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

[Karsten Elfenbein]

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
>> >>>>
>> >>>
>> >>
>> >
>> >
>> > _______________________________________________
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>> >
>
>