qemu-kvm, virtual network stalling under load
Hi, i have this problem with every network model and also using the newest release 0.12.3, which states that this problem is fixed for virtio-net :-/
host system is slackware64 13.0, guest too! kernel 126.96.36.199 on qemu-kvm-0.12.3
network is bridged using tap and virtio (copy performance around 60MB/s until stall :-(
copying large files via scp from the host to vm's /dev/null works! but copying e.g. the slackware-installiso from a mounted nfs share stalls the network of the virtual machine completely!!
also transfering a few hundret megs via ftp/ftps stalls the network completely!
no network response from the vm (ssh, icmp, etc..)
i can only shutdown and restart the vm using qemu monitor since i am running headless servers!
when using another NIC model the amount of transferable data decreases to only a few megs untill the network stalls :-/
error logs simply say nothing that indcate the problem :-/
anyone some hints or a possible solution for this defect?
How did you configure your VMs? I mean, how's your kvm command/script built?
I use raw files for my VMs and separate loopback files for /home partitions. Keeps files sizes more manageable. All the drives are ext3 for stability and recovery.
qemu command in a script of course:
qemu-system-x86_64 -cpu qemu64,+ssse3,+ht,+monitor,+vmx,+est,+cx16,+xtpr
-monitor $MONITOR 1>$LOGFILE 2>$ERRORFILE &
MEM is between 1 and 4 GB depending on the server (there are actually 6 of them running, more to come)
it just locks up under heavy load resp. after some datatransfer oder the virtual network via nfs... (this happens regardless if there where 1 or more servers running)
case study 100% reproducable:
- using virtio i can -> update slackware with all current patches, but i cannot dump or copy the slackware iso from the nfs mount. i CAN copy the iso via scp although!
- using virtio and changing the rsize/wsize to 1MB increases virtual network speed from 60MB/s to 124MB/s and lets me dump/copy the iso sometimes...
- using another nic model (e.g. one of the intel or rtl) i cannot even upgrade slackware! network stalls when transferring the gimp package!
- i changed the kernel to 188.8.131.52. now i can dump/copy the iso some more times, but not always! but the network still stalls when i try to dump/copy a urandom created 50gig image! so switching the kernel did not fix the bug...
i'm running out of ideas, and i don't want to switch my hypervisor to virtualbox or vmware, simply because of their limitations and performance, i really like kvm :-( PLZ HELP!! :-)
btw: what exactly is the difference of kvm88 and qemu-kvm-devel-88 and qemu-kvm-0.12.3 (the first two state to be development branch, the last states to be the stable but is the newest!?) i don't understand their release management!?
i am using qemu-kvm-0.12.3 on a tyan server mobo with 2x quadcore xeon w. hyperthreading and 24GB ram... i run 64bit host and guests to get the most perfmormance out of my virtual server environment! all machines are powered by a raid5 + lvm using xfs... (this is just to give you a impression of the environment i deal with)
i hope there is a solution out there somewhere, but the replys on qemu and kvm forums are NULL... :-(
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