linux-kernel - Re: [PATCH 09/10] mm: only count actual rotations as LRU reclaim cost

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Message-ID: <20160608081903.GE28620@bbox>
Date:	Wed, 8 Jun 2016 17:19:03 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Johannes Weiner <hannes@...xchg.org>
CC:	<linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rik van Riel <riel@...hat.com>, Mel Gorman <mgorman@...e.de>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Andi Kleen <andi@...stfloor.org>,
	Michal Hocko <mhocko@...e.cz>,
	Tim Chen <tim.c.chen@...ux.intel.com>, <kernel-team@...com>
Subject: Re: [PATCH 09/10] mm: only count actual rotations as LRU reclaim cost

On Mon, Jun 06, 2016 at 03:48:35PM -0400, Johannes Weiner wrote:
> Noting a reference on an active file page but still deactivating it
> represents a smaller cost of reclaim than noting a referenced
> anonymous page and actually physically rotating it back to the head.
> The file page *might* refault later on, but it's definite progress
> toward freeing pages, whereas rotating the anonymous page costs us
> real time without making progress toward the reclaim goal.
> 
> Don't treat both events as equal. The following patch will hook up LRU
> balancing to cache and swap refaults, which are a much more concrete
> cost signal for reclaiming one list over the other. Remove the
> maybe-IO cost bias from page references, and only note the CPU cost
> for actual rotations that prevent the pages from getting reclaimed.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>
Acked-by: Minchan Kim <minchan@...nel.org>