mm: compaction: refactor __compaction_suitable()

__compaction_suitable() is supposed to check for available migration
targets.  However, it also checks whether the operation was requested via
/proc/sys/vm/compact_memory, and whether the original allocation request
can already succeed.  These don't apply to all callsites.

Move the checks out to the callers, so that later patches can deal with
them one by one.  No functional change intended.

[hannes@cmpxchg.org: fix comment, per Vlastimil]
Link: https://lkml.kernel.org/r/20230602144942.GC161817@cmpxchg.org
Link: https://lkml.kernel.org/r/20230519123959.77335-4-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
index 1f0328a2ba485cd1cc7a381fd24d9e5ec9810070..9f7cf3e1bf89d1a3934e9ed5ab1c3cd82c8a2d07 100644 (file)
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -90,7 +90,7 @@ extern enum compact_result try_to_compact_pages(gfp_t gfp_mask,
                struct page **page);
 extern void reset_isolation_suitable(pg_data_t *pgdat);
 extern enum compact_result compaction_suitable(struct zone *zone, int order,
-               unsigned int alloc_flags, int highest_zoneidx);
+                                              int highest_zoneidx);
 
 extern void compaction_defer_reset(struct zone *zone, int order,
                                bool alloc_success);
@@ -108,7 +108,7 @@ static inline void reset_isolation_suitable(pg_data_t *pgdat)
 }
 
 static inline enum compact_result compaction_suitable(struct zone *zone, int order,
-                                       int alloc_flags, int highest_zoneidx)
+                                                     int highest_zoneidx)
 {
        return COMPACT_SKIPPED;
 }

diff --git a/mm/compaction.c b/mm/compaction.c
index e23e00bec0301a615bdad38756cdf9b5f4fc2bdc..bb9b76244a5df10185c84d54454743ba8b8840a2 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2194,24 +2194,10 @@ static enum compact_result compact_finished(struct compact_control *cc)
 }
 
 static enum compact_result __compaction_suitable(struct zone *zone, int order,
-                                       unsigned int alloc_flags,
                                        int highest_zoneidx,
                                        unsigned long wmark_target)
 {
        unsigned long watermark;
-
-       if (is_via_compact_memory(order))
-               return COMPACT_CONTINUE;
-
-       watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
-       /*
-        * If watermarks for high-order allocation are already met, there
-        * should be no need for compaction at all.
-        */
-       if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
-                                                               alloc_flags))
-               return COMPACT_SUCCESS;
-
        /*
         * Watermarks for order-0 must be met for compaction to be able to
         * isolate free pages for migration targets. This means that the
@@ -2240,17 +2226,15 @@ static enum compact_result __compaction_suitable(struct zone *zone, int order,
  * compaction_suitable: Is this suitable to run compaction on this zone now?
  * Returns
  *   COMPACT_SKIPPED  - If there are too few free pages for compaction
- *   COMPACT_SUCCESS  - If the allocation would succeed without compaction
  *   COMPACT_CONTINUE - If compaction should run now
  */
 enum compact_result compaction_suitable(struct zone *zone, int order,
-                                       unsigned int alloc_flags,
                                        int highest_zoneidx)
 {
        enum compact_result ret;
        int fragindex;
 
-       ret = __compaction_suitable(zone, order, alloc_flags, highest_zoneidx,
+       ret = __compaction_suitable(zone, order, highest_zoneidx,
                                    zone_page_state(zone, NR_FREE_PAGES));
        /*
         * fragmentation index determines if allocation failures are due to
@@ -2294,7 +2278,16 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
        for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
                                ac->highest_zoneidx, ac->nodemask) {
                unsigned long available;
-               enum compact_result compact_result;
+               unsigned long watermark;
+
+               if (is_via_compact_memory(order))
+                       return true;
+
+               /* Allocation can already succeed, nothing to do */
+               watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
+               if (zone_watermark_ok(zone, order, watermark,
+                                     ac->highest_zoneidx, alloc_flags))
+                       continue;
 
                /*
                 * Do not consider all the reclaimable memory because we do not
@@ -2304,9 +2297,8 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
                 */
                available = zone_reclaimable_pages(zone) / order;
                available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
-               compact_result = __compaction_suitable(zone, order, alloc_flags,
-                               ac->highest_zoneidx, available);
-               if (compact_result == COMPACT_CONTINUE)
+               if (__compaction_suitable(zone, order, ac->highest_zoneidx,
+                                         available) == COMPACT_CONTINUE)
                        return true;
        }
 
@@ -2336,11 +2328,23 @@ compact_zone(struct compact_control *cc, struct capture_control *capc)
        INIT_LIST_HEAD(&cc->migratepages);
 
        cc->migratetype = gfp_migratetype(cc->gfp_mask);
-       ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
-                                                       cc->highest_zoneidx);
-       /* Compaction is likely to fail */
-       if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
-               return ret;
+
+       if (!is_via_compact_memory(cc->order)) {
+               unsigned long watermark;
+
+               /* Allocation can already succeed, nothing to do */
+               watermark = wmark_pages(cc->zone,
+                                       cc->alloc_flags & ALLOC_WMARK_MASK);
+               if (zone_watermark_ok(cc->zone, cc->order, watermark,
+                                     cc->highest_zoneidx, cc->alloc_flags))
+                       return COMPACT_SUCCESS;
+
+               ret = compaction_suitable(cc->zone, cc->order,
+                                         cc->highest_zoneidx);
+               /* Compaction is likely to fail */
+               if (ret == COMPACT_SKIPPED)
+                       return ret;
+       }
 
        /*
         * Clear pageblock skip if there were failures recently and compaction
@@ -2844,7 +2848,16 @@ static bool kcompactd_node_suitable(pg_data_t *pgdat)
                if (!populated_zone(zone))
                        continue;
 
-               if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
+               if (is_via_compact_memory(pgdat->kcompactd_max_order))
+                       return true;
+
+               /* Allocation can already succeed, check other zones */
+               if (zone_watermark_ok(zone, pgdat->kcompactd_max_order,
+                                     min_wmark_pages(zone),
+                                     highest_zoneidx, 0))
+                       continue;
+
+               if (compaction_suitable(zone, pgdat->kcompactd_max_order,
                                        highest_zoneidx) == COMPACT_CONTINUE)
                        return true;
        }
@@ -2882,10 +2895,18 @@ static void kcompactd_do_work(pg_data_t *pgdat)
                if (compaction_deferred(zone, cc.order))
                        continue;
 
-               if (compaction_suitable(zone, cc.order, 0, zoneid) !=
-                                                       COMPACT_CONTINUE)
+               if (is_via_compact_memory(cc.order))
+                       goto compact;
+
+               /* Allocation can already succeed, nothing to do */
+               if (zone_watermark_ok(zone, cc.order,
+                                     min_wmark_pages(zone), zoneid, 0))
                        continue;
 
+               if (compaction_suitable(zone, cc.order,
+                                       zoneid) != COMPACT_CONTINUE)
+                       continue;
+compact:
                if (kthread_should_stop())
                        return;
 

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 4637f6462e9c0520067fec1bdc33f5ff8ffe103a..9f8bfd1fcf58b76b6480e63e75fc3bce8c6b7d07 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -6399,14 +6399,17 @@ static inline bool should_continue_reclaim(struct pglist_data *pgdat,
                if (!managed_zone(zone))
                        continue;
 
-               switch (compaction_suitable(zone, sc->order, 0, sc->reclaim_idx)) {
-               case COMPACT_SUCCESS:
-               case COMPACT_CONTINUE:
+               if (sc->order == -1) /* is_via_compact_memory() */
+                       return false;
+
+               /* Allocation can already succeed, nothing to do */
+               if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
+                                     sc->reclaim_idx, 0))
+                       return false;
+
+               if (compaction_suitable(zone, sc->order,
+                                       sc->reclaim_idx) == COMPACT_CONTINUE)
                        return false;
-               default:
-                       /* check next zone */
-                       ;
-               }
        }
 
        /*
@@ -6594,16 +6597,20 @@ again:
 static inline bool compaction_ready(struct zone *zone, struct scan_control *sc)
 {
        unsigned long watermark;
-       enum compact_result suitable;
 
-       suitable = compaction_suitable(zone, sc->order, 0, sc->reclaim_idx);
-       if (suitable == COMPACT_SUCCESS)
-               /* Allocation should succeed already. Don't reclaim. */
+       if (sc->order == -1) /* is_via_compact_memory() */
+               goto suitable;
+
+       /* Allocation can already succeed, nothing to do */
+       if (zone_watermark_ok(zone, sc->order, min_wmark_pages(zone),
+                             sc->reclaim_idx, 0))
                return true;
-       if (suitable == COMPACT_SKIPPED)
-               /* Compaction cannot yet proceed. Do reclaim. */
-               return false;
 
+       /* Compaction cannot yet proceed. Do reclaim. */
+       if (compaction_suitable(zone, sc->order,
+                               sc->reclaim_idx) == COMPACT_SKIPPED)
+               return false;
+suitable:
        /*
         * Compaction is already possible, but it takes time to run and there
         * are potentially other callers using the pages just freed. So proceed