[Qemu-devel] [Bug 1766904] Re: Creating high hdd load (with constant fsyncs) on a SATA disk leads to freezes and errors in guest dmesg

[John Snow]

Relevant bits appear to be:

-M pc-i1440fx-2.8
-cpu IvyBridge
-m 2048 
-realtime mlock=off 
-smp 2,sockets=2,cores=1,threads=1
-device ahci,id=sata0,bus=pci.0,addr=0x7 
-drive 
file=/home/user/data/work/virt-images/myvm.local.qcow2,format=qcow2,if=none,id=drive-sata0-0-0
 
-device ide-hd,bus=sata0.0,drive=drive-sata0-0-0,id=sata0-0-0,bootindex=1 

So this is a 2.8 PC machine that we've configured to use AHCI instead. I
see some blips about CHS being zero, but that's expected in response to
a (successful) flush (0xE7) command, so it looks like it's stalling out.
I'll have to try to reproduce and see if I can trigger the hang.

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https://bugs.launchpad.net/bugs/1766904

Title:
  Creating high hdd load (with constant fsyncs) on a SATA disk leads to
  freezes and errors in guest dmesg

Status in QEMU:
  New

Bug description:
  After upgrading from qemu 2.10.0+dfsg-2 to 2.12~rc3+dfsg-2 (on debian
  sid host), centos 7 guest started to show freezes and ata errors in
  dmesg during hdd workloads with writing many small files and repeated
  fsyncs.

  Host kernel 4.15.0-3-amd64.
  Guest kernel 3.10.0-693.21.1.el7.x86_64 (slightly older guest kernel was 
tested too with same result).

  Script that reproduces the bug (first run usualy goes smooth, second
  and later runs result in dmesg errors and freezes):

  http://paste.debian.net/hidden/472fb220/

  Sample of error messages in guest dmesg:

  http://paste.debian.net/hidden/8219e234/

  This vm is launchd using virsh start. VM launch command (from logfile
  in /var/log/libvirt/qemu/):

  http://paste.debian.net/plainh/5604126f

  A workaround that I am using right now: I have detached this SATA
  storage and reattached the same .qcow2 file as SCSI - this has fixed
  the issue for me.

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