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

Tue Dec 29 10:13:43 UTC 2015

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
> >> >> >
> >> >
> >> >
> >
> >
>
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