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

[Johannes Weiner]

On Wed, Jul 13, 2016 at 11:00:03AM +0100, Mel Gorman wrote:
> From: Minchan Kim <minchan@xxxxxxxxxx>
> 
> 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@xxxxxxxxxx>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>

Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>