Date: Mon, 23 Feb 2015 15:25:14 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Rik van Riel <riel@redhat.com>, Mel Gorman <mgorman@suse.de>,
        Michal Hocko <mhocko@suse.cz>,
        Ebru Akagunduz <ebru.akagunduz@gmail.com>,
        Alex Thorlton <athorlton@sgi.com>,
        David Rientjes <rientjes@google.com>, Ingo Molnar <mingo@kernel.org>
Subject: Re: [RFC 4/6] mm, thp: move collapsing from khugepaged to task_work
 context
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On Mon, Feb 23, 2015 at 01:58:40PM +0100, Vlastimil Babka wrote:
> @@ -7713,8 +7820,15 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
>  		entity_tick(cfs_rq, se, queued);
>  	}
>  
> -	if (numabalancing_enabled)
> -		task_tick_numa(rq, curr);
> +	/*
> +	 * For latency considerations, don't schedule the THP work together
> +	 * with NUMA work. NUMA has higher priority, assuming remote accesses
> +	 * have worse penalty than TLB misses.
> +	 */
> +	if (!(numabalancing_enabled && task_tick_numa(rq, curr))
> +						&& khugepaged_enabled())
> +		task_tick_thp(rq, curr);
> +
>  
>  	update_rq_runnable_avg(rq, 1);
>  }

That's a bit yucky; and I think there's no problem moving that
update_rq_runnable_avg() thing up a bit; which would get you:

static void task_tick_fair(..)
{

	...

	update_rq_runnable_avg();

	if (numabalancing_enabled && task_tick_numa(rq, curr))
		return;

	if (khugepaged_enabled() && task_tick_thp(rq, curr))
		return;
}

Clearly the return on that second conditional is a tad pointless, but
OCD :-)
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