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

[Eddie Yen]

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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