linux-kernel - Re: [PATCH v3 0/3] sched/fair: Simplify and optimize update_sd_pick

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Message-ID: <20240216194440.GA1682@maniforge>
Date: Fri, 16 Feb 2024 13:44:40 -0600
From: David Vernet <void@...ifault.com>
To: peterz@...radead.org
Cc: mingo@...hat.com, linux-kernel@...r.kernel.org, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	bsegall@...gle.com, bristot@...hat.com, vschneid@...hat.com,
	kernel-team@...a.com
Subject: Re: [PATCH v3 0/3] sched/fair: Simplify and optimize
 update_sd_pick_busiest()

On Mon, Feb 05, 2024 at 10:39:18PM -0600, David Vernet wrote:
> update_sd_pick_busiest() (and its caller) has some room for small
> optimizations, and some improvements in readability.

Hello Peter, hello Ingo,

Friendly ping. Is there anything else required for this to land?

Thanks,
David

> 
> - In update_sd_lb_stats(), we're using a goto to skip a single if check.
>   Let's remove the goto and just add another condition to the if.
> 
> - In update_sd_pick_busiest(), only update a group_misfit_task group to
>   be the busiest if it has strictly more load than the current busiest
>   task, rather than >= the load.
> 
> - When comparing the current struct sched_group with the yet-busiest
>   domain in update_sd_pick_busiest(), if the two groups have the same
>   group type, we're currently doing a bit of unnecessary work for any
>   group >= group_misfit_task. We're comparing the two groups, and then
>   returning only if false (the group in question is not the busiest).
>   Othewise, we break, do an extra unnecessary conditional check that's
>   vacuously false for any group type > group_fully_busy, and then always
>   return true. This patch series has us instead simply return directly
>   in the switch statement, saving some bytes in load_balance().
> 
> ---
> 
> v1: https://lore.kernel.org/lkml/20240202070216.2238392-1-void@manifault.com/
> v2: https://lore.kernel.org/all/20240204044618.46100-1-void@manifault.com/
> 
> v2 -> v3:
> - Add Vincent's Reviewed-by tags
> - Fix stale commit summary sentence (Vincent)
> 
> v1 -> v2 changes:
> 
> - Split the patch series into separate patches (Valentin)
> - Update the group_misfit_task busiest check to use strict inequality
> 
> David Vernet (3):
>   sched/fair: Remove unnecessary goto in update_sd_lb_stats()
>   sched/fair: Do strict inequality check for busiest misfit task group
>   sched/fair: Simplify some logic in update_sd_pick_busiest()
> 
>  kernel/sched/fair.c | 19 ++++---------------
>  1 file changed, 4 insertions(+), 15 deletions(-)
> 
> -- 
> 2.43.0
> 

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