Messages in this thread |  | | Subject | Re: [PATCH 3/4] mm, page_alloc: fix dirtyable highmem calculation | From | Vlastimil Babka <> | Date | Thu, 14 Jul 2016 17:22:25 +0200 |
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On 07/13/2016 12:00 PM, Mel Gorman wrote: > From: Minchan Kim <minchan@kernel.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@kernel.org> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Just some nitpicks:
> --- > mm/page-writeback.c | 16 ++++++++++------ > 1 file changed, 10 insertions(+), 6 deletions(-) > > diff --git a/mm/page-writeback.c b/mm/page-writeback.c > index 0bca2376bd42..7b41d1290783 100644 > --- a/mm/page-writeback.c > +++ b/mm/page-writeback.c > @@ -307,27 +307,31 @@ static unsigned long highmem_dirtyable_memory(unsigned long total) > { > #ifdef CONFIG_HIGHMEM > int node; > - unsigned long x = 0; > + unsigned long x; > int i; > - unsigned long dirtyable = atomic_read(&highmem_file_pages); > + unsigned long dirtyable = 0;
This wasn't necessary?
> > for_each_node_state(node, N_HIGH_MEMORY) { > for (i = ZONE_NORMAL + 1; i < MAX_NR_ZONES; i++) { > struct zone *z; > + unsigned long nr_pages; > > if (!is_highmem_idx(i)) > continue; > > z = &NODE_DATA(node)->node_zones[i]; > - dirtyable += zone_page_state(z, NR_FREE_PAGES); > + if (!populated_zone(z)) > + continue; > > + nr_pages = zone_page_state(z, NR_FREE_PAGES); > /* watch for underflows */ > - dirtyable -= min(dirtyable, high_wmark_pages(z)); > - > - x += dirtyable; > + nr_pages -= min(nr_pages, high_wmark_pages(z)); > + dirtyable += nr_pages; > } > } > > + x = dirtyable + atomic_read(&highmem_file_pages);
And then this addition wouldn't be necessary. BTW I think we could also ditch the "x" variable and just use the "dirtyable" for the rest of the function.
> + > /* > * Unreclaimable memory (kernel memory or anonymous memory > * without swap) can bring down the dirtyable pages below >
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