linux-kernel - Re: [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for the requested classzone

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Message-ID: <20160617120301.GM1868@techsingularity.net>
Date:	Fri, 17 Jun 2016 13:03:59 +0100
From:	Mel Gorman <mgorman@...hsingularity.net>
To:	Vlastimil Babka <vbabka@...e.cz>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Johannes Weiner <hannes@...xchg.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 21/27] mm, vmscan: Only wakeup kswapd once per node for
 the requested classzone

On Fri, Jun 17, 2016 at 12:46:05PM +0200, Vlastimil Babka wrote:
> On 06/09/2016 08:04 PM, Mel Gorman wrote:
> >kswapd is woken when zones are below the low watermark but the wakeup
> >decision is not taking the classzone into account.  Now that reclaim is
> >node-based, it is only required to wake kswapd once per node and only if
> >all zones are unbalanced for the requested classzone.
> >
> >Note that one node might be checked multiple times but there is no cheap
> >way of tracking what nodes have already been visited for zoneslists that
> >be ordered by either zone or node.
> 
> Wouldn't it be possible to optimize for node order as you did in direct
> reclaim? Do the zone_balanced checks when going through zonelist, and once
> node changes in iteration, wake up if no eligible zones visited so far were
> balanced.
> 

Yeah, it is. I'll chuck it in.

-- 
Mel Gorman
SUSE Labs