lkml.org 
[lkml]   [2014]   [May]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH RFC/TEST] sched: make sync affine wakeups work
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.

--
All rights reversed


\
 
 \ /
  Last update: 2014-05-06 23:21    [W:0.108 / U:1.120 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site