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author | Jens Axboe <axboe@fb.com> | 2017-01-28 01:08:31 +0300 |
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committer | Jens Axboe <axboe@fb.com> | 2017-01-28 01:08:31 +0300 |
commit | f924ba70c1b12706c6679d793202e8f4c125f7ae (patch) | |
tree | 978f8f56ccfa7c6fdb4be4ac6e498d73d44bf14f /lib | |
parent | 7a308bb3016f57e5be11a677d15b821536419d36 (diff) | |
parent | 400f73b23f457a82288814e21af57dbc9f3f2afd (diff) | |
download | linux-f924ba70c1b12706c6679d793202e8f4c125f7ae.tar.xz |
Merge branch 'for-4.11/block' into for-4.11/rq-refactor
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'lib')
-rw-r--r-- | lib/sbitmap.c | 139 |
1 files changed, 131 insertions, 8 deletions
diff --git a/lib/sbitmap.c b/lib/sbitmap.c index 2cecf05c82fd..55e11c4b2f3b 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -17,6 +17,7 @@ #include <linux/random.h> #include <linux/sbitmap.h> +#include <linux/seq_file.h> int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, gfp_t flags, int node) @@ -180,6 +181,62 @@ unsigned int sbitmap_weight(const struct sbitmap *sb) } EXPORT_SYMBOL_GPL(sbitmap_weight); +void sbitmap_show(struct sbitmap *sb, struct seq_file *m) +{ + seq_printf(m, "depth=%u\n", sb->depth); + seq_printf(m, "busy=%u\n", sbitmap_weight(sb)); + seq_printf(m, "bits_per_word=%u\n", 1U << sb->shift); + seq_printf(m, "map_nr=%u\n", sb->map_nr); +} +EXPORT_SYMBOL_GPL(sbitmap_show); + +static inline void emit_byte(struct seq_file *m, unsigned int offset, u8 byte) +{ + if ((offset & 0xf) == 0) { + if (offset != 0) + seq_putc(m, '\n'); + seq_printf(m, "%08x:", offset); + } + if ((offset & 0x1) == 0) + seq_putc(m, ' '); + seq_printf(m, "%02x", byte); +} + +void sbitmap_bitmap_show(struct sbitmap *sb, struct seq_file *m) +{ + u8 byte = 0; + unsigned int byte_bits = 0; + unsigned int offset = 0; + int i; + + for (i = 0; i < sb->map_nr; i++) { + unsigned long word = READ_ONCE(sb->map[i].word); + unsigned int word_bits = READ_ONCE(sb->map[i].depth); + + while (word_bits > 0) { + unsigned int bits = min(8 - byte_bits, word_bits); + + byte |= (word & (BIT(bits) - 1)) << byte_bits; + byte_bits += bits; + if (byte_bits == 8) { + emit_byte(m, offset, byte); + byte = 0; + byte_bits = 0; + offset++; + } + word >>= bits; + word_bits -= bits; + } + } + if (byte_bits) { + emit_byte(m, offset, byte); + offset++; + } + if (offset) + seq_putc(m, '\n'); +} +EXPORT_SYMBOL_GPL(sbitmap_bitmap_show); + static unsigned int sbq_calc_wake_batch(unsigned int depth) { unsigned int wake_batch; @@ -239,7 +296,19 @@ EXPORT_SYMBOL_GPL(sbitmap_queue_init_node); void sbitmap_queue_resize(struct sbitmap_queue *sbq, unsigned int depth) { - sbq->wake_batch = sbq_calc_wake_batch(depth); + unsigned int wake_batch = sbq_calc_wake_batch(depth); + int i; + + if (sbq->wake_batch != wake_batch) { + WRITE_ONCE(sbq->wake_batch, wake_batch); + /* + * Pairs with the memory barrier in sbq_wake_up() to ensure that + * the batch size is updated before the wait