linux-kernel - Re: [PATCH 3/4] mm, page_alloc: fix dirtyable highmem calculation

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Message-ID: <20160713131555.GE9905@cmpxchg.org>
Date:	Wed, 13 Jul 2016 09:15:55 -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>, Minchan Kim <minchan@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/4] mm, page_alloc: fix dirtyable highmem calculation

On Wed, Jul 13, 2016 at 11:00:03AM +0100, Mel Gorman wrote:
> From: Minchan Kim <minchan@...nel.org>
> 
> Note from Mel: This may optionally be considered a fix to the mmotm patch
> 	mm-page_alloc-consider-dirtyable-memory-in-terms-of-nodes.patch
> 	but if so, please preserve credit for Minchan.
> 
> When I tested vmscale in mmtest in 32bit, I found the benchmark was slow
> down 0.5 times.
> 
>                 base        node
>                    1    global-1
> User           12.98       16.04
> System        147.61      166.42
> Elapsed        26.48       38.08
> 
> With vmstat, I found IO wait avg is much increased compared to base.
> 
> The reason was highmem_dirtyable_memory accumulates free pages and
> highmem_file_pages from HIGHMEM to MOVABLE zones which was wrong. With
> that, dirth_thresh in throtlle_vm_write is always 0 so that it calls
> congestion_wait frequently if writeback starts.
> 
> With this patch, it is much recovered.
> 
>                 base        node          fi
>                    1    global-1         fix
> User           12.98       16.04       13.78
> System        147.61      166.42      143.92
> Elapsed        26.48       38.08       29.64
> 
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> Signed-off-by: Mel Gorman <mgorman@...hsingularity.net>

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