linux-kernel - Re: [PATCH -tip-rcu] Make rcutorture more vicious: make quiescent rcutorture less power-hungry

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Date:	Sun, 22 Jun 2008 13:17:12 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu, josh@...edesktop.org,
	dvhltc@...ibm.com, niv@...ibm.com, dino@...ibm.com,
	akpm@...ux-foundation.org, torvalds@...ux-foundation.org,
	vegard.nossum@...il.com, adobriyan@...il.com, oleg@...sign.ru,
	bunk@...nel.org, rjw@...k.pl
Subject: Re: [PATCH -tip-rcu] Make rcutorture more vicious: make quiescent
 rcutorture less power-hungry

On Sun, 22 Jun 2008 13:06:38 -0700
"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> wrote:

> This patch makes the non-module rcutorture a bit more friendly to
> the power-conservation code.  This is a rather simple-minded approach.
> More sophisticated approaches would get rid of the rcutorture tasks
> while rcutorture execution was suppressed, but attempts thus far to
> do this have not gone well -- calling rcu_torture_init() from a /proc
> callout results in oopses.
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
> ---
> 
>  rcutorture.c |    5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff -urpNa -X dontdiff
> linux-2.6.26-rc4-rcut2-proc/kernel/rcutorture.c
> linux-2.6.26-rc4-rcut3-procq/kernel/rcutorture.c ---
> linux-2.6.26-rc4-rcut2-proc/kernel/rcutorture.c	2008-06-22
> 10:29:04.000000000 -0700 +++
> linux-2.6.26-rc4-rcut3-procq/kernel/rcutorture.c	2008-06-22
> 12:20:10.000000000 -0700 @@ -196,7 +196,10 @@ static void
> rcu_stutter_wait(void) { while (stutter_pause_test
> || !rcutorture_runnable)
> -		schedule_timeout_interruptible(1);
> +		if (rcutorture_runnable)
> +			schedule_timeout_interruptible(1);
> +		else
> +			schedule_timeout_interruptible(HZ);
>  }

could you also make it use round_jiffies_relative() to make the power
impact even less.....
(by coalescing various "once a second" timers like this)



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