linux-kernel - Re: [tip:sched/core] sched/numa: Rewrite the CONFIG

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Date:	Thu, 07 Jun 2012 08:34:54 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Alex Shi <lkml.alex@...il.com>, mingo@...nel.org,
	torvalds@...ux-foundation.org, cmetcalf@...era.com,
	tony.luck@...el.com, sivanich@....com, akpm@...ux-foundation.org,
	ralf@...ux-mips.org, greg.pearson@...com, ink@...assic.park.msu.ru,
	tglx@...utronix.de, rth@...ddle.net,
	kamezawa.hiroyu@...fujitsu.com, paulus@...ba.org,
	linux-kernel@...r.kernel.org, hpa@...or.com, anton@...ba.org,
	lethal@...ux-sh.org, davem@...emloft.net, benh@...nel.crashing.org,
	dhowells@...hat.com, mattst88@...il.com, fenghua.yu@...el.com,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:sched/core] sched/numa: Rewrite the CONFIG_NUMA sched domain
 support

On 06/06/2012 05:15 PM, Peter Zijlstra wrote:

> On Wed, 2012-06-06 at 15:43 +0800, Alex Shi wrote:
>>> +       /*
>>> +        * O(nr_nodes^2) deduplicating selection sort -- in order to find the
>>> +        * unique distances in the node_distance() table.
>>> +        *
>>> +        * Assumes node_distance(0,j) includes all distances in
>>> +        * node_distance(i,j) in order to avoid cubic time.
>>
>> Curious for other platforms node_distance number, actually, this
>> assumption is right for what I saw Intel platforms. but it is not
>> match acpispec50.pdf:
>>
>> Table 6-152 Example Relative Distances Between Proximity Domains
>> Proximity Domain 0 1 2 3
>> 0 10 15 20 18
>> 1 15 10 16 24
>> 2 20 16 10 12
>> 3 18 24 12 10
> 
> Yes I know its allowed, I just haven't seen it in practice.


I see. Thanks.

> 
> I've got a patch that validates this assumption if you boot with
> "sched_debug". If we ever run into such a setup we might need to fix
> this -- it shouldn't be too hard, just expensive.


Sure.
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