On Wed 12-08-15 11:45:28, Mel Gorman wrote:
> File-backed pages that will be immediately are balanced between zones but
^written to...
> it's unnecessarily expensive.
to do WHAT? I guess you meant checking gfp_mask resp. alloc_mask? I
doubt it would make a noticeable difference as this is a slow path
already but I agree it doesn't make sense to check it again.
> Move consider_zone_balanced into the alloc_context
> instead of checking bitmaps multiple times. The patch also gives the parameter
> a more meaningful name.
>
> Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
> Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> ---
> mm/internal.h | 1 +
> mm/page_alloc.c | 11 +++++++----
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/mm/internal.h b/mm/internal.h
> index 36b23f1e2ca6..9331f802a067 100644
> --- a/mm/internal.h
> +++ b/mm/internal.h
> @@ -129,6 +129,7 @@ struct alloc_context {
> int classzone_idx;
> int migratetype;
> enum zone_type high_zoneidx;
> + bool spread_dirty_pages;
> };
>
> /*
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 5e1f6f4370bc..94f2f6bdd6d5 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2297,8 +2297,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> struct zoneref *z;
> struct page *page = NULL;
> struct zone *zone;
> - bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
> - (gfp_mask & __GFP_WRITE);
> int nr_fair_skipped = 0;
> bool zonelist_rescan;
>
> @@ -2350,14 +2348,14 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
> *
> * XXX: For now, allow allocations to potentially
> * exceed the per-zone dirty limit in the slowpath
> - * (ALLOC_WMARK_LOW unset) before going into reclaim,
> + * (spread_dirty_pages unset) before going into reclaim,
> * which is important when on a NUMA setup the allowed
> * zones are together not big enough to reach the
> * global limit. The proper fix for these situations
> * will require awareness of zones in the
> * dirty-throttling and the flusher threads.
> */
> - if (consider_zone_dirty && !zone_dirty_ok(zone))
> + if (ac->spread_dirty_pages && !zone_dirty_ok(zone))
> continue;
>
> mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
> @@ -2997,6 +2995,10 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
>
> /* We set it here, as __alloc_pages_slowpath might have changed it */
> ac.zonelist = zonelist;
> +
> + /* Dirty zone balancing only done in the fast path */
> + ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);
> +
> /* The preferred zone is used for statistics later */
> preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx,
> ac.nodemask, &ac.preferred_zone);
> @@ -3014,6 +3016,7 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order,
> * complete.
> */
> alloc_mask = memalloc_noio_flags(gfp_mask);
> + ac.spread_dirty_pages = false;
>
> page = __alloc_pages_slowpath(alloc_mask, order, &ac);
> }
> --
> 2.4.6
>
> --
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--
Michal Hocko
SUSE Labs
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