Re: Performance issue

[Vadim Rozenfeld <vrozenfe@redhat.com>]

On Wednesday, November 28, 2012 09:09:29 PM George-Cristian Bîrzan wrote:
> On Wed, Nov 28, 2012 at 1:39 PM, Vadim Rozenfeld <vrozenfe@redhat.com> 
wrote:
> > On Tuesday, November 27, 2012 11:13:12 PM George-Cristian Bîrzan wrote:
> >> On Tue, Nov 27, 2012 at 10:38 PM, Vadim Rozenfeld <vrozenfe@redhat.com>
> > 
> > wrote:
> >> > I have some code which do both reference time and invariant TSC but it
> >> > will not work after migration. I will send it later today.
> >> 
> >> Do you mean migrating guests? This is not an issue for us.
> > 
> > OK, but don't say I didn't warn you :)
> > 
> > There are two patches, one for kvm and another one for qemu.
> > you will probably need to rebase them.
> > Add "hv_tsc" cpu parameter to activate this feature.
> > you will probably need to deactivate hpet by adding "-no-hpet"
> > parameter as well.
> 
> I've also added +hv_relaxed since then, but this is the command I'm

I would suggest activating relaxed timing for all W2K8R2/Win7 guests.

> using now and there's no change:
> 
> /usr/bin/qemu-kvm -name b691546e-79f8-49c6-a293-81067503a6ad -S -M
> pc-1.2 -enable-kvm -m 16384 -smp 9,sockets=1,cores=9,threads=1 -uuid
> b691546e-79f8-49c6-a293-81067503a6ad -no-user-config -nodefaults
> -chardev
> socket,id=charmonitor,path=/var/lib/libvirt/qemu/b691546e-79f8-49c6-a293-8
> 1067503a6ad.monitor,server,nowait -mon
> chardev=charmonitor,id=monitor,mode=control -rtc base=utc
> -no-hpet -no-shutdown -device
> piix3-usb-uhci,id=usb,bus=pci.0,addr=0x1.0x2 -drive
> file=/var/lib/libvirt/images/dis-magnetics-2-223101/d8b233c6-8424-4de9-ae3c
> -7c9a60288514,if=none,id=drive-virtio-disk0,format=qcow2,cache=writeback,ai
> o=native -device
> virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=vir
> tio-disk0,bootindex=1 -netdev tap,fd=35,id=hostnet0,vhost=on,vhostfd=36
> -device
> virtio-net-pci,netdev=hostnet0,id=net0,mac=22:2e:fb:a2:36:be,bus=pci.0,addr
> =0x3 -netdev tap,fd=40,id=hostnet1,vhost=on,vhostfd=41 -device
> virtio-net-pci,netdev=hostnet1,id=net1,mac=22:94:44:5a:cb:24,bus=pci.0,addr
> =0x4 -vnc 127.0.0.1:0,password -vga cirrus -device
> virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x6 -cpu host,hv_tsc
> 
> I compiled qemu-1.2.0-24 after applying your patch, used the head for
> KVM, and I see no difference. I've tried setting windows'
> useplatformclock on and off, no change either.
> 
> 
> Other than that, was looking into a profiling trace of the software
> running and a lot of time (60%?) is spent calling two functions from
> hal.dll, HalpGetPmTimerSleepModePerfCounter when I disable HPET, and
> HalpHPETProgramRolloverTimer which do point at something related to
> the timers.
> 
It means that hyper-v time stamp source was not activated.
> Any other thing I can try?
> 
> 
> --
> George-Cristian Bîrzan