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| author | Chong Yuan <chong.yuan@memblaze.com> | 2015-04-15 11:39:29 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2015-04-15 11:39:29 -0600 |
| commit | 889fa31f00b218a2cef96c32a6b3f57e6d3bf918 (patch) | |
| tree | 12338bd403f6fd84d8e2b98624aceaa3a4b9998b /block/blk-mq.c | |
| parent | dc48e56d761610da4ea1088d1bea0a030b8e3e43 (diff) | |
| download | lwn-889fa31f00b218a2cef96c32a6b3f57e6d3bf918.tar.gz lwn-889fa31f00b218a2cef96c32a6b3f57e6d3bf918.zip | |
blk-mq: reduce unnecessary software queue looping
In flush_busy_ctxs() and blk_mq_hctx_has_pending(), regardless of how many
ctxs assigned to one hctx, they will all loop hctx->ctx_map.map_size
times. Here hctx->ctx_map.map_size is a const ALIGN(nr_cpu_ids, 8) / 8.
Especially, flush_busy_ctxs() is in hot code path. And it's unnecessary.
Change ->map_size to contain the actually mapped software queues, so we
only loop for as many iterations as we have to.
And remove cpumask setting and nr_ctx count in blk_mq_init_cpu_queues()
since they are all re-done in blk_mq_map_swqueue().
blk_mq_map_swqueue().
Signