linux-kernel - Re: [PATCH RFC/TEST] sched: make sync affine wakeups work

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <5369442B.9010505@redhat.com>
Date:	Tue, 06 May 2014 16:20:59 -0400
From:	Rik van Riel <riel@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Preeti Murthy <preeti.lkml@...il.com>, umgwanakikbuti@...il.com,
	LKML <linux-kernel@...r.kernel.org>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Ingo Molnar <mingo@...nel.org>, george.mccollister@...il.com,
	ktkhai@...allels.com, Preeti U Murthy <preeti@...ux.vnet.ibm.com>
Subject: Re: [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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/