linux-kernel - RE: [patch 3/7] mm: vmscan: clarify how swappiness, highest priority, memcg interact

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Date:	Mon, 17 Dec 2012 19:37:55 +0000
From:	Satoru Moriya <satoru.moriya@....com>
To:	Johannes Weiner <hannes@...xchg.org>,
	Andrew Morton <akpm@...ux-foundation.org>
CC:	Rik van Riel <riel@...hat.com>, Michal Hocko <mhocko@...e.cz>,
	Mel Gorman <mgorman@...e.de>, Hugh Dickins <hughd@...gle.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [patch 3/7] mm: vmscan: clarify how swappiness, highest
 priority, memcg interact

On 12/17/2012 01:12 PM, Johannes Weiner wrote:
> A swappiness of 0 has a slightly different meaning for global reclaim 
> (may swap if file cache really low) and memory cgroup reclaim (never 
> swap, ever).
> 
> In addition, global reclaim at highest priority will scan all LRU 
> lists equal to their size and ignore other balancing heuristics.
> UNLESS swappiness forbids swapping, then the lists are balanced based 
> on recent reclaim effectiveness.  UNLESS file cache is running low, 
> then anonymous pages are force-scanned.
> 
> This (total mess of a) behaviour is implicit and not obvious from the 
> way the code is organized.  At least make it apparent in the code flow 
> and document the conditions.  It will be it easier to come up with 
> sane semantics later.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Reviewed-by: Satoru Moriya <satoru.moriya@....com>

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