lkml.org 
[lkml]   [2010]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] perf_events: support for uncore a.k.a. nest units


On 1/20/2010 1:35 AM, Andi Kleen wrote:
>> 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.
>

At this point, I don't see a need for that level of detail either.

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

Thanks for the pointer. I didn't know about the ACPI SLIT and SRAT tables until
your post. Having had a quick look at them, I don't think they'd be that
helpful to us, at least at this point.

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

I think locality could be determined by looking at the device tree. For
example, a memory controller for a particular processor chip would be a
subdirectory of that chip.

>
>> 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.

Good point.

--
Regards,

- Corey

Corey Ashford
Software Engineer
IBM Linux Technology Center, Linux Toolchain
Beaverton, OR
503-578-3507
cjashfor@us.ibm.com



\
 
 \ /
  Last update: 2010-01-20 20:31    [W:1.563 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site