linux-kernel - Re: [PATCH v3 0/3] sched/topology: optimize topology_span

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Message-ID: <14fd8032-51b2-4182-b74d-699df550ffec@wanadoo.fr>
Date: Wed, 6 Nov 2024 18:58:23 +0100
From: Christophe JAILLET <christophe.jaillet@...adoo.fr>
To: Yury Norov <yury.norov@...il.com>, linux-kernel@...r.kernel.org
Cc: Chen Yu <yu.c.chen@...el.com>, Leonardo Bras <leobras@...hat.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH v3 0/3] sched/topology: optimize topology_span_sane()

Le 06/11/2024 à 17:28, Yury Norov a écrit :
> Last reminder. If you guys don't care, I don't care either.

Hi Yury,

I'm the only one in the To: field, but I'm not a maintainer.

Maybe, try to move people in the Cc: field into the To: field, to 
increase visibility?

CJ

> 
> On Mon, Sep 30, 2024 at 12:15:02PM -0700, Yury Norov wrote:
>> Ping again?
>>
>> On Sat, Sep 14, 2024 at 09:54:43AM -0700, Yury Norov wrote:
>>> Ping?
>>>
>>> On Mon, Sep 02, 2024 at 11:36:04AM -0700, Yury Norov wrote:
>>>> The function may call cpumask_equal with tl->mask(cpu) == tl->mask(i),
>>>> even when cpu != i. In such case, cpumask_equal() would always return
>>>> true, and we can proceed to the next iteration immediately.
>>>>
>>>> Valentin Schneider shares on it:
>>>>
>>>>    PKG can potentially hit that condition, and so can any
>>>>    sched_domain_mask_f that relies on the node masks...
>>>>
>>>>    I'm thinking ideally we should have checks in place to
>>>>    ensure all node_to_cpumask_map[] masks are disjoint,
>>>>    then we could entirely skip the levels that use these
>>>>    masks in topology_span_sane(), but there's unfortunately
>>>>    no nice way to flag them... Also there would be cases
>>>>    where there's no real difference between PKG and NODE
>>>>    other than NODE is still based on a per-cpu cpumask and
>>>>    PKG isn't, so I don't see a nicer way to go about this.
>>>>
>>>> v1: https://lore.kernel.org/lkml/ZrJk00cmVaUIAr4G@yury-ThinkPad/T/
>>>> v2: https://lkml.org/lkml/2024/8/7/1299
>>>> v3:
>>>>   - add topology_cpumask_equal() helper in #3;
>>>>   - re-use 'cpu' as an iterator int the for_each_cpu() loop;
>>>>   - add proper versioning for all patches.
>>>>
>>>> Yury Norov (3):
>>>>    sched/topology: pre-compute topology_span_sane() loop params
>>>>    sched/topology: optimize topology_span_sane()
>>>>    sched/topology: reorganize topology_span_sane() checking order
>>>>
>>>>   kernel/sched/topology.c | 29 +++++++++++++++++++++++++----
>>>>   1 file changed, 25 insertions(+), 4 deletions(-)
>>>>
>>>> -- 
>>>> 2.43.0
> 
>