitor, without using - libvirf44bfb7fb978c9313ce050a1c4149bf04aa0a670t at all (actually, virsh - snapshot-create just calls 'savevm' to the monitor socket). + directly from qemu monitor, without using libvirt at all (actually, + virsh snapshot-create just calls 'savevm' to the monitor socket). * This behaviour was observed on lucid, meerkat, natty and even with git version of libvirt (f44bfb7fb978c9313ce050a1c4149bf04aa0a670). Also slowsave packages from https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/524447 gave this issue. Thank you for helping to solve this issue! ProblemType: Bug DistroRelease: Ubuntu 11.04 Package: libvirt-bin 0.8.8-1ubuntu5 ProcVersionSignature: Ubuntu 2.6.38-7.38-server 2.6.38 Uname: Linux 2.6.38-7-server x86_64 Architecture: amd64 Date: Thu Mar 24 12:19:41 2011 InstallationMedia: Ubuntu-Server 10.04.2 LTS Lucid Lynx - Release amd64 (20110211.1) ProcEnviron: LANG=en_US.UTF-8 SHELL=/bin/bash SourcePackage: libvirt UpgradeStatus: No upgrade log present (probably fresh install) ** Tags added: kvm libvirt qcow2 qemu savevm snapshot virsh ** Tags removed: apport-bug -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to libvirt in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
** Changed in: libvirt (Ubuntu) Status: New = Confirmed ** Changed in: libvirt (Ubuntu) Importance: Undecided = Medium ** Package changed: libvirt (Ubuntu) = qemu-kvm (Ubuntu) -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
[Bug 741887] Re: virsh snapshot-create too slow (kvm, qcow2, savevm)
Yup, I can definately reproduce this. -- You received this bug notification because you are a member of Ubuntu Server Team, which is subscribed to qemu-kvm in Ubuntu. https://bugs.launchpad.net/bugs/741887 Title: virsh snapshot-create too slow (kvm, qcow2, savevm) -- Ubuntu-server-bugs mailing list Ubuntu-server-bugs@lists.ubuntu.com Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-server-bugs
