Messages in this thread | | | Date | Wed, 20 Jan 2010 11:28:59 -0800 | From | Corey Ashford <> | Subject | Re: [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
| |