counts. + */ + smp_mb__before_atomic(); + for (i = 0; i < SBQ_WAIT_QUEUES; i++) + atomic_set(&sbq->ws[i].wait_cnt, 1); + } sbitmap_resize(&sbq->sb, depth); } EXPORT_SYMBOL_GPL(sbitmap_queue_resize); @@ -297,20 +366,39 @@ static struct sbq_wait_state *sbq_wake_ptr(struct sbitmap_queue *sbq) static void sbq_wake_up(struct sbitmap_queue *sbq) { struct sbq_wait_state *ws; + unsigned int wake_batch; int wait_cnt; - /* Ensure that the wait list checks occur after clear_bit(). */ - smp_mb(); + /* + * Pairs with the memory barrier in set_current_state() to ensure the + * proper ordering of clear_bit()/waitqueue_active() in the waker and + * test_and_set_bit()/prepare_to_wait()/finish_wait() in the waiter. See + * the comment on waitqueue_active(). This is __after_atomic because we + * just did clear_bit() in the caller. + */ + smp_mb__after_atomic(); ws = sbq_wake_ptr(sbq); if (!ws) return; wait_cnt = atomic_dec_return(&ws->wait_cnt); - if (unlikely(wait_cnt < 0)) - wait_cnt = atomic_inc_return(&ws->wait_cnt); - if (wait_cnt == 0) { - atomic_add(sbq->wake_batch, &ws->wait_cnt); + if (wait_cnt <= 0) { + wake_batch = READ_ONCE(sbq->wake_batch); + /* + * Pairs with the memory barrier in sbitmap_queue_resize() to + * ensure that we see the batch size update before the wait + * count is reset. + */ + smp_mb__before_atomic(); + /* + * If there are concurrent callers to sbq_wake_up(), the last + * one to decrement the wait count below zero will bump it back + * up. If there is a concurrent resize, the count reset will + * either cause the cmpxchg to fail or overwrite after the + * cmpxchg. + */ + atomic_cmpxchg(&ws->wait_cnt, wait_cnt, wait_cnt + wake_batch); sbq_index_atomic_inc(&sbq->wake_index); wake_up(&ws->wait); } @@ -331,7 +419,8 @@ void sbitmap_queue_wake_all(struct sbitmap_queue *sbq) int i, wake_index; /* - * Make sure all changes prior to this are visible from other CPUs. + * Pairs with the memory barrier in set_current_state() like in + * sbq_wake_up(). */ smp_mb(); wake_index = atomic_read(&sbq->wake_index); @@ -345,3 +434,37 @@ void sbitmap_queue_wake_all(struct sbitmap_queue *sbq) } } EXPORT_SYMBOL_GPL(sbitmap_queue_wake_all); + +void sbitmap_queue_show(struct sbitmap_queue *sbq, struct seq_file *m) +{ + bool first; + int i; + + sbitmap_show(&sbq->sb, m); + + seq_puts(m, "alloc_hint={"); + first = true; + for_each_possible_cpu(i) { + if (!first) + seq_puts(m, ", "); + first = false; + seq_printf(m, "%u", *per_cpu_ptr(sbq->alloc_hint, i)); + } + seq_puts(m, "}\n"); + + seq_printf(m, "wake_batch=%u\n", sbq->wake_batch); + seq_printf(m, "wake_index=%d\n", atomic_read(&sbq->wake_index)); + + seq_puts(m, "ws={\n"); + for (i = 0; i < SBQ_WAIT_QUEUES; i++) { + struct sbq_wait_state *ws = &sbq->ws[i]; + + seq_printf(m, "\t{.wait_cnt=%d, .wait=%s},\n", + atomic_read(&ws->wait_cnt), + waitqueue_active(&ws->wait) ? "active" : "inactive"); + } + seq_puts(m, "}\n"); + + seq_printf(m, "round_robin=%d\n", sbq->round_robin); +} +EXPORT_SYMBOL_GPL(sbitmap_queue_show); |