RE: [Xen-devel] [PATCH] Export Multicore information

["Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>]

Hi Keir,
   The most interesting field of the cacheinfo is "shared cpus map".
Take an example of clowertown. It has 4 cores per socket. Basically
there are 2 duel-core dies in the packages. So there are 2 pairs of
cores in the packages which share the L2 caches among the pair itself,
not across the package.
   So with this information the end user/admin would have better
selection when she decides to split the cores from a single package
across multiple domains.

Thanks & Regards,
Nitin 
Open Source Technology Center, Intel Corporation.
------------------------------------------------------------------------
-
The mind is like a parachute; it works much better when it's open.

-----Original Message-----
From: Keir Fraser [mailto:Keir.Fraser@xxxxxxxxxxxx] 
Sent: Monday, December 11, 2006 11:39 PM
To: Kamble, Nitin A; John Levon
Cc: Yu, Wilfred; Ian Pratt; Xen devel list; Yang, Fred; Mallick, Asit K;
Nakajima, Jun; Keir Fraser
Subject: Re: [Xen-devel] [PATCH] Export Multicore information

On 12/12/06 12:26 am, "Kamble, Nitin A" <nitin.a.kamble@xxxxxxxxx>
wrote:

>    Thanks for your comments. The situation is, dom0 may not see all
the
> processors in the system. Only hyper visor is capable of seeing all. I
> would let tools/apps on dom0 to see information about CPUs assigned to
> dom0, not the whole set available in the system. So it is necessary to
> have a hyper visor specific interface, and in my opinion xm is the
best
> choice for that.

A strong argument against 'xm cacheinfo' and the required extra
hypercall is
that x86 cache hierarchies are always symmetric, to the best of my
knowledge. So it does not matter which CPU dom0 happens to interrogate
for
cache info -- the information can be extrapolated to all other CPUs in
the
system. So the admin can run one of the many little tools that can be
downloaded and that dump out interesting CPUID information. The physical
CPU
topology hypercall (i.e., the smaller half of your patch) is more
interesting to me.

 -- Keir

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