map->swap_lock protects map->cleared from concurrent modification,
however sbitmap_deferred_clear() is already atomically drains it, so
it's guaranteed to not loose bits on concurrent
sbitmap_deferred_clear().
A one threaded tag heavy test on top of nullbk showed ~1.5% t-put
increase, and 3% -> 1% cycle reduction of sbitmap_get() according to perf.
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
* @cleared: word holding cleared bits
*/
unsigned long cleared ____cacheline_aligned_in_smp;
* @cleared: word holding cleared bits
*/
unsigned long cleared ____cacheline_aligned_in_smp;
-
- /**
- * @swap_lock: Held while swapping word <-> cleared
- */
- spinlock_t swap_lock;
} ____cacheline_aligned_in_smp;
/**
} ____cacheline_aligned_in_smp;
/**
static inline bool sbitmap_deferred_clear(struct sbitmap_word *map)
{
unsigned long mask, val;
static inline bool sbitmap_deferred_clear(struct sbitmap_word *map)
{
unsigned long mask, val;
- bool ret = false;
- unsigned long flags;
- spin_lock_irqsave(&map->swap_lock, flags);
-
- if (!map->cleared)
- goto out_unlock;
+ if (!READ_ONCE(map->cleared))
+ return false;
/*
* First get a stable cleared mask, setting the old mask to 0.
/*
* First get a stable cleared mask, setting the old mask to 0.
val = map->word;
} while (cmpxchg(&map->word, val, val & ~mask) != val);
val = map->word;
} while (cmpxchg(&map->word, val, val & ~mask) != val);
- ret = true;
-out_unlock:
- spin_unlock_irqrestore(&map->swap_lock, flags);
- return ret;
}
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
}
int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift,
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
for (i = 0; i < sb->map_nr; i++) {
sb->map[i].depth = min(depth, bits_per_word);
depth -= sb->map[i].depth;
- spin_lock_init(&sb->map[i].swap_lock);