linux-kernel - Re: [PATCH 11/31] mm: vmscan: do not reclaim from kswapd if there is any eligible zone

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Date:	Thu, 7 Jul 2016 11:55:16 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 11/31] mm: vmscan: do not reclaim from kswapd if there is
 any eligible zone

On Thu, Jul 07, 2016 at 03:27:01PM +0900, Minchan Kim wrote:
> > I'm not going to go with it for now because buffer_heads_over_limit is not
> > necessarily a problem unless lowmem is factor. We don't want background
> > reclaim to go ahead unnecessarily just because buffer_heads_over_limit.
> > It could be distinguished by only forcing reclaim to go ahead on systems
> > with highmem.
> 
> If you don't think it's a problem, I don't want to insist on it because I don't
> have any report/workload right now. Instead, please write some comment in there
> for others to understand why kswapd is okay to ignore buffer_heads_over_limit
> unlike direct reclaim. Such non-symmetric behavior is really hard to follow
> without any description.

Ok, I'll add a patch later in the series that addresses the issue.
Currently it's called "mm, vmscan: Have kswapd reclaim from all zones if
reclaiming and buffer_heads_over_limit".

-- 
Mel Gorman
SUSE Labs