From: Morten Rasmussen <morten.rasmussen@arm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@redhat.com, dietmar.eggemann@arm.com, yuyang.du@intel.com,
vincent.guittot@linaro.org, mgalbraith@suse.de,
sgurrappadi@nvidia.com, freedom.tan@mediatek.com,
keita.kobayashi.ym@renesas.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 05/13] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag
Date: Mon, 15 Aug 2016 12:43:08 +0100 [thread overview]
Message-ID: <20160815114308.GB3391@e105550-lin.cambridge.arm.com> (raw)
In-Reply-To: <20160815105459.GS6879@twins.programming.kicks-ass.net>
On Mon, Aug 15, 2016 at 12:54:59PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 25, 2016 at 02:34:22PM +0100, Morten Rasmussen wrote:
> > @@ -6336,14 +6338,16 @@ static int sched_domains_curr_level;
> > * SD_NUMA - describes NUMA topologies
> > * SD_SHARE_POWERDOMAIN - describes shared power domain
> > *
> > - * Odd one out:
> > + * Odd ones out:
> > * SD_ASYM_PACKING - describes SMT quirks
> > + * SD_ASYM_CPUCAPACITY - describes mixed capacity topologies
> > */
>
> So I'm not sure the new CPUCAPACITY is 'odd'.
>
> That said, the comment is very terse and doesn't explain why PACKING is
> odd.
>
> IIRC the distinction is that the 'normal' ones only describe topology,
> while the ASYM_PACKING one also prescribes behaviour. It is odd in the
> way that it doesn't only describe things.
>
> This ASYM_CPUCAPACITY otoh is purely descriptive, it doesn't prescribe
> how to deal with it.
I think I initially put it in as an 'odd' flag due to the somewhat
strange semantics in the previous versions, but now that it is fixed I
agree that it belongs together with purely descriptive flags.
>
> Does something like so clarify things?
>
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -6355,13 +6355,19 @@ static int sched_domains_curr_level;
> /*
> * SD_flags allowed in topology descriptions.
> *
> - * SD_SHARE_CPUCAPACITY - describes SMT topologies
> - * SD_SHARE_PKG_RESOURCES - describes shared caches
> - * SD_NUMA - describes NUMA topologies
> - * SD_SHARE_POWERDOMAIN - describes shared power domain
> + * These flags are purely descriptive of the topology and do not prescribe
> + * behaviour. Behaviour is artificial and mapped in the below sd_init()
> + * function:
> *
> - * Odd one out:
> - * SD_ASYM_PACKING - describes SMT quirks
> + * SD_SHARE_CPUCAPACITY - describes SMT topologies
> + * SD_SHARE_PKG_RESOURCES - describes shared caches
> + * SD_NUMA - describes NUMA topologies
> + * SD_SHARE_POWERDOMAIN - describes shared power domain
> + *
> + * Odd one out, which beside describing the topology has a quirk also
> + * prescribes the desired behaviour that goes along with it:
> + *
> + * SD_ASYM_PACKING - describes SMT quirks
> */
> #define TOPOLOGY_SD_FLAGS \
> (SD_SHARE_CPUCAPACITY | \
I like it :)
Morten
next prev parent reply other threads:[~2016-08-15 11:43 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-07-25 13:34 [PATCH v3 00/13] sched: Clean-ups and asymmetric cpu capacity support Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 01/13] sched: Fix power to capacity renaming in comment Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 02/13] sched/fair: Consistent use of prev_cpu in wakeup path Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 03/13] sched/fair: Optimize find_idlest_cpu() when there is no choice Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 04/13] sched/core: Remove unnecessary null-pointer check Morten Rasmussen
2016-08-18 10:56 ` [tip:sched/core] sched/core: Remove unnecessary NULL-pointer check tip-bot for Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 05/13] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag Morten Rasmussen
2016-08-15 10:54 ` Peter Zijlstra
2016-08-15 11:43 ` Morten Rasmussen [this message]
2016-08-18 10:56 ` [tip:sched/core] sched/core: Clarify SD_flags comment tip-bot for Peter Zijlstra
2016-08-17 8:42 ` [PATCH v3 05/13] sched: Introduce SD_ASYM_CPUCAPACITY sched_domain topology flag Wanpeng Li
2016-08-17 9:23 ` Morten Rasmussen
2016-08-17 9:26 ` Wanpeng Li
2016-08-18 10:56 ` [tip:sched/core] sched/core: " tip-bot for Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 06/13] sched/core: Pass child domain into sd_init Morten Rasmussen
2016-08-18 10:57 ` [tip:sched/core] sched/core: Pass child domain into sd_init() tip-bot for Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 07/13] sched: Enable SD_BALANCE_WAKE for asymmetric capacity systems Morten Rasmussen
2016-08-18 10:57 ` [tip:sched/core] sched/core: " tip-bot for Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 08/13] sched: Store maximum per-cpu capacity in root domain Morten Rasmussen
2016-08-01 18:53 ` Dietmar Eggemann
2016-08-16 12:24 ` Vincent Guittot
2016-08-18 10:58 ` [tip:sched/core] sched/core: Store maximum per-CPU " tip-bot for Dietmar Eggemann
2016-07-25 13:34 ` [PATCH v3 09/13] sched/fair: Let asymmetric cpu configurations balance at wake-up Morten Rasmussen
2016-08-15 13:39 ` Peter Zijlstra
2016-08-15 15:01 ` Morten Rasmussen
2016-08-15 15:10 ` Peter Zijlstra
2016-08-15 15:30 ` Morten Rasmussen
2016-08-18 10:58 ` [tip:sched/core] sched/fair: Let asymmetric CPU " tip-bot for Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 10/13] sched/fair: Compute task/cpu utilization at wake-up more correctly Morten Rasmussen
2016-08-15 14:23 ` Peter Zijlstra
2016-08-15 15:42 ` Morten Rasmussen
2016-08-18 8:40 ` Morten Rasmussen
2016-08-18 10:24 ` Morten Rasmussen
2016-08-18 11:46 ` Wanpeng Li
2016-08-18 13:45 ` Morten Rasmussen
2016-08-19 1:43 ` Wanpeng Li
2016-08-19 14:03 ` Morten Rasmussen
2016-08-22 1:48 ` Wanpeng Li
2016-08-22 11:29 ` Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 11/13] sched/fair: Consider spare capacity in find_idlest_group() Morten Rasmussen
2016-08-16 13:57 ` Vincent Guittot
2016-08-18 11:16 ` Morten Rasmussen
2016-08-18 12:28 ` Peter Zijlstra
2016-07-25 13:34 ` [PATCH v3 12/13] sched: Add per-cpu min capacity to sched_group_capacity Morten Rasmussen
2016-07-25 13:34 ` [PATCH v3 13/13] sched/fair: Avoid pulling tasks from non-overloaded higher capacity groups Morten Rasmussen
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