[Qemu-devel] [Bug 1481272] Re: main-loop: WARNING: I/O thread spun for 1000 iterations

[Bruce Hohl <1481272@bugs.launchpad.net>]

I have experienced this behavior (main-loop: WARNING: I/O thread spun
for 1000 iterations) and the resulting degraded performance.  The VM
becomes very unresponsive but eventually recovers.  My setup:

Ubuntu 15.10 | qemu-system-x86_64 --version  QEMU emulator version 2.3.0 (Debian 1:2.3+dfsg-5ubuntu9)
HW = Dell Precision M6600 with Intel(R) Core(TM) i7-2760QM CPU

I agree with other comments that it seems related to high disk I/O as
the problem seems to occur during VM install or other VM operations
which read/write large amounts of data.

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https://bugs.launchpad.net/bugs/1481272

Title:
  main-loop: WARNING: I/O thread spun for 1000 iterations

Status in QEMU:
  New

Bug description:
  I compile the latest qemu to launch a VM but the monitor output the
  "main-loop: WARNING: I/O thread spun for 1000 iterations".

  # /usr/local/bin/qemu-system-x86_64 -name rhel6 -S -no-kvm -m 1024M -realtime mlock=off -smp 1,sockets=1,cores=1,threads=1 -uuid c9dd2a5c-40f2-fd3d-3c54-9cd84f8b9174 -rtc base=utc  -drive file=/home/samba-share/ubuntu.img,if=none,id=drive-virtio-disk0,format=qcow2,cache=none -device virtio-blk-pci,bus=pci.0,addr=0x4,drive=drive-virtio-disk0,id=disk,serial=425618d4-871f-4021-bc5d-bcd7f1b5ca9c,bootindex=0 -vnc :1 -boot menu=on -monitor stdio
  QEMU 2.3.93 monitor - type 'help' for more information
  (qemu) c
  (qemu) main-loop: WARNING: I/O thread spun for 1000 iterations               <-----------------------

  qemu]# git branch -v
  * master               e95edef Merge remote-tracking branch 'remotes/sstabellini/tags/xen-migration-2.4-tag' into staging

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