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

[Andreas Gustafsson]

I no longer see the "WARNING: I/O thread spun for 1000 iterations"
message.  A bisection showed that it disappeared with the following
commit:

commit e330c118f2a5a5365409b123cd0dd2c7d575bf05
Author: Paolo Bonzini <address@hidden>
Date:   Fri Mar 3 11:51:07 2017 +0100

    main-loop: remove now unnecessary optimization

    This optimization is not necessary anymore, because the vCPU now drops
    the I/O thread lock even with TCG.  Drop it to simplify the code and
    avoid the "I/O thread spun for 1000 iterations" warning.

    Reviewed-by: Alex Bennée <address@hidden>
    Reviewed-by: Edgar E. Iglesias <address@hidden>
    Signed-off-by: Paolo Bonzini <address@hidden>

The amount of system time consumed by the qemu process, which had
incrased 300-fold with commit 05e514b1d4d5bd4209e2c8bbc76ff05c85a235f3,
is also back to normal.

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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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