Date: Wed, 20 Jan 2010 10:35:55 +0100
From: Andi Kleen <andi@firstfloor.org>
To: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>, LKML <linux-kernel@vger.kernel.org>,
       Ingo Molnar <mingo@elte.hu>, Paul Mackerras <paulus@samba.org>,
       Stephane Eranian <eranian@googlemail.com>,
       Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Frederic Weisbecker <fweisbec@gmail.com>,
       Xiao Guangrong <xiaoguangrong@cn.fujitsu.com>,
       Dan Terpstra <terpstra@eecs.utk.edu>, Philip Mucci <mucci@eecs.utk.edu>,
       Maynard Johnson <mpjohn@us.ibm.com>, Carl Love <cel@us.ibm.com>
Subject: Re: [RFC] perf_events: support for uncore a.k.a. nest units
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> Yes, I agree.  Also it's easy to construct a system design that doesn't 
> have a hierarchical topology.  A simple example would be a cluster of 32 
> nodes, each of which is connected to its 31 neighbors.  Perhaps for the 

I doubt it's needed or useful to describe all details of an interconnect.

If detailed distance information is needed a simple table like
the SLIT table exported by ACPI would seem easier to handle.

But at least some degree of locality (e.g. "local memory controller")
would make sense.


> purposes of just enumerating PMUs, a tree might be sufficient, but it's not 
> clear to me that it is mathematically sufficient for all topologies, not to 
> mention if it's intuitive enough to use.  For example, 
> highly-interconnected components might require that PMU leaf nodes be 
> duplicated in multiple branches, i.e. PMU paths might not be unique in some 
> topologies.

We already have cyclical graphs in sysfs using symlinks. I'm not 
sure they are all that easy to parse/handle, but at least they
can be described.

-Andi

-- 
ak@linux.intel.com -- Speaking for myself only.
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