mm, vmscan: avoid passing in classzone_idx unnecessarily to compaction_ready

The scan_control structure has enough information available for
compaction_ready() to make a decision.  The classzone_idx manipulations
in shrink_zones() are no longer necessary as the highest populated zone
is no longer used to determine if shrink_slab should be called or not.

[mgorman@techsingularity.net remove redundant check in shrink_zones()]
Link: http://lkml.kernel.org/r/1468588165-12461-3-git-send-email-mgorman@techsingularity.net
Link: http://lkml.kernel.org/r/1467970510-21195-26-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 7bfc0fe..a9bd8b2 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2523,7 +2523,7 @@ static bool shrink_node(pg_data_t *pgdat, struct scan_control *sc)
  * Returns true if compaction should go ahead for a high-order request, or
  * the high-order allocation would succeed without compaction.
  */
-static inline bool compaction_ready(struct zone *zone, int order, int classzone_idx)
+static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 {
        unsigned long watermark;
        bool watermark_ok;
@@ -2534,21 +2534,21 @@ static inline bool compaction_ready(struct zone *zone, int order, int classzone_
         * there is a buffer of free pages available to give compaction
         * a reasonable chance of completing and allocating the page
         */
-       watermark = high_wmark_pages(zone) + (2UL << order);
-       watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, classzone_idx);
+       watermark = high_wmark_pages(zone) + (2UL << sc->order);
+       watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, sc->reclaim_idx);
 
        /*
         * If compaction is deferred, reclaim up to a point where
         * compaction will have a chance of success when re-enabled
         */
-       if (compaction_deferred(zone, order))
+       if (compaction_deferred(zone, sc->order))
                return watermark_ok;
 
        /*
         * If compaction is not ready to start and allocation is not likely
         * to succeed without it, then keep reclaiming.
         */
-       if (compaction_suitable(zone, order, 0, classzone_idx) == COMPACT_SKIPPED)
+       if (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx) == COMPACT_SKIPPED)
                return false;
 
        return watermark_ok;
@@ -2569,7 +2569,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
        unsigned long nr_soft_reclaimed;
        unsigned long nr_soft_scanned;
        gfp_t orig_mask;
-       enum zone_type classzone_idx;
        pg_data_t *last_pgdat = NULL;
 
        /*
@@ -2580,7 +2579,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
        orig_mask = sc->gfp_mask;
        if (buffer_heads_over_limit) {
                sc->gfp_mask |= __GFP_HIGHMEM;
-               sc->reclaim_idx = classzone_idx = gfp_zone(sc->gfp_mask);
+               sc->reclaim_idx = gfp_zone(sc->gfp_mask);
        }
 
        for_each_zone_zonelist_nodemask(zone, z, zonelist,
@@ -2589,17 +2588,6 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
                        continue;
 
                /*
-                * Note that reclaim_idx does not change as it is the highest
-                * zone reclaimed from which for empty zones is a no-op but
-                * classzone_idx is used by shrink_node to test if the slabs
-                * should be shrunk on a given node.
-                */
-               classzone_idx = sc->reclaim_idx;
-               while (!populated_zone(zone->zone_pgdat->node_zones +
-                                                       classzone_idx))
-                       classzone_idx--;
-
-               /*
                 * Take care memory controller reclaiming has small influence
                 * to global LRU.
                 */
@@ -2623,8 +2611,7 @@ static void shrink_zones(struct zonelist *zonelist, struct scan_control *sc)
                         */
                        if (IS_ENABLED(CONFIG_COMPACTION) &&
                            sc->order > PAGE_ALLOC_COSTLY_ORDER &&
-                           zonelist_zone_idx(z) <= classzone_idx &&
-                           compaction_ready(zone, sc->order, classzone_idx)) {
+                           compaction_ready(zone, sc)) {
                                sc->compaction_ready = true;
                                continue;
                        }