linux-kernel - Re: [patch 2/3] sched: fix minimum power returned by update_cpu

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Message-ID: <1281945037.1926.954.camel@laptop>
Date:	Mon, 16 Aug 2010 09:50:37 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
Cc:	mingo@...e.hu, linux-kernel@...r.kernel.org, chris@...stnet.net,
	debian00@...ceadsl.fr, hpa@...or.com, jonathan.protzenko@...il.com,
	mans@...sr.com, psastudio@...l.ru, rjw@...k.pl,
	stephan.eicher@....de, sxxe@....de, thomas@...hlinux.org,
	venki@...gle.com, wonghow@...il.com
Subject: Re: [patch 2/3] sched: fix minimum power returned by
 update_cpu_power()

On Fri, 2010-08-13 at 12:45 -0700, Suresh Siddha wrote:
> plain text document attachment (fix_update_cpu_power.patch)
> Default cpu_power needs to be multiples of SCHED_LOAD_SCALE and not '1'.
> Fix it.
> 
> Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
> ---
>  kernel/sched_fair.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Index: tree/kernel/sched_fair.c
> ===================================================================
> --- tree.orig/kernel/sched_fair.c
> +++ tree/kernel/sched_fair.c
> @@ -2309,7 +2309,7 @@ static void update_cpu_power(struct sche
>  	power >>= SCHED_LOAD_SHIFT;
>  
>  	if (!power)
> -		power = 1;
> +		power = SCHED_LOAD_SCALE;
>  

                            smt_power   freq_power    rt_power
power = SCHED_LOAD_SCALE * ---------- * ---------- * ----------
                           LOAD_SCALE   LOAD_SCALE   LOAD_SCALE

Which, in the above case ends up being 0, so how does resetting it back
to LOAD_SCALE make sense?
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