From email at andrewnesbit.org Wed Sep 6 12:26:44 2017 Content-Type: multipart/mixed; boundary="===============3590075039898081528==" MIME-Version: 1.0 From: Andrew Nesbit To: users at ovirt.org Subject: Re: [ovirt-users] cpu, core and thread mappings Date: Wed, 06 Sep 2017 13:19:59 +0100 Message-ID: In-Reply-To: CAG2kNCxoVeFauUqaGuB-ToDA=pAbwQ9WZON4EUm+sXFkNuudrA@mail.gmail.com --===============3590075039898081528== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable --Apple-Mail-FC5CF2F4-77D9-4AB3-AECA-43D5365F3844 Content-Type: text/plain; charset=3Dus-ascii Content-Transfer-Encoding: quoted-printable > Are there any documents going more deeply in these sort of considerations= ?=3D This is exactly what I have been searching for lately, too. Please let me = k=3D now if you find anything (or blog posts, forums, books, etc). Thank you! Sent from my mobile phone > On 6 Sep 2017, at 12:47, Gianluca Cecchi wr= ote=3D : >=3D20 > Hello, > I was talking with a guy expert in VMware and discussing performance of V= M=3D s in respect of virtual cpus assigned to them in relation with mapping with= t=3D he real hw of the hypervisor underneath. >=3D20 > One of the topics was numa usage and its overheads in case of a "too" big= V=3D M, in terms of both number of vcpus and memory amount. > Eg:=3D20 > suppose host has 2 intel based sockets, with 6 cores and HT enabled and h= a=3D s 96Gb of ram (distributed 48+48 between the 2 processors) > suppose I configure a VM with 16 vcpus (2:4:2): would be the mapping resp= e=3D cted at physical level or only a sort of "hint" for the hypervisor? > Can I say that it would perform better if I configure it 12 vcpus and map= p=3D ing 1:6:2, because it can stay all inside one cpu? >=3D20 > And what if I define a VM with 52Gb of ram? Can I say that it would perfo= r=3D m in general better if I try to get it all in one cpu related memory slots = (=3D eg not more than 48Gb in my example)? >=3D20 > Are there any documents going more deeply in these sort of considerations= ?=3D >=3D20 > Also, if one goes and sizes so that the biggest VM is able to all-stay in= s=3D ide one cpu-memory, does it make sense to say that it will perform better i= n=3D this scenario a cluster composed by 4 nodes, each one with 1 socket and 48= G=3D b of memory instead of a cluster of 2 nodes, each one with 2 sockets and 96= G=3D b of ram? >=3D20 > Hope I have clarified my questions/doubts. >=3D20 >=3D20 > Thanks in advance for any insight, > Gianluca =3D20 > _______________________________________________ > Users mailing list > Users(a)ovirt.org > http://lists.ovirt.org/mailman/listinfo/users --Apple-Mail-FC5CF2F4-77D9-4AB3-AECA-43D5365F3844 Content-Type: text/html; charset=3Dutf-8 Content-Transfer-Encoding: quoted-printable
Are there any documents going more deep= l=3D y in these sort of considerations?

This is exactly what I have been searching f= o=3D r lately, too.  Please let me know if you find anything (or blog posts= ,=3D forums, books, etc).  Thank you!

Sent from my mobile phone

On 6 Sep 2017, at 12:47, Gianluca Cecchi <gianluca.cecchi(a)gmail.com> wrote:
Hello,
I was talk= ing w=3D ith a guy expert in VMware and discussing performance of VMs in respect of = v=3D irtual cpus assigned to them in relation with mapping with the real hw of t= h=3D e hypervisor underneath.

One of the topics was num= a=3D usage and its overheads in case of a "too" big VM, in terms of both number= o=3D f vcpus and memory amount.
Eg: 
suppose host has 2= i=3D ntel based sockets, with 6 cores and HT enabled and has 96Gb of ram (distri= b=3D uted 48+48 between the 2 processors)
suppose I configure a VM wit= h=3D 16 vcpus (2:4:2): would be the mapping respected at physical level or only= a=3D sort of "hint" for the hypervisor?
Can I say that it would perfo= r=3D m better if I configure it 12 vcpus and mapping 1:6:2, because it can stay = a=3D ll inside one cpu?

And what if I define a VM with = 5=3D 2Gb of ram? Can I say that it would perform in general better if I try to g= e=3D t it all in one cpu related memory slots (eg not more than 48Gb in my examp= l=3D e)?

Are there any documents going more deeply in t= h=3D ese sort of considerations?

Also, if one goes and = s=3D izes so that the biggest VM is able to all-stay inside one cpu-memory, does= i=3D t make sense to say that it will perform better in this scenario a cluster = c=3D omposed by 4 nodes, each one with 1 socket and 48Gb of memory instead of a = c=3D luster of 2 nodes, each one with 2 sockets and 96Gb of ram?

<= /=3D div>
Hope I have clarified my questions/doubts.


Thanks in advance for any insight,
Gianluca  = ;=3D
_________________= ___=3D ___________________________
Users mailing list
Users(a)ovirt.org
<= span>http://lists.ovir= t.o=3D rg/mailman/listinfo/users
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