[vfio-users] Optimize vm and host performance, is dual xeon the way ?

Tue Dec 29 10:50:10 UTC 2015

Sure but how do i do that?
I can check the memory usage on the guest using rivaturner ( i don't use
more than 9gB of ram, i have 16), may the problem come from the balloon
option at the end of the xml ? Dunno how to check the rest though.

For disk io i use a separate ssd for the vm and all other disks are not
mount when i launch it (it will fail otherwise if i remember correctly).
But talking about swap i need to check where the swap for fedora is, maybe
there is something worth checking here.

I already reduced the memory i assign to the windows vm because otherwise
it would fail, apparently fedora likes to take a lot of ram of nothing.

2015-12-29 11:38 GMT+01:00 Karsten Elfenbein <karsten.elfenbein at gmail.com>:

> If it takes time to recover after exiting the VM I think you have a
> different problem than CPU pinning.
> While my Windows VM is idle all CPU cores are idle on the host as well.
>
> Time to recover sounds more like a system that swapped out memory to
> make room for the VM. After exiting it needs the swapped out process
> memory which takes time.
> Can you check the memory/swap/disk io usage?
>
> 2015-12-29 11:13 GMT+01:00 thibaut noah <thibaut.noah at gmail.com>:
> > I'll try to set the topology tonight.
> > Fedora still takes time to be fully operationnal after exiting windows,
> and
> > i use windows only not putting more load on fedora, weird.
> > My goal by tweaking the vcpu is to get the best possible performance i
> can
> > reach without crippling the host os.
> > dual xeon are indeed expensive, specially those with 3+ghz, dunno if i
> need
> > that much cpu for windows though i'm not sure, i can try by just using
> > 2physical cores and see how it goes for both os, would be nice if i could
> > apply the new patch to move my keyboard from guest to host T_T
> >
> > 2015-12-28 10:54 GMT+01:00 Karsten Elfenbein <
> karsten.elfenbein at gmail.com>:
> >>
> >> It just hands the layout of your CPU to the guest. So apps can decide
> >> on threading.
> >>
> >> Pinning the CPU to avoid CPU 0 and 4 will reduce the performance a bit
> >> as a complete physical core is reserved for the host OS.
> >> There are faster Desktop CPUs to compensate if needed but dual Xeon
> >> that can keep up in single thread performance are expensive and you
> >> would need 2 CPU + memory + board.
> >>
> >>
> >>
> >> 2015-12-28 10:24 GMT+01:00 Eddie Yen <missile0407 at gmail.com>:
> >> >
> >> > This should provide the guest some details of the provided vCPUs:
> >> >
> >> > <topology sockets='1' cores='3' threads='2'/>
> >> >
> >> >
> >> > I tested this method before, using the 4820K.
> >> > The result I got is the performance not get better that set whole
> >> > threads as
> >> > cores when tested 3DMark.
> >> > But I didn't pinning 0 and 4 thread to host.
> >> >
> >> > I'll test it again soon.
> >> >
> >> > 2015-12-28 17:13 GMT+08:00 Karsten Elfenbein
> >> > <karsten.elfenbein at gmail.com>:
> >> >>
> >> >> Hi,
> >> >>
> >> >> that looks good. Processors 0 and 4 are not used in pinning and
> remain
> >> >> on the host OS. https://en.wikipedia.org/wiki/Hyper-threading
> >> >> Basically as soon as you load one OS CPU on a physical core the other
> >> >> HT core will be able to perform a lot less stuff.
> >> >>
> >> >> This should provide the guest some details of the provided vCPUs:
> >> >> <topology sockets='1' cores='3' threads='2'/>
> >> >>
> >> >>
> >> >> 2015-12-28 6:55 GMT+01:00 thibaut noah <thibaut.noah at gmail.com>:
> >> >> > So is this the right emulation? If i understand correctly what i'm
> >> >> > trying to
> >> >> > get is a 3cores with 2threads per core ? (so 6cores pinned?)
> >> >> > I don't have that much knowledge in cpu so i'm kinda lost here.
> >> >> >
> >> >> > <cputune>
> >> >> >     <vcpupin vcpu='0' cpuset='1'/>
> >> >> >     <vcpupin vcpu='1' cpuset='2'/>
> >> >> >     <vcpupin vcpu='2' cpuset='3'/>
> >> >> >     <vcpupin vcpu='3' cpuset='5'/>
> >> >> >     <vcpupin vcpu='4' cpuset='6'/>
> >> >> >     <vcpupin vcpu='5' cpuset='7'/>
> >> >> >   </cputune>
> >> >> >
> >> >> > 2015-12-26 18:53 GMT+01:00 Karsten Elfenbein
> >> >> > <karsten.elfenbein at gmail.com>:
