Re: Externalize SLIT table

From: Mark Goodwin
Date: Wed Nov 10 2004 - 00:06:58 EST

On Tue, 9 Nov 2004, Matthew Dobson wrote:
On Tue, 2004-11-09 at 12:34, Mark Goodwin wrote:
Once again however, it depends on the definition of distance. For nodes,
we've established it's the ACPI SLIT (relative distance to memory). For
cpus, should it be distance to memory? Distance to cache? Registers? Or

That's the real issue. We need to agree upon a meaningful definition of
CPU-to-CPU "distance". As Jesse mentioned in a follow-up, we can all
agree on what Node-to-Node "distance" means, but there doesn't appear to
be much consensus on what CPU "distance" means.

How about we define cpu-distance to be "relative distance to the
lowest level cache on another CPU". On a system that has nodes with
multiple sockets (each supporting multiple cores or HT "CPUs" sharing
some level of cache), when the scheduler needs to migrate a task it would
first choose a CPU sharing the same cache, then a CPU on the same node,
then an off-node CPU (i.e. falling back to node distance).

Of course, I have no idea if that's anything like an optimal or desirable
task migration policy. Probably depends on cache-trashiness of the task
being migrated.

-- Mark
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at