W dniu 2015-11-19 o 11:07, Michal Privoznik pisze:
On 18.11.2015 15:33, Piotr Rybicki wrote:
Hi.
There is a mem leak in libvirt, when doing external snapshot (for backup
purposes). My KVM domain uses raw storage images via libgfapi. I'm using
latest 1.2.21 libvirt (although previous versions act the same).
My bash script for snapshot backup uses series of shell commands (virsh
connect to a remote libvirt host):
* virsh domblklist KVM
* qemu-img create -f qcow2 -o backing_file=gluster(...) - precreate
backing file
* virsh snapshot-create KVM SNAP.xml (...) - create snapshot from
precreated XML snapshot file
* cp main img file
* virsh blockcommit KVM disk (...)
Backup script works fine, however libvirtd process gets bigger and
bigger each time I run this script.
Some proof of memleak:
32017 - libvirtd pid
When libvirt started:
# ps p 32017 o vsz,rss
VSZ RSS
585736 15220
When I start KVM via virsh start KVM
# ps p 32017 o vsz,rss
VSZ RSS
1327968 125956
When i start backup script, after snapshot is created (lots of mem
allocated)
# ps p 32017 o vsz,rss
VSZ RSS
3264544 537632
After backup script finished
# ps p 32017 o vsz,rss
VSZ RSS
3715920 644940
When i start backup script for a second time, after snapshot is created
# ps p 32017 o vsz,rss
VSZ RSS
5521424 1056352
And so on, until libvirt spills 'Out of memory' when connecting, ane
being really huge process.
Now, I would like to diagnose it further, to provide detailed
information about memleak. I tried to use valgrind, but unfortunatelly
I'm on Opteron 6380 platform, and valgrind doesn't support XOP quitting
witch SIGILL.
If someone could provide me with detailed information on how to get some
usefull debug info about this memleak, i'll be more than happy to do it,
and share results here.
You can run libvirtd under valgrind (be aware that it will be slow as
snail), then run the reproducer and then just terminate the daemon
(CTRL+C). Valgrind will then report on all the leaks. When doing this I
usually use:
# valgrind --leak-check=full --show-reachable=yes \
--child-silent-after-fork=yes libvirtd
Remember to terminate the system-wide daemon firstly as the one started
under valgrind will die early since you can only have one deamon running
at the time.
If you are unfamiliar with the output, share it somewhere and I will
take a look.
Thank You Michal.
I finally managed to have valgrind running on Opteron 6380. I recomplied
with -mno-xop glibc, libvirt and other revelant libs (just for others
looking for solution for valgrind on Opteron).
Gluster is at 3.5.4
procedure is:
start libvirtd
start kvm
run backup script (with external snapshot)
stop kvm
stop libvirtd
Valgrind output:
http://wikisend.com/download/457046/valgrind.log
I' happy to test patches against libvirt 1.2.21 and retest.
Best regards
Piotr Rybicki
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