From: Valentin Schneider <valentin.schneider@arm.com>
To: "Song Bao Hua \(Barry Song\)" <song.bao.hua@hisilicon.com>,
"linux-kernel\@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: "mingo\@kernel.org" <mingo@kernel.org>,
"peterz\@infradead.org" <peterz@infradead.org>,
"vincent.guittot\@linaro.org" <vincent.guittot@linaro.org>,
"dietmar.eggemann\@arm.com" <dietmar.eggemann@arm.com>,
"morten.rasmussen\@arm.com" <morten.rasmussen@arm.com>,
"mgorman\@suse.de" <mgorman@suse.de>
Subject: RE: [PATCH 1/1] sched/topology: Make sched_init_numa() use a set for the deduplicating sort
Date: Mon, 01 Feb 2021 12:03:48 +0000 [thread overview]
Message-ID: <jhjy2g8yoyj.mognet@arm.com> (raw)
In-Reply-To: <e12ec4f50c6c41db84f601038d3ee39c@hisilicon.com>
On 29/01/21 02:02, Song Bao Hua (Barry Song) wrote:
>> -----Original Message-----
>> From: Valentin Schneider [mailto:valentin.schneider@arm.com]
>> That is another thing that's worth considering. Morten was arguing that if
>> the distance between two nodes is so tiny, it might not be worth
>> representing it at all in the scheduler topology.
>
> Yes. I agree it is a different thing. Anyway, I saw your patch has been
> in sched tree. One side effect your patch is the one more sched_domain
> level is imported for this topology:
>
> 24
> X X XXX X X X X X X XXX
> XX XX X XXXXX
> XXX X
> XX XXX
> XX 22 XXX
> X XXXXXXX XX
> X XXXXX XXXXXXXXX XXXX
> XX XXX XX X XX X XX
> +--------+ +---------+ +---------+ XX+---------+
> | 0 | 12 | 1 | 20 | 2 | 12 |3 |
> | +-----------+ +----------+ +--------+ |
> +---X----+ +---------+ +--X------+ +---------+
> X X
> XX X
> X XX
> XX XX
> XX X
> X XXX XXX
> X XXXXXX XX XX X X X XXXX
> 22
> Without the patch, Linux will use 10,12,22,24 to build sched_domain;
> With your patch, Linux will use 10,12,20,22,24 to build sched_domain.
>
> So one more layer is added. What I have seen is that:
>
> For node0 sched_domain <=12 and sched_domain <=20 span the same range
> (node0, node1). So one of them is redundant. then in cpu_attach_domain,
> the redundant one is dropped due to "remove the sched domains which
> do not contribute to scheduling".
>
> For node1&2, the origin code had no "20", thus built one less sched_domain
> level.
>
Right, that domain degeneration should get you to the same result. We do
want to make sure we're handling every distance value in the table; the
gist is to "stupidly" build every domain / level we can, and if some are
redundant we can remove them after the fact.
> What is really interesting is that removing 20 actually gives better
> benchmark in speccpu :-)
>
>
>>
>> > Thanks
>> > Barry
>
> Thanks
> Barry
next prev parent reply other threads:[~2021-02-01 12:04 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-22 12:39 [PATCH 0/1] sched/topology: NUMA distance deduplication Valentin Schneider
2021-01-22 12:39 ` [PATCH 1/1] sched/topology: Make sched_init_numa() use a set for the deduplicating sort Valentin Schneider
2021-01-25 2:23 ` Song Bao Hua (Barry Song)
2021-01-25 9:26 ` Valentin Schneider
2021-01-25 16:45 ` Valentin Schneider
2021-01-25 21:35 ` Song Bao Hua (Barry Song)
2021-01-28 14:47 ` Valentin Schneider
2021-01-29 2:02 ` Song Bao Hua (Barry Song)
2021-02-01 12:03 ` Valentin Schneider [this message]
2021-02-01 9:53 ` Dietmar Eggemann
2021-02-01 10:19 ` Vincent Guittot
2021-02-01 10:35 ` Song Bao Hua (Barry Song)
2021-02-01 11:55 ` Valentin Schneider
2021-02-02 10:03 ` [tip: sched/core] sched/topology: Fix sched_domain_topology_level alloc in sched_init_numa() tip-bot2 for Dietmar Eggemann
2021-02-17 13:17 ` tip-bot2 for Dietmar Eggemann
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