Messages in this thread | | | Date | Tue, 06 May 2014 16:20:59 -0400 | From | Rik van Riel <> | Subject | Re: [PATCH RFC/TEST] sched: make sync affine wakeups work |
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On 05/06/2014 09:25 AM, Peter Zijlstra wrote: > On Sun, May 04, 2014 at 08:41:09AM -0400, Rik van Riel wrote: >> Even on 8-node DL980 systems, the NUMA distance in the >> SLIT table is less than RECLAIM_DISTANCE, and we will >> do wake_affine across the entire system. > > Yeah, so the problem is that (AFAIK) ACPI doesn't actually specify a > metric for the SLIT distance. This (in as far as BIOS people would care > to stick to specs anyhow) has lead to the 'fun' situation where BIOS > engineers tweak SLIT table values to make OSes behave as they thing it > should. > > So if the BIOS engineer finds that this system should have < > RECLAIM_DISTANCE it will simply make the table such that the max SLIT > value is below that. > > And yes, I've seen this :-(
It appears to be the case on the vast majority of the NUMA systems that are actually in use.
To me, this suggests that we should probably deal with it.
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