[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[Qemu-devel] [Bug 1202289] Re: Windows 2008/7 Guest to Guest Very slow 1

From: Ingo Krabbe
Subject: [Qemu-devel] [Bug 1202289] Re: Windows 2008/7 Guest to Guest Very slow 10-20Mbit/s
Date: Sun, 01 May 2016 12:46:10 -0000

I'm not sure yet, but I think the TSO problem affects much more setups,
not only windows guests. You might try to set GSO to off in windows
guests too, if there is such an option (GSO might be a linux kernel

I currently think that we have similar problems with centos7 hosts and
guests as well as with some windows7 guests.

I also read about similar centos6 problems. There is even a original
setup guide for centos6 from redhat, to set "tso off gso off" in the
host bridge adapter, when you use virtio.

This whole topic is disturbingly distributed through several setups. The
diagnosis of this problem is far from being trivial.

You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.

  Windows 2008/7 Guest to Guest Very slow 10-20Mbit/s

Status in QEMU:

Bug description:
  I'm not sure if I'm submitting this to the proper place or not, if
  not, please direct me accordingly.

  At this point I'm starting to get desperate, I'll take any options or
  suggestions that spring to mind:

  Anyway, the problem exists on multiple hosts of various quality.
  From 4 core 8g mem machines to 12 core 64Gig mem machines with LVM and

  Using iperf as the testing utility: (windows guest can be either Windows 7 or 
  -Windows Guest -> Windows Guest averages 20Mbit/s (The problem)
  -Windows Guest -> Host averages 800Mbit/s
  -Host -> Windows Guest averages 1.1Gbit/s
  -Linux Guest -> Host averages 12GBit/s
  -Linux Guest -> Linux Guest averages 10.2Gbit/s

  For windows guests, switching between e1000 and virtio drivers doesn't
  make much of a difference.

  I use openvswitch to handle the bridging (makes bonding nics much

  Disabling TSO GRO on all the host nics, and virtual nics, as well as modding 
the registry using:
  netsh int tcp set global (various params here)  can slightly improve Windows 
-> windows throughput.   up to maybe 100Mbit/s    but even that is spotty at 

  The Particulars of the fastest host which benchmarks about the same as
  the slowest host.

  Ubuntu 12.04 64bit (updated to lastest as of  July 15th)
  Linux cckvm03 3.5.0-36-generic #57~precise1-Ubuntu SMP Thu Jun 20 18:21:09 
UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

  Source: libvirt
  Version: 0.9.8-2ubuntu17.10

  Package: qemu-kvm
  Version: 1.0+noroms-0ubuntu14.8
  Replaces: kvm (<< 1:84+dfsg-0ubuntu16+0.11.0), kvm-data, qemu

  Source: openvswitch
  Version: 1.4.0-1ubuntu1.5


  processor       : 0
  vendor_id       : GenuineIntel
  cpu family      : 6
  model           : 45
  model name      : Intel(R) Xeon(R) CPU E5-2440 0 @ 2.40GHz
  stepping        : 7
  microcode       : 0x70d
  cpu MHz         : 2400.226
  cache size      : 15360 KB
  physical id     : 0
  siblings        : 12
  core id         : 0
  cpu cores       : 6
  apicid          : 0
  initial apicid  : 0
  fpu             : yes
  fpu_exception   : yes
  cpuid level     : 13
  wp              : yes
  flags           : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca 
  pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb 
  scp lm constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc 
  erfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr 
  m pcid dca sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer aes xsave avx 
  ida arat xsaveopt pln pts dtherm tpr_shadow vnmi flexpriority ept vpid
  bogomips        : 4800.45
  clflush size    : 64
  cache_alignment : 64
  address sizes   : 46 bits physical, 48 bits virtual
  power management:

  -Sample KVM line
  usr/bin/kvm -S -M pc-1.0 -enable-kvm -m 4096 -smp 
2,sockets=2,cores=1,threads=1 -name gvexch01 -uuid 
d28ffb4b-d809-3b40-ae3d-2925e6995394 -nodefconfig -nodefaults -chardev 
-mon chardev=charmonitor,id=monitor,mode=control -rtc base=localtime 
-no-shutdown -boot order=dc,menu=on -drive 
-drive if=none,media=cdrom,id=drive-ide0-0-0,readonly=on,format=raw -device 
ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 -netdev 
tap,fd=18,id=hostnet0,vhost=on,vhostfd=21 -device 
-chardev pty,id=charserial0 -device isa-serial,chardev=charserial0,id=serial0 
-usb -device usb-tablet,id=input0 -vnc -vga std -device 

To manage notifications about this bug go to:

reply via email to

[Prev in Thread] Current Thread [Next in Thread]