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Date: Thu, 19 Oct 2006 13:40:46 -0700
From: "Siddha, Suresh B" <suresh.b.siddha@intel.com>
To: Christoph Lameter <clameter@sgi.com>
Cc: "Siddha, Suresh B" <suresh.b.siddha@intel.com>,
       Nick Piggin <nickpiggin@yahoo.com.au>, Ingo Molnar <mingo@elte.hu>,
       Peter Williams <pwil3058@bigpond.net.au>, linux-kernel@vger.kernel.org
Subject: Re: [RFC] sched_tick with interrupts enabled
Message-ID: <20061019134046.A2305@unix-os.sc.intel.com>
References: <Pine.LNX.4.64.0610181001480.28582@schroedinger.engr.sgi.com> <4536629C.4050807@yahoo.com.au> <Pine.LNX.4.64.0610181059570.28750@schroedinger.engr.sgi.com> <45366DF0.6040702@yahoo.com.au> <Pine.LNX.4.64.0610181145250.29163@schroedinger.engr.sgi.com> <45367D32.6090301@yahoo.com.au> <Pine.LNX.4.64.0610181457130.30795@schroedinger.engr.sgi.com> <20061018191900.D26521@unix-os.sc.intel.com> <Pine.LNX.4.64.0610190736210.7337@schroedinger.engr.sgi.com>
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In-Reply-To: <Pine.LNX.4.64.0610190736210.7337@schroedinger.engr.sgi.com>; from clameter@sgi.com on Thu, Oct 19, 2006 at 08:50:50AM -0700
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On Thu, Oct 19, 2006 at 08:50:50AM -0700, Christoph Lameter wrote:
> Ok. Thanks. Would this work?
> 
> Index: linux-2.6.19-rc2-mm1/kernel/sched.c
> ===================================================================
> --- linux-2.6.19-rc2-mm1.orig/kernel/sched.c	2006-10-19 09:39:08.000000000 -0500
> +++ linux-2.6.19-rc2-mm1/kernel/sched.c	2006-10-19 09:42:10.733631242 -0500
> @@ -2846,7 +2846,8 @@ static void rebalance_tick(unsigned long
>  	struct sched_domain *sd;
>  	int i, scale;
>  
> -	idle = (current == this_rq->idle) ? SCHED_IDLE : NOT_IDLE;
> +	idle = (current == this_rq->idle && !this_rq->nr_running) ?
> +				SCHED_IDLE : NOT_IDLE;

A comment of why we are checking for nr_running would be nice.

And one more thing. We can reduce some of the tasklet invoking complexity
by actually checking for a load_balance() need at any domain and thus
invoking tasklet which will do the load balance, rather than unconditionally
invoking tasklet for each tick.

thanks,
suresh