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

Tue Dec 29 10:38:01 UTC 2015

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