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From: Valentin Schneider <valentin.schneider@arm.com>
To: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: linux-kernel@vger.kernel.org, mingo@kernel.org,
	peterz@infradead.org, vincent.guittot@linaro.org
Subject: Re: [PATCH v2 4/9] sched/topology: Kill SD_LOAD_BALANCE
Date: Thu, 19 Mar 2020 12:06:07 +0000	[thread overview]
Message-ID: <jhjtv2ko8gg.mognet@arm.com> (raw)
In-Reply-To: <a4a87ce6-9770-dc58-c2b6-e001b8050a8e@arm.com>


On Thu, Mar 19 2020, Dietmar Eggemann wrote:
> On 11.03.20 19:15, Valentin Schneider wrote:
>> That flag is set unconditionally in sd_init(), and no one checks for it
>> anymore. Remove it.
>
> Why not merge 3/9 and 4/9 ?
>
> [...]
>
>> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
>> index f341163fedc9..8de2f9744569 100644
>> --- a/include/linux/sched/topology.h
>> +++ b/include/linux/sched/topology.h
>> @@ -11,21 +11,20 @@
>>   */
>>  #ifdef CONFIG_SMP
>>
>> -#define SD_LOAD_BALANCE		0x0001	/* Do load balancing on this domain. */
>> -#define SD_BALANCE_NEWIDLE	0x0002	/* Balance when about to become idle */
>
> [...]
>
>> -#define SD_OVERLAP		0x2000	/* sched_domains of this level overlap */
>> -#define SD_NUMA			0x4000	/* cross-node balancing */
>> +#define SD_BALANCE_NEWIDLE	0x0001	/* Balance when about to become idle */
>
> IMHO, changing the values of the remaining SD flags will break lots of
> userspace scripts.
>

True, and that includes some of my own scripts. That's also part of why
I have this 3/9 and 4/9 split: 4/9 is the externally visible part. If
deemed necessary, we could keep the definition of SD_LOAD_BALANCE but
kill all of its uses.

Alternatively, I was thinking that we could leverage [1] to make
/proc/sys/kernel/sched_domain/cpu*/domain*/flags print
e.g. comma-separated flag names rather than flag values. That way the
userland scripts would no longer have to contain some
{flag_value : flag_name} translation.

[1]: https://lkml.kernel.org/r/20200311183320.19186-1-valentin.schneider@arm.com

> [...]

  reply	other threads:[~2020-03-19 12:06 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-11 18:15 [PATCH v2 0/9] sched: Streamline select_task_rq() & select_task_rq_fair() Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 1/9] sched/fair: find_idlest_group(): Remove unused sd_flag parameter Valentin Schneider
2020-03-19  9:05   ` Dietmar Eggemann
2020-03-11 18:15 ` [PATCH v2 2/9] sched/debug: Make sd->flags sysctl read-only Valentin Schneider
2020-03-19  9:07   ` Dietmar Eggemann
2020-03-19 12:04     ` Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 3/9] sched: Remove checks against SD_LOAD_BALANCE Valentin Schneider
2020-03-19 10:28   ` Dietmar Eggemann
2020-03-19 12:05     ` Valentin Schneider
2020-03-23 14:26       ` Dietmar Eggemann
2020-03-23 17:17         ` Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 4/9] sched/topology: Kill SD_LOAD_BALANCE Valentin Schneider
2020-03-19 10:29   ` Dietmar Eggemann
2020-03-19 12:06     ` Valentin Schneider [this message]
2020-03-11 18:15 ` [PATCH v2 5/9] sched: Add WF_TTWU, WF_EXEC wakeup flags Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 6/9] sched: Kill select_task_rq()'s sd_flag parameter Valentin Schneider
2020-03-11 18:15 ` [PATCH v2 7/9] sched/fair: Dissociate wakeup decisions from SD flag value Valentin Schneider
2020-03-11 18:16 ` [PATCH v2 8/9] sched/fair: Split select_task_rq_fair want_affine logic Valentin Schneider
2020-03-19 10:30   ` Dietmar Eggemann
2020-03-19 12:06     ` Valentin Schneider
2020-03-11 18:16 ` [PATCH v2 9/9] sched/topology: Define and use shortcut pointers for wakeup sd_flag scan Valentin Schneider
2020-03-19 10:46   ` Dietmar Eggemann
2020-03-19 12:22     ` Valentin Schneider

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