> >> >> >>
> >> >> >> check that the 2 cores for the host OS are on the same physical
> core
> >> >> >> and that the VM does not use those 2 processors with the same core
> >> >> >> id
> >> >> >>
> >> >> >> cat /proc/cpuinfo | grep -e processor -e 'core id'
> >> >> >>
> >> >> >> CPU 0-3 should be the core 0-3
> >> >> >> CPU 4-7 should be the core 0-3 again with HT
> >> >> >>
> >> >> >> so leaving out CPU 0 and 4 should keep core 0 idle and the host OS
> >> >> >> responsive
> >> >> >>
> >> >> >> taskset 1-3,5-7 startVM.sh
> >> >> >>
> >> >> >> Karsten
> >> >> >>
> >> >> >> 2015-12-26 12:56 GMT+01:00 Eddie Yen <missile0407 at gmail.com>:
> >> >> >> > Pining CPU can reduce the happening that host and guest using
> the
> >> >> >> > same
> >> >> >> > thread at the same time.
> >> >> >> >
> >> >> >> > And I don't know which program you're using on Fedora, so I
> don't
> >> >> >> > have
> >> >> >> > quite
> >> >> >> > answer that 2 threads is enough for host or not.
> >> >> >> > It's all depends on your usage case.
> >> >> >> >
> >> >> >> > 2015-12-26 19:44 GMT+08:00 thibaut noah <thibaut.noah at gmail.com
> >:
> >> >> >> >>
> >> >> >> >> My cpu is a i7 4790k, is pinning the cpu usefull ? I'll try to
> >> >> >> >> derp
> >> >> >> >> a
> >> >> >> >> bit
> >> >> >> >> with the vcpu thing, just afraid 2 threads aren't enough for
> >> >> >> >> fedora
> >> >> >> >> :/
> >> >> >> >>
> >> >> >> >> 2015-12-26 11:59 GMT+01:00 Eddie Yen <missile0407 at gmail.com>:
> >> >> >> >>>
> >> >> >> >>> I forgot your CPU type, so I don't know about your case.
> >> >> >> >>>
> >> >> >> >>> But, as I'm using 4820K, I usually using 4 to 6 threads gave
> to
> >> >> >> >>> VM,
> >> >> >> >>> only
> >> >> >> >>> use 2 threads for Fedora host.
> >> >> >> >>> And most important is vCPU tweaks, especially CPU topology and
> >> >> >> >>> Hyper-V.
> >> >> >> >>>
> >> >> >> >>> For me, I usually set topology as "sockets=1 cores=6
> threads=1"
> >> >> >> >>> if
> >> >> >> >>> using
> >> >> >> >>> 6 threads from host.
> >> >> >> >>> Then set cpuset= to let vCPU worked on pointed CPU threads.
> >> >> >> >>>
> >> >> >> >>> IME, set all threads as vCPU cores can got better performance
> on
> >> >> >> >>> Windows
> >> >> >> >>> 10.
> >> >> >> >>>
> >> >> >> >>> 2015-12-26 18:00 GMT+08:00 thibaut noah
> >> >> >> >>> <thibaut.noah at gmail.com>:
> >> >> >> >>>>
> >> >> >> >>>> Hello guys merry christmas ! o/
> >> >> >> >>>> My current issue is vm and host optimization, i use my
> windows
> >> >> >> >>>> 10
> >> >> >> >>>> vm
> >> >> >> >>>> for
> >> >> >> >>>> gaming purposes only (like most of us i think), problem is,
> to
> >> >> >> >>>> keep
> >> >> >> >>>> my
> >> >> >> >>>> performances on windows high i drain too much ressources on
> my
> >> >> >> >>>> fedora
> >> >> >> >>>> host
> >> >> >> >>>> thus making it almost useless (also when leaving the vm i
> most
> >> >> >> >>>> of
> >> >> >> >>>> the
> >> >> >> >>>> time
> >> >> >> >>>> found myself unable to use fedora at all so i have to
> >> >> >> >>>> reboot...).
> >> >> >> >>>> So is it possible to improve performances to the max on the
> >> >> >> >>>> guest
> >> >> >> >>>> without almost killing the host ?
> >> >> >> >>>> Should i consider switching my gear for a bi-xeon? (to assign
> >> >> >> >>>> one
> >> >> >> >>>> fully
> >> >> >> >>>> to the host and one to the guest)
> >> >> >> >>>> I'm actually not sure about what happen here, does anyone ran
> >> >> >> >>>> into
> >> >> >> >>>> the
> >> >> >> >>>> same sort of issue?
> >> >> >> >>>> Have a good day
> >> >> >> >>>>
> >> >> >> >>>> _______________________________________________
> >> >> >> >>>> vfio-users mailing list
> >> >> >> >>>> vfio-users at redhat.com
> >> >> >> >>>> https://www.redhat.com/mailman/listinfo/vfio-users
> >> >> >> >>>>
> >> >> >> >>>
> >> >> >> >>
> >> >> >> >
> >> >> >> >
> >> >> >> > _______________________________________________
> >> >> >> > vfio-users mailing list
> >> >> >> > vfio-users at redhat.com
> >> >> >> > https://www.redhat.com/mailman/listinfo/vfio-users
> >> >> >> >
> >> >> >
> >> >> >
> >> >
> >> >
> >
> >
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listman.redhat.com/archives/vfio-users/attachments/20151229/796accbb/attachment.htm>