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[Qemu-discuss] copy of 4G file in qemu fails

From: Roman Mashak
Subject: [Qemu-discuss] copy of 4G file in qemu fails
Date: Mon, 10 Nov 2014 21:41:26 -0500


I use qemu-1.6.2 from ovs-dpdk package available at

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
-mem-path /dev/hugepages -mem-prealloc -monitor
-net none -netdev

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:

(gdb) bt
#0  vhost_net_stop (address@hidden, ncs=0x555556851e40,
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/hw/net/vhost_net.c:251
#1  0x00005555557a8c43 in virtio_net_vhost_status (status=7 '\a',
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/hw/net/virtio-net.c:136
#2  virtio_net_set_status (vdev=<optimized out>, status=<optimized out>)
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/hw/net/virtio-net.c:148
#3  0x00005555557b4cb7 in virtio_set_status (vdev=0x555556858df8,
    val=<optimized out>)
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/hw/virtio/virtio.c:533
#4  0x000055555576433b in vm_state_notify (address@hidden,
    address@hidden) at vl.c:1764
#5  0x000055555576a8da in do_vm_stop (state=RUN_STATE_IO_ERROR)
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/cpus.c:445
#6  vm_stop (address@hidden)
    at /home/rmashak/work/ovs_dpdk_1_1_0/qemu/cpus.c:1119
#7  0x00005555555f4dea in bdrv_error_action (bs=0x55555615a0a0,
    address@hidden, address@hidden,
    address@hidden) at block.c:2805
#8  0x0000555555688e75 in ide_handle_rw_error (address@hidden,
    error=28, op=<optimized out>) at hw/ide/core.c:610
#9  0x00005555556892a7 in ide_dma_cb (opaque=0x55555687bb18,
---Type <return> to continue, or q <return> to quit---
    ret=<optimized out>) at hw/ide/core.c:629
#10 0x000055555562aba1 in dma_complete (dbs=0x7fffe8021490, ret=-28)
    at dma-helpers.c:120
#11 0x000055555562ae2a in dma_bdrv_cb (opaque=0x7fffe8021490, ret=-28)
    at dma-helpers.c:148
#12 0x00005555555ed472 in bdrv_co_em_bh (opaque=0x7fffe803f310) at block.c:3850
#13 0x00005555555e02d7 in aio_bh_poll (address@hidden)
    at async.c:81
#14 0x00005555555dfe58 in aio_poll (ctx=0x55555613ba20,
    address@hidden) at aio-posix.c:185
#15 0x00005555555e0190 in aio_ctx_dispatch (source=<optimized out>,
    callback=<optimized out>, user_data=<optimized out>) at async.c:194
#16 0x00007ffff76f02a6 in g_main_context_dispatch ()
   from /lib64/libglib-2.0.so.0
#17 0x00005555556f549a in glib_pollfds_poll () at main-loop.c:188
#18 os_host_main_loop_wait (timeout=<optimized out>) at main-loop.c:233
#19 main_loop_wait (nonblocking=<optimized out>) at main-loop.c:465
#20 0x00005555555db710 in main_loop () at vl.c:2089
#21 main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>)
    at vl.c:4431

It looks that an error has occurred during disk I/O (frame 8) and it
resulted in subsequent VM stop.

Is this a known issue? Can disk I/O be tuned to avoid such behaviour
during copying of large files?


Roman Mashak

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