From: Peter Zijlstra <peterz@infradead.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
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 06/15] sched: Reschedule task on preferred NUMA node once selected
Date: Sat, 6 Jul 2013 12:38:13 +0200 [thread overview]
Message-ID: <20130706103813.GQ18898@dyad.programming.kicks-ass.net> (raw)
In-Reply-To: <1373065742-9753-7-git-send-email-mgorman@suse.de>
On Sat, Jul 06, 2013 at 12:08:53AM +0100, Mel Gorman wrote:
> +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);
> +
> + rcu_read_lock();
> + for_each_cpu(i, cpumask_of_node(nid)) {
> + load = weighted_cpuload(i);
> +
> + if (load < min_load) {
> + /*
> + * Kernel threads can be preempted. For others, do
> + * not preempt if running on their preferred node
> + * or pinned.
> + */
> + struct task_struct *p = cpu_rq(i)->curr;
> + if ((p->flags & PF_KTHREAD) ||
> + (p->numa_preferred_nid != nid && p->nr_cpus_allowed > 1)) {
> + min_load = load;
> + idlest_cpu = i;
> + }
So I really don't get this stuff.. if it is indeed the idlest cpu preempting
others shouldn't matter. Also, migrating a task there doesn't actually mean it
will get preempted either.
In overloaded scenarios it expected that multiple tasks will run on the same
cpu. So this condition will also explicitly make overloaded scenarios work less
well.
> + }
> + }
> + rcu_read_unlock();
> +
> + return idlest_cpu;
> +}
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next prev parent reply other threads:[~2013-07-06 10:39 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-07-05 23:08 [PATCH 0/15] Basic scheduler support for automatic NUMA balancing V3 Mel Gorman
2013-07-05 23:08 ` [PATCH 01/15] mm: numa: Document automatic NUMA balancing sysctls Mel Gorman
2013-07-05 23:08 ` [PATCH 02/15] sched: Track NUMA hinting faults on per-node basis Mel Gorman
2013-07-05 23:08 ` [PATCH 03/15] sched: Select a preferred node with the most numa hinting faults Mel Gorman
2013-07-05 23:08 ` [PATCH 04/15] sched: Update NUMA hinting faults once per scan Mel Gorman
2013-07-05 23:08 ` [PATCH 05/15] sched: Favour moving tasks towards the preferred node Mel Gorman
2013-07-05 23:08 ` [PATCH 06/15] sched: Reschedule task on preferred NUMA node once selected Mel Gorman
2013-07-06 10:38 ` Peter Zijlstra [this message]
2013-07-08 8:34 ` Mel Gorman
2013-07-05 23:08 ` [PATCH 07/15] sched: Add infrastructure for split shared/private accounting of NUMA hinting faults Mel Gorman
2013-07-05 23:08 ` [PATCH 08/15] sched: Increase NUMA PTE scanning when a new preferred node is selected Mel Gorman
2013-07-05 23:08 ` [PATCH 09/15] sched: Check current->mm before allocating NUMA faults Mel Gorman
2013-07-05 23:08 ` [PATCH 10/15] sched: Set the scan rate proportional to the size of the task being scanned Mel Gorman
2013-07-05 23:08 ` [PATCH 11/15] mm: numa: Scan pages with elevated page_mapcount Mel Gorman
2013-07-05 23:08 ` [PATCH 12/15] sched: Remove check that skips small VMAs Mel Gorman
2013-07-05 23:09 ` [PATCH 13/15] sched: Set preferred NUMA node based on number of private faults Mel Gorman
2013-07-06 10:41 ` Peter Zijlstra
2013-07-08 9:23 ` Mel Gorman
2013-07-06 10:44 ` Peter Zijlstra
2013-07-05 23:09 ` [PATCH 14/15] sched: Account for the number of preferred tasks running on a node when selecting a preferred node Mel Gorman
2013-07-06 10:46 ` Peter Zijlstra
2013-07-05 23:09 ` [PATCH 15/15] sched: Favour moving tasks towards nodes that incurred more faults Mel Gorman
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