root/include/linux/compaction.h

DEFINITIONS

1. defer_compaction
2. compaction_deferred
3. compaction_defer_reset
4. compaction_restarting
5. try_to_compact_pages
6. compact_pgdat
7. reset_isolation_suitable
8. compaction_suitable
9. defer_compaction
10. compaction_deferred
11. compaction_register_node
12. compaction_unregister_node

#ifndef _LINUX_COMPACTION_H
#define _LINUX_COMPACTION_H

/* Return values for compact_zone() and try_to_compact_pages() */
/* compaction didn't start as it was deferred due to past failures */
#define COMPACT_DEFERRED        0
/* compaction didn't start as it was not possible or direct reclaim was more suitable */
#define COMPACT_SKIPPED         1
/* compaction should continue to another pageblock */
#define COMPACT_CONTINUE        2
/* direct compaction partially compacted a zone and there are suitable pages */
#define COMPACT_PARTIAL         3
/* The full zone was compacted */
#define COMPACT_COMPLETE        4

/* Used to signal whether compaction detected need_sched() or lock contention */
/* No contention detected */
#define COMPACT_CONTENDED_NONE  0
/* Either need_sched() was true or fatal signal pending */
#define COMPACT_CONTENDED_SCHED 1
/* Zone lock or lru_lock was contended in async compaction */
#define COMPACT_CONTENDED_LOCK  2

#ifdef CONFIG_COMPACTION
extern int sysctl_compact_memory;
extern int sysctl_compaction_handler(struct ctl_table *table, int write,
                        void __user *buffer, size_t *length, loff_t *ppos);
extern int sysctl_extfrag_threshold;
extern int sysctl_extfrag_handler(struct ctl_table *table, int write,
                        void __user *buffer, size_t *length, loff_t *ppos);

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,
                        enum migrate_mode mode, int *contended,
                        struct zone **candidate_zone);
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);

/* Do not skip compaction more than 64 times */
#define COMPACT_MAX_DEFER_SHIFT 6

/*
 * Compaction is deferred when compaction fails to result in a page
 * allocation success. 1 << compact_defer_limit compactions are skipped up
 * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT
 */
static inline void defer_compaction(struct zone *zone, int order)
{
        zone->compact_considered = 0;
        zone->compact_defer_shift++;

        if (order < zone->compact_order_failed)
                zone->compact_order_failed = order;

        if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT)
                zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT;
}

/* Returns true if compaction should be skipped this time */
static inline bool compaction_deferred(struct zone *zone, int order)
{
        unsigned long defer_limit = 1UL << zone->compact_defer_shift;

        if (order < zone->compact_order_failed)
                return false;

        /* Avoid possible overflow */
        if (++zone->compact_considered > defer_limit)
                zone->compact_considered = defer_limit;

        return zone->compact_considered < defer_limit;
}

/*
 * Update defer tracking counters after successful compaction of given order,
 * which means an allocation either succeeded (alloc_success == true) or is
 * expected to succeed.
 */
static inline void compaction_defer_reset(struct zone *zone, int order,
                bool alloc_success)
{
        if (alloc_success) {
                zone->compact_considered = 0;
                zone->compact_defer_shift = 0;
        }
        if (order >= zone->compact_order_failed)
                zone->compact_order_failed = order + 1;
}

/* Returns true if restarting compaction after many failures */
static inline bool compaction_restarting(struct zone *zone, int order)
{
        if (order < zone->compact_order_failed)
                return false;

        return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT &&
                zone->compact_considered >= 1UL << zone->compact_defer_shift;
}

#else
static inline unsigned long try_to_compact_pages(struct zonelist *zonelist,
                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
                        enum migrate_mode mode, int *contended,
                        struct zone **candidate_zone)
{
        return COMPACT_CONTINUE;
}

static inline void compact_pgdat(pg_data_t *pgdat, int order)
{
}

static inline void reset_isolation_suitable(pg_data_t *pgdat)
{
}

static inline unsigned long compaction_suitable(struct zone *zone, int order)
{
        return COMPACT_SKIPPED;
}

static inline void defer_compaction(struct zone *zone, int order)
{
}

static inline bool compaction_deferred(struct zone *zone, int order)
{
        return true;
}

#endif /* CONFIG_COMPACTION */

#if defined(CONFIG_COMPACTION) && defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
extern int compaction_register_node(struct node *node);
extern void compaction_unregister_node(struct node *node);

#else

static inline int compaction_register_node(struct node *node)
{
        return 0;
}

static inline void compaction_unregister_node(struct node *node)
{
}
#endif /* CONFIG_COMPACTION && CONFIG_SYSFS && CONFIG_NUMA */

#endif /* _LINUX_COMPACTION_H */