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Re: [Qemu-discuss] Qemu-discuss Digest, Vol 38, Issue 11


From: Markus Stockhausen
Subject: Re: [Qemu-discuss] Qemu-discuss Digest, Vol 38, Issue 11
Date: Tue, 11 Nov 2014 17:30:12 +0000

Hi Roman,

> From: Roman Mashak <address@hidden>
> To: address@hidden
> Subject: [Qemu-discuss] copy of 4G file in qemu fails
> Message-ID:
>         <address@hidden>
> Content-Type: text/plain; charset=UTF-8
> 
> Hello,
> 
> I use qemu-1.6.2 from ovs-dpdk package available at
> https://01.org/sites/default/files/downloads/packet-processing/openvswitchdpdk.l.1.1.0-27.gz
> 
> I start qemu as:
> 
> % sudo qemu-system-x86_64 -cpu host -boot c -hda fedora.qcow2
> -snapshot -m 1024 --enable-kvm -name vm0 -nographic -pidfile
> /usr/local/ovs_dpdk/var/run/vm0.pid
> -mem-path /dev/hugepages -mem-prealloc -monitor
> unix:/usr/local/ovs_dpdk/var/run/vm0monitor,server,nowait
> -net none -netdev
> type=tap,id=net0,script=no,downscript=no,ifname=vhost0,vhost=on
> -device 
> virtio-net-pci,netdev=net0,csum=off,gso=off,guest_tso4=off,guest_tso6=off,guest_ecn=off
> %
> 
> So I can ping from VM through vport and via a physical interface the
> other machine. However running a heavy traffic (scp of 4G binary file
> to VM) drops off the vhost interface:
> 
> % scp address@hidden:/home/user/image.iso .
> ...
> 
> After ~90-91% completed I get this in qemu:
> [   88.198496] perf samples too long (2506 > 2500), lowering
> kernel.perf_event_max_sample_rate to 50000
> [  117.924805] perf samples too long (5060 > 5000), lowering
> kernel.perf_event_max_sample_rate to 25000
> 
> And shortly after in ovs-dpdk console:
> APP: (0) Device has been removed from ovdk_pf port vhost0
> ...
> 
> I connected to running qemu with GDB and found that the qemu sends
> ioctl to stop vhost:
> 
> ...
> It looks that an error has occurred during disk I/O (frame 8) and it
> resulted in subsequent VM stop.

Do you think this is similar behaviour like my (older) bug report:
http://lists.gnu.org/archive/html/qemu-discuss/2014-09/msg00030.html

> Is this a known issue? Can disk I/O be tuned to avoid such behaviour
> during copying of large files?
> 
> Thanks.
> 
> --
> Roman Mashak

Markus

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