On 05/07/2014 04:22 AM, David Rientjes wrote:
We're going to want to manipulate the migration mode for compaction in the page
allocator, and currently compact_control's sync field is only a bool.

Currently, we only do MIGRATE_ASYNC or MIGRATE_SYNC_LIGHT compaction depending
on the value of this bool.  Convert the bool to enum migrate_mode and pass the
migration mode in directly.  Later, we'll want to avoid MIGRATE_SYNC_LIGHT for
thp allocations in the pagefault patch to avoid unnecessary latency.

This also alters compaction triggered from sysfs, either for the entire system
or for a node, to force MIGRATE_SYNC.

Suggested-by: Mel Gorman <mgor...@suse.de>
Signed-off-by: David Rientjes <rient...@google.com>
---
  include/linux/compaction.h |  4 ++--
  mm/compaction.c            | 36 +++++++++++++++++++-----------------
  mm/internal.h              |  2 +-
  mm/page_alloc.c            | 37 ++++++++++++++++---------------------
  4 files changed, 38 insertions(+), 41 deletions(-)

diff --git a/include/linux/compaction.h b/include/linux/compaction.h
--- a/include/linux/compaction.h
+++ b/include/linux/compaction.h
@@ -22,7 +22,7 @@ extern int sysctl_extfrag_handler(struct ctl_table *table, 
int write,
  extern int fragmentation_index(struct zone *zone, unsigned int order);
  extern unsigned long try_to_compact_pages(struct zonelist *zonelist,
                        int order, gfp_t gfp_mask, nodemask_t *mask,
-                       bool sync, bool *contended);
+                       enum migrate_mode sync, bool *contended);

Everywhere else it's 'mode' and only in this function it's still called 'sync', that's confusing.
Afterwards:

Acked-by: Vlastimil Babka <vba...@suse.cz>

  extern void compact_pgdat(pg_data_t *pgdat, int order);
  extern void reset_isolation_suitable(pg_data_t *pgdat);
  extern unsigned long compaction_suitable(struct zone *zone, int order);
@@ -91,7 +91,7 @@ static inline bool compaction_restarting(struct zone *zone, 
int order)
  #else
  static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
-                       bool sync, bool *contended)
+                       enum migrate_mode sync, bool *contended)
  {
        return COMPACT_CONTINUE;
  }
diff --git a/mm/compaction.c b/mm/compaction.c
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -161,7 +161,8 @@ static void update_pageblock_skip(struct compact_control 
*cc,
                        return;
                if (pfn > zone->compact_cached_migrate_pfn[0])
                        zone->compact_cached_migrate_pfn[0] = pfn;
-               if (cc->sync && pfn > zone->compact_cached_migrate_pfn[1])
+               if (cc->mode != MIGRATE_ASYNC &&
+                   pfn > zone->compact_cached_migrate_pfn[1])
                        zone->compact_cached_migrate_pfn[1] = pfn;
        } else {
                if (cc->finished_update_free)
@@ -208,7 +209,7 @@ static bool compact_checklock_irqsave(spinlock_t *lock, 
unsigned long *flags,
                }

                /* async aborts if taking too long or contended */
-               if (!cc->sync) {
+               if (cc->mode == MIGRATE_ASYNC) {
                        cc->contended = true;
                        return false;
                }
@@ -479,7 +480,8 @@ isolate_migratepages_range(struct zone *zone, struct 
compact_control *cc,
        bool locked = false;
        struct page *page = NULL, *valid_page = NULL;
        bool set_unsuitable = true;
-       const isolate_mode_t mode = (!cc->sync ? ISOLATE_ASYNC_MIGRATE : 0) |
+       const isolate_mode_t mode = (cc->mode == MIGRATE_ASYNC ?
+                                       ISOLATE_ASYNC_MIGRATE : 0) |
                                    (unevictable ? ISOLATE_UNEVICTABLE : 0);

