Messages in this thread | | | Date | Tue, 29 Nov 2016 22:15:12 +0100 | From | Borislav Petkov <> | Subject | Re: AMD Bulldozer topology regression since 4.6 |
| |
On Tue, Nov 29, 2016 at 10:02:00PM +0100, Brice Goglin wrote: > However thread_siblings isn't back to where it was in 4.5. Now we have a > single bit in each thread_siblings mask. That's correct with respect to > the sysfs topology documentation. In 4.5, there were two bits (one for > each core of the compute unit), which was wrong (cores with different > core_ids shouldn't appear in each other thread_siblings). I assumed that > these processors had to break the sysfs topology documentation to expose > the concept of "dual-core compute-unit" which somehow sits between > hyperthreading and dual-core.
This is exactly the problem - there's never proper fitting of the compute unit "ideology" in the whole topology view. So what we're doing now is revert to the old strategy of keeping Bulldozer have core_id == thread_id. Basically, all CU threads are cores, as they're more powerful than, say, SMT threads, but they still share an FPU.
So it is a different kind of sharing and it's kinda, well, different. There's no other way to put it.
> I personally do not care much about this regression, not sure about > other user-space tools? > > Another minor related change: /proc/cpuinfo shows "cpu cores : 16" > instead of "8".
Can you send me the whole thing? Offlist is fine too.
Thanks.
-- Regards/Gruss, Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg) --
| |