[Qemu-devel] [Bug 1091241] Re: NetBSD/i386 6.0 guest suffers interrupt storm since qemu BIOS update

[Aurelien Jarno]

** Changed in: qemu
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1091241

Title:
  NetBSD/i386 6.0 guest suffers interrupt storm since qemu BIOS update

Status in QEMU:
  Fix Released

Bug description:
  Since the pc-bios update of qemu commit
  d7a51dbbaa70677846453f8c961590913052dd86, booting a NetBSD/i386 guest
  takes a very long time, apparently due to interrupt load.

  For example, booting the NetBSD/i386 6.0 serial console install CD
  with

    wget 
ftp://ftp.netbsd.org/pub/NetBSD/NetBSD-6.0/i386/installation/cdrom/boot-com.iso
    qemu-system-i386 -nographic -cdrom boot-com.iso

  used to take less than a minute, but now takes more like ten minutes
  to enter the "sysinst" installer; it's so slow that at first I thought
  it had hung.  If I then exit the installer and type "vmstat -i", it
  shows a high interrupt rate on ioapic0 pin 9:

  # vmstat -i
  interrupt                                     total     rate
  cpu0 timer                                   336942      102
  ioapic0 pin 9                             256791232    78052
  ioapic0 pin 1                                     1        0
  ioapic0 pin 15                                  345        0
  ioapic0 pin 4                                   102        0
  ioapic0 pin 6                                     1        0
  Total                                     257128623    78154

  According to dmesg, this is the piixpm0 device:

  # dmesg
  [...]
  piixpm0 at pci0 dev 1 function 3: vendor 0x8086 product 0x7113 (rev. 0x03)
  timecounter: Timecounter "piixpm0" frequency 3579545 Hz quality 1000
  piixpm0: 24-bit timer
  piixpm0: interrupting at ioapic0 pin 9
  [...]

  Versions of qemu lacking commit
  d7a51dbbaa70677846453f8c961590913052dd86 do not have this problem.

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