mm, page_alloc: remove unnecessary recalculations for dirty zone balancing
File-backed pages that will be immediately written are balanced between zones. This heuristic tries to avoid having a single zone filled with recently dirtied pages but the checks are unnecessarily expensive. 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@techsingularity.net> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Vlastimil Babka <vbabka@suse.cz> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Christoph Lameter <cl@linux.com> Cc: Vitaly Wool <vitalywool@gmail.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -129,6 +129,7 @@ struct alloc_context {
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int classzone_idx;
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int migratetype;
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enum zone_type high_zoneidx;
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bool spread_dirty_pages;
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};
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/*
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@ -2478,8 +2478,6 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
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nodemask_t *allowednodes = NULL;/* zonelist_cache approximation */
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int zlc_active = 0; /* set if using zonelist_cache */
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int did_zlc_setup = 0; /* just call zlc_setup() one time */
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bool consider_zone_dirty = (alloc_flags & ALLOC_WMARK_LOW) &&
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(gfp_mask & __GFP_WRITE);
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int nr_fair_skipped = 0;
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bool zonelist_rescan;
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@ -2534,14 +2532,14 @@ zonelist_scan:
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*
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* XXX: For now, allow allocations to potentially
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* exceed the per-zone dirty limit in the slowpath
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* (ALLOC_WMARK_LOW unset) before going into reclaim,
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* (spread_dirty_pages unset) before going into reclaim,
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* which is important when on a NUMA setup the allowed
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* zones are together not big enough to reach the
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* global limit. The proper fix for these situations
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* will require awareness of zones in the
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* dirty-throttling and the flusher threads.
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*/
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if (consider_zone_dirty && !zone_dirty_ok(zone))
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if (ac->spread_dirty_pages && !zone_dirty_ok(zone))
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continue;
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mark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK];
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@ -3232,6 +3230,10 @@ retry_cpuset:
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/* We set it here, as __alloc_pages_slowpath might have changed it */
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ac.zonelist = zonelist;
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/* Dirty zone balancing only done in the fast path */
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ac.spread_dirty_pages = (gfp_mask & __GFP_WRITE);
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/* The preferred zone is used for statistics later */
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preferred_zoneref = first_zones_zonelist(ac.zonelist, ac.high_zoneidx,
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ac.nodemask ? : &cpuset_current_mems_allowed,
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@ -3250,6 +3252,7 @@ retry_cpuset:
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* complete.
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*/
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alloc_mask = memalloc_noio_flags(gfp_mask);
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ac.spread_dirty_pages = false;
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page = __alloc_pages_slowpath(alloc_mask, order, &ac);
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}
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