linux-kernel - Re: [PATCH 12/34] mm: vmscan: do not reclaim from kswapd if there is any eligible zone

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Message-ID: <20160713122848.GA9905@cmpxchg.org>
Date:	Wed, 13 Jul 2016 08:28:48 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Mel Gorman <mgorman@...hsingularity.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Linux-MM <linux-mm@...ck.org>, Rik van Riel <riel@...riel.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Minchan Kim <minchan@...nel.org>,
	Joonsoo Kim <iamjoonsoo.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 12/34] mm: vmscan: do not reclaim from kswapd if there is
 any eligible zone

On Wed, Jul 13, 2016 at 09:47:42AM +0100, Mel Gorman wrote:
> On Tue, Jul 12, 2016 at 10:29:09AM -0400, Johannes Weiner wrote:
> > > +		/*
> > > +		 * If the number of buffer_heads in the machine exceeds the
> > > +		 * maximum allowed level then reclaim from all zones. This is
> > > +		 * not specific to highmem as highmem may not exist but it is
> > > +		 * it is expected that buffer_heads are stripped in writeback.
> > 
> > The mention of highmem in this comment make only sense within the
> > context of this diff; it'll be pretty confusing in the standalone
> > code.
> > 
> > Also, double "it is" :)
> 
> Is this any better?

Yes, this is great! Thank you.

> Note that it's marked as a fix to a later patch to reduce collisions in
> mmotm. It's not a bisection risk so I saw little need to cause
> unnecessary conflicts for Andrew.

That seems completely reasonable to me.

> ---8<---
> mm, vmscan: Have kswapd reclaim from all zones if reclaiming and buffer_heads_over_limit -fix
> 
> Johannes reported that the comment about buffer_heads_over_limit in
> balance_pgdat only made sense in the context of the patch. This
> patch clarifies the reasoning and how it applies to 32 and 64 bit
> systems.
> 
> This is a fix to the mmotm patch
> mm-vmscan-have-kswapd-reclaim-from-all-zones-if-reclaiming-and-buffer_heads_over_limit.patch
> 
> Suggested-by: Johannes Weiner <hannes@...xchg.org>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

Acked-by: Johannes Weiner <hannes@...xchg.org>