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Date: Thu, 4 Jul 2013 17:56:44 +0530
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Mel Gorman <mgorman@suse.de>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@kernel.org>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>, Linux-MM <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 06/13] sched: Reschedule task on preferred NUMA node once
 selected
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Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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* Mel Gorman <mgorman@suse.de> [2013-07-03 15:21:33]:

> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 2a0bbc2..b9139be 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -800,6 +800,37 @@ unsigned int sysctl_numa_balancing_scan_delay = 1000;
>   */
>  unsigned int sysctl_numa_balancing_settle_count __read_mostly = 3;
> 
> +static unsigned long weighted_cpuload(const int cpu);
> +
> +static int
> +find_idlest_cpu_node(int this_cpu, int nid)
> +{
> +	unsigned long load, min_load = ULONG_MAX;
> +	int i, idlest_cpu = this_cpu;
> +
> +	BUG_ON(cpu_to_node(this_cpu) == nid);
> +
> +	for_each_cpu(i, cpumask_of_node(nid)) {
> +		load = weighted_cpuload(i);
> +
> +		if (load < min_load) {
> +			struct task_struct *p;
> +
> +			/* Do not preempt a task running on its preferred node */
> +			struct rq *rq = cpu_rq(i);
> +			raw_spin_lock_irq(&rq->lock);

Not sure why we need this spin_lock? Cant this be done in a rcu block
instead?


-- 
Thanks and Regards
Srikar Dronamraju