mm: remove reclaim and compaction retry approximations

If per-zone LRU accounting is available then there is no point
approximating whether reclaim and compaction should retry based on pgdat
statistics.  This is effectively a revert of "mm, vmstat: remove zone
and node double accounting by approximating retries" with the difference
that inactive/active stats are still available.  This preserves the
history of why the approximation was retried and why it had to be
reverted to handle OOM kills on 32-bit systems.

Link: http://lkml.kernel.org/r/1469110261-7365-4-git-send-email-mgorman@techsingularity.net
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index 1a813ad..ca0fbc4 100644 (file)
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -116,6 +116,7 @@ enum zone_stat_item {
        NR_ZONE_INACTIVE_FILE,
        NR_ZONE_ACTIVE_FILE,
        NR_ZONE_UNEVICTABLE,
+       NR_ZONE_WRITE_PENDING,  /* Count of dirty, writeback and unstable pages */
        NR_MLOCK,               /* mlock()ed pages found and moved off LRU */
        NR_SLAB_RECLAIMABLE,
        NR_SLAB_UNRECLAIMABLE,

diff --git a/include/linux/swap.h b/include/linux/swap.h
index cc753c6..b17cc48 100644 (file)
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -307,6 +307,7 @@ extern void lru_cache_add_active_or_unevictable(struct page *page,
                                                struct vm_area_struct *vma);
 
 /* linux/mm/vmscan.c */
+extern unsigned long zone_reclaimable_pages(struct zone *zone);
 extern unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat);
 extern unsigned long try_to_free_pages(struct zonelist *zonelist, int order,
                                        gfp_t gfp_mask, nodemask_t *mask);

diff --git a/mm/compaction.c b/mm/compaction.c
index cd93ea2..e5995f3 100644 (file)
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -1438,11 +1438,6 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
 {
        struct zone *zone;
        struct zoneref *z;
-       pg_data_t *last_pgdat = NULL;
-
-       /* Do not retry compaction for zone-constrained allocations */
-       if (ac->high_zoneidx < ZONE_NORMAL)
-               return false;
 
        /*
         * Make sure at least one zone would pass __compaction_suitable if we continue
@@ -1453,27 +1448,14 @@ bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
                unsigned long available;
                enum compact_result compact_result;
 
-               if (last_pgdat == zone->zone_pgdat)
-                       continue;
-
-               /*
-                * This over-estimates the number of pages available for
-                * reclaim/compaction but walking the LRU would take too
-                * long. The consequences are that compaction may retry
-                * longer than it should for a zone-constrained allocation
-                * request.
-                */
-               last_pgdat = zone->zone_pgdat;
-               available = pgdat_reclaimable_pages(zone->zone_pgdat) / order;
-
                /*
                 * Do not consider all the reclaimable memory because we do not
                 * want to trash just for a single high order allocation which
                 * is even not guaranteed to appear even if __compaction_suitable
                 * is happy about the watermark check.
                 */
+               available = zone_reclaimable_pages(zone) / order;
                available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
-               available = min(zone->managed_pages, available);
                compact_result = __compaction_suitable(zone, order, alloc_flags,
                                ac_classzone_idx(ac), available);
                if (compact_result != COMPACT_SKIPPED &&

diff --git a/mm/migrate.c b/mm/migrate.c
index ed2f85e..ed02682 100644 (file)
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -513,7 +513,9 @@ int migrate_page_move_mapping(struct address_space *mapping,
                }
                if (dirty && mapping_cap_account_dirty(mapping)) {
                        __dec_node_state(oldzone->zone_pgdat, NR_FILE_DIRTY);
+                       __dec_zone_state(oldzone, NR_ZONE_WRITE_PENDING);
                        __inc_node_state(newzone->zone_pgdat, NR_FILE_DIRTY);
+                       __inc_zone_state(newzone, NR_ZONE_WRITE_PENDING);
                }
        }
        local_irq_enable();

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 7b5920a..f4cd7d8 100644 (file)
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2462,6 +2462,7 @@ void account_page_dirtied(struct page *page, struct address_space *mapping)
 
                mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_DIRTY);
                __inc_node_page_state(page, NR_FILE_DIRTY);
+               __inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
                __inc_node_page_state(page, NR_DIRTIED);
                __inc_wb_stat(wb, WB_RECLAIMABLE);
                __inc_wb_stat(wb, WB_DIRTIED);
@@ -2483,6 +2484,7 @@ void account_page_cleaned(struct page *page, struct address_space *mapping,
        if (mapping_cap_account_dirty(mapping)) {
                mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY);
                dec_node_page_state(page, NR_FILE_DIRTY);
+               dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
                dec_wb_stat(wb, WB_RECLAIMABLE);
                task_io_account_cancelled_write(PAGE_SIZE);
        }
@@ -2739,6 +2741,7 @@ int clear_page_dirty_for_io(struct page *page)
                if (TestClearPageDirty(page)) {
                        mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_DIRTY);
                        dec_node_page_state(page, NR_FILE_DIRTY);
+                       dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
                        dec_wb_stat(wb, WB_RECLAIMABLE);
                        ret = 1;
                }
@@ -2785,6 +2788,7 @@ int test_clear_page_writeback(struct page *page)
        if (ret) {
                mem_cgroup_dec_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
                dec_node_page_state(page, NR_WRITEBACK);
+               dec_zone_page_state(page, NR_ZONE_WRITE_PENDING);
                inc_node_page_state(page, NR_WRITTEN);
        }
        unlock_page_memcg(page);
@@ -2839,6 +2843,7 @@ int __test_set_page_writeback(struct page *page, bool keep_write)
        if (!ret) {
                mem_cgroup_inc_page_stat(page, MEM_CGROUP_STAT_WRITEBACK);
                inc_node_page_state(page, NR_WRITEBACK);
+               inc_zone_page_state(page, NR_ZONE_WRITE_PENDING);
        }
        unlock_page_memcg(page);
        return ret;

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 759cfa8..dfdb608 100644 (file)
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3402,7 +3402,6 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
 {
        struct zone *zone;
        struct zoneref *z;
-       pg_data_t *current_pgdat = NULL;
 
        /*
         * Make sure we converge to OOM if we cannot make any progress
@@ -3412,15 +3411,6 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                return false;
 
        /*
-        * Blindly retry lowmem allocation requests that are often ignored by
-        * the OOM killer up to MAX_RECLAIM_RETRIES as we not have a reliable
-        * and fast means of calculating reclaimable, dirty and writeback pages
-        * in eligible zones.
-        */
-       if (ac->high_zoneidx < ZONE_NORMAL)
-               goto out;
-
-       /*
         * Keep reclaiming pages while there is a chance this will lead
         * somewhere.  If none of the target zones can satisfy our allocation
         * request even if all reclaimable pages are considered then we are
@@ -3430,38 +3420,18 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                                        ac->nodemask) {
                unsigned long available;
                unsigned long reclaimable;
-               int zid;
 
-               if (current_pgdat == zone->zone_pgdat)
-                       continue;
-
-               current_pgdat = zone->zone_pgdat;
-               available = reclaimable = pgdat_reclaimable_pages(current_pgdat);
+               available = reclaimable = zone_reclaimable_pages(zone);
                available -= DIV_ROUND_UP(no_progress_loops * available,
                                          MAX_RECLAIM_RETRIES);
-
-               /* Account for all free pages on eligible zones */
-               for (zid = 0; zid <= zone_idx(zone); zid++) {
-                       struct zone *acct_zone = &current_pgdat->node_zones[zid];
-
-                       available += zone_page_state_snapshot(acct_zone, NR_FREE_PAGES);
-               }
+               available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
 
                /*
                 * Would the allocation succeed if we reclaimed the whole
-                * available? This is approximate because there is no
-                * accurate count of reclaimable pages per zone.
+                * available?
                 */
-               for (zid = 0; zid <= zone_idx(zone); zid++) {
-                       struct zone *check_zone = &current_pgdat->node_zones[zid];
-                       unsigned long estimate;
-
-                       estimate = min(check_zone->managed_pages, available);
-                       if (!__zone_watermark_ok(check_zone, order,
-                                       min_wmark_pages(check_zone), ac_classzone_idx(ac),
-                                       alloc_flags, estimate))
-                               continue;
-
+               if (__zone_watermark_ok(zone, order, min_wmark_pages(zone),
+                               ac_classzone_idx(ac), alloc_flags, available)) {
                        /*
                         * If we didn't make any progress and have a lot of
                         * dirty + writeback pages then we should wait for
@@ -3471,16 +3441,15 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order,
                        if (!did_some_progress) {
                                unsigned long write_pending;
 
-                               write_pending =
-                                       node_page_state(current_pgdat, NR_WRITEBACK) +
-                                       node_page_state(current_pgdat, NR_FILE_DIRTY);
+                               write_pending = zone_page_state_snapshot(zone,
+                                                       NR_ZONE_WRITE_PENDING);
 
                                if (2 * write_pending > reclaimable) {
                                        congestion_wait(BLK_RW_ASYNC, HZ/10);
                                        return true;
                                }
                        }
-out:
+
                        /*
                         * Memory allocation/reclaim might be called from a WQ
                         * context and the current implementation of the WQ
@@ -4361,6 +4330,7 @@ void show_free_areas(unsigned int filter)
                        " active_file:%lukB"
                        " inactive_file:%lukB"
                        " unevictable:%lukB"
+                       " writepending:%lukB"
                        " present:%lukB"
                        " managed:%lukB"
                        " mlocked:%lukB"
@@ -4383,6 +4353,7 @@ void show_free_areas(unsigned int filter)
                        K(zone_page_state(zone, NR_ZONE_ACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_INACTIVE_FILE)),
                        K(zone_page_state(zone, NR_ZONE_UNEVICTABLE)),
+                       K(zone_page_state(zone, NR_ZONE_WRITE_PENDING)),
                        K(zone->present_pages),
                        K(zone->managed_pages),
                        K(zone_page_state(zone, NR_MLOCK)),

diff --git a/mm/vmscan.c b/mm/vmscan.c
index 222d540..134381a 100644 (file)
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -194,6 +194,24 @@ static bool sane_reclaim(struct scan_control *sc)
 }
 #endif
 
+/*
+ * This misses isolated pages which are not accounted for to save counters.
+ * As the data only determines if reclaim or compaction continues, it is
+ * not expected that isolated pages will be a dominating factor.
+ */
+unsigned long zone_reclaimable_pages(struct zone *zone)
+{
+       unsigned long nr;
+
+       nr = zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_FILE) +
+               zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_FILE);
+       if (get_nr_swap_pages() > 0)
+               nr += zone_page_state_snapshot(zone, NR_ZONE_INACTIVE_ANON) +
+                       zone_page_state_snapshot(zone, NR_ZONE_ACTIVE_ANON);
+
+       return nr;
+}
+
 unsigned long pgdat_reclaimable_pages(struct pglist_data *pgdat)
 {
        unsigned long nr;

diff --git a/mm/vmstat.c b/mm/vmstat.c
index 053075a..89cec42 100644 (file)
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -926,6 +926,7 @@ const char * const vmstat_text[] = {
        "nr_zone_inactive_file",
        "nr_zone_active_file",
        "nr_zone_unevictable",
+       "nr_zone_write_pending",
        "nr_mlock",
        "nr_slab_reclaimable",
        "nr_slab_unreclaimable",