        /*
@@ -489,7 +491,7 @@ isolate_migratepages_range(struct zone *zone, struct 
compact_control *cc,
         */
        while (unlikely(too_many_isolated(zone))) {
                /* async migration should just abort */
-               if (!cc->sync)
+               if (cc->mode == MIGRATE_ASYNC)
                        return 0;

                congestion_wait(BLK_RW_ASYNC, HZ/10);
@@ -554,7 +556,8 @@ isolate_migratepages_range(struct zone *zone, struct 
compact_control *cc,
                         * the minimum amount of work satisfies the allocation
                         */
                        mt = get_pageblock_migratetype(page);
-                       if (!cc->sync && !migrate_async_suitable(mt)) {
+                       if (cc->mode == MIGRATE_ASYNC &&
+                           !migrate_async_suitable(mt)) {
                                set_unsuitable = false;
                                goto next_pageblock;
                        }
@@ -990,6 +993,7 @@ static int compact_zone(struct zone *zone, struct 
compact_control *cc)
        int ret;
        unsigned long start_pfn = zone->zone_start_pfn;
        unsigned long end_pfn = zone_end_pfn(zone);
+       const bool sync = cc->mode != MIGRATE_ASYNC;

        ret = compaction_suitable(zone, cc->order);
        switch (ret) {
@@ -1015,7 +1019,7 @@ static int compact_zone(struct zone *zone, struct 
compact_control *cc)
         * information on where the scanners should start but check that it
         * is initialised by ensuring the values are within zone boundaries.
         */
-       cc->migrate_pfn = zone->compact_cached_migrate_pfn[cc->sync];
+       cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync];
        cc->free_pfn = zone->compact_cached_free_pfn;
        if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) {
                cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1);
@@ -1049,8 +1053,7 @@ static int compact_zone(struct zone *zone, struct 
compact_control *cc)

                nr_migrate = cc->nr_migratepages;
                err = migrate_pages(&cc->migratepages, compaction_alloc,
-                               compaction_free, (unsigned long)cc,
-                               cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC,
+                               compaction_free, (unsigned long)cc, cc->mode,
                                MR_COMPACTION);
                update_nr_listpages(cc);
                nr_remaining = cc->nr_migratepages;
@@ -1083,9 +1086,8 @@ out:
        return ret;
  }

-static unsigned long compact_zone_order(struct zone *zone,
-                                int order, gfp_t gfp_mask,
-                                bool sync, bool *contended)
+static unsigned long compact_zone_order(struct zone *zone, int order,
+               gfp_t gfp_mask, enum migrate_mode mode, bool *contended)
  {
        unsigned long ret;
        struct compact_control cc = {
@@ -1094,7 +1096,7 @@ static unsigned long compact_zone_order(struct zone *zone,
                .order = order,
                .migratetype = allocflags_to_migratetype(gfp_mask),
                .zone = zone,
-               .sync = sync,
+               .mode = mode,
        };
        INIT_LIST_HEAD(&cc.freepages);
        INIT_LIST_HEAD(&cc.migratepages);
@@ -1116,7 +1118,7 @@ int sysctl_extfrag_threshold = 500;
   * @order: The order of the current allocation
   * @gfp_mask: The GFP mask of the current allocation
   * @nodemask: The allowed nodes to allocate from
- * @sync: Whether migration is synchronous or not
+ * @sync: The migration mode for async, sync light, or sync migration
   * @contended: Return value that is true if compaction was aborted due to 
lock contention
   * @page: Optionally capture a free page of the requested order during 
compaction
   *
@@ -1124,7 +1126,7 @@ int sysctl_extfrag_threshold = 500;
   */
  unsigned long try_to_compact_pages(struct zonelist *zonelist,
                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
-                       bool sync, bool *contended)
+                       enum migrate_mode sync, bool *contended)
  {
        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
        int may_enter_fs = gfp_mask & __GFP_FS;
@@ -1189,7 +1191,7 @@ static void __compact_pgdat(pg_data_t *pgdat, struct 
compact_control *cc)
                                                low_wmark_pages(zone), 0, 0))
                                compaction_defer_reset(zone, cc->order, false);
                        /* Currently async compaction is never deferred. */
-                       else if (cc->sync)
+                       else if (cc->mode != MIGRATE_ASYNC)
                                defer_compaction(zone, cc->order);
                }

@@ -1202,7 +1204,7 @@ void compact_pgdat(pg_data_t *pgdat, int order)
  {
        struct compact_control cc = {
                .order = order,
-               .sync = false,
+               .mode = MIGRATE_ASYNC,
        };

        if (!order)
@@ -1215,7 +1217,7 @@ static void compact_node(int nid)
  {
        struct compact_control cc = {
                .order = -1,
-               .sync = true,
+               .mode = MIGRATE_SYNC,
                .ignore_skip_hint = true,
        };

diff --git a/mm/internal.h b/mm/internal.h
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -134,7 +134,7 @@ struct compact_control {
        unsigned long nr_migratepages;  /* Number of pages to migrate */
        unsigned long free_pfn;         /* isolate_freepages search base */
        unsigned long migrate_pfn;      /* isolate_migratepages search base */
-       bool sync;                      /* Synchronous migration */
+       enum migrate_mode mode;         /* Async or sync migration mode */
        bool ignore_skip_hint;          /* Scan blocks even if marked skip */
        bool finished_update_free;      /* True when the zone cached pfns are
                                         * no longer being updated
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2226,7 +2226,7 @@ static struct page *
  __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
-       int migratetype, bool sync_migration,
+       int migratetype, enum migrate_mode mode,
        bool *contended_compaction, bool *deferred_compaction,
        unsigned long *did_some_progress)
  {
@@ -2240,7 +2240,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int 
order,

        current->flags |= PF_MEMALLOC;
        *did_some_progress = try_to_compact_pages(zonelist, order, gfp_mask,
-                                               nodemask, sync_migration,
+                                               nodemask, mode,
                                                contended_compaction);
        current->flags &= ~PF_MEMALLOC;

@@ -2273,7 +2273,7 @@ __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int 
order,
                 * As async compaction considers a subset of pageblocks, only
                 * defer if the failure was a sync compaction failure.
                 */
-               if (sync_migration)
+               if (mode != MIGRATE_ASYNC)
                        defer_compaction(preferred_zone, order);

                cond_resched();
@@ -2286,9 +2286,8 @@ static inline struct page *
  __alloc_pages_direct_compact(gfp_t gfp_mask, unsigned int order,
        struct zonelist *zonelist, enum zone_type high_zoneidx,
        nodemask_t *nodemask, int alloc_flags, struct zone *preferred_zone,
-       int migratetype, bool sync_migration,
-       bool *contended_compaction, bool *deferred_compaction,
-       unsigned long *did_some_progress)
+       int migratetype, enum migrate_mode mode, bool *contended_compaction,
+       bool *deferred_compaction, unsigned long *did_some_progress)
  {
        return NULL;
  }
@@ -2483,7 +2482,7 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order,
        int alloc_flags;
        unsigned long pages_reclaimed = 0;
        unsigned long did_some_progress;
-       bool sync_migration = false;
+       enum migrate_mode migration_mode = MIGRATE_ASYNC;
        bool deferred_compaction = false;
        bool contended_compaction = false;

@@ -2577,17 +2576,15 @@ rebalance:
         * Try direct compaction. The first pass is asynchronous. Subsequent
         * attempts after direct reclaim are synchronous
         */
-       page = __alloc_pages_direct_compact(gfp_mask, order,
-                                       zonelist, high_zoneidx,
-                                       nodemask,
-                                       alloc_flags, preferred_zone,
-                                       migratetype, sync_migration,
-                                       &contended_compaction,
+       page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
+                                       high_zoneidx, nodemask, alloc_flags,
+                                       preferred_zone, migratetype,
+                                       migration_mode, &contended_compaction,
                                        &deferred_compaction,
                                        &did_some_progress);
        if (page)
                goto got_pg;
-       sync_migration = true;
+       migration_mode = MIGRATE_SYNC_LIGHT;

        /*
         * If compaction is deferred for high-order allocations, it is because
@@ -2662,12 +2659,10 @@ rebalance:
                 * direct reclaim and reclaim/compaction depends on compaction
                 * being called after reclaim so call directly if necessary
                 */
-               page = __alloc_pages_direct_compact(gfp_mask, order,
-                                       zonelist, high_zoneidx,
-                                       nodemask,
-                                       alloc_flags, preferred_zone,
-                                       migratetype, sync_migration,
-                                       &contended_compaction,
+               page = __alloc_pages_direct_compact(gfp_mask, order, zonelist,
+                                       high_zoneidx, nodemask, alloc_flags,
+                                       preferred_zone, migratetype,
+                                       migration_mode, &contended_compaction,
                                        &deferred_compaction,
                                        &did_some_progress);
                if (page)
@@ -6254,7 +6249,7 @@ int alloc_contig_range(unsigned long start, unsigned long 
end,
                .nr_migratepages = 0,
                .order = -1,
                .zone = page_zone(pfn_to_page(start)),
-               .sync = true,
+               .sync = MIGRATE_SYNC_LIGHT,
                .ignore_skip_hint = true,
        };
        INIT_LIST_HEAD(&cc.migratepages);


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