linux-kernel - Re: [PATCH RESEND v3] sched: Micro optimization in pick_next_task() and in check_preempt

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Message-ID: <20191220092631.GB2844@hirez.programming.kicks-ass.net>
Date:   Fri, 20 Dec 2019 10:26:31 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     ktkhai@...tuozzo.com
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "juri.lelli@...hat.com" <juri.lelli@...hat.com>,
        "vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
        "dietmar.eggemann@....com" <dietmar.eggemann@....com>,
        "bsegall@...gle.com" <bsegall@...gle.com>,
        Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH RESEND v3] sched: Micro optimization in pick_next_task()
 and in check_preempt_curr()

On Fri, Dec 20, 2019 at 12:27:05AM +0300, Kirill Tkhai wrote:
> This introduces an optimization based on xxx_sched_class addresses
> in two hot scheduler functions: pick_next_task() and check_preempt_curr().
> 
> It is possible to compare pointers to sched classes to check, which
> of them has a higher priority, instead of current iterations using
> for_each_class().
> 
> One more result of the patch is that size of object file becomes a little
> less (excluding added BUG_ON(), which goes in __init section):
> 
> $size kernel/sched/core.o
>          text     data      bss	    dec	    hex	filename
> before:  66446    18957	    676	  86079	  1503f	kernel/sched/core.o
> after:   66398    18957	    676	  86031	  1500f	kernel/sched/core.o
> 
> Signed-off-by: Kirill Tkhai <ktkhai@...tuozzo.com>

Thanks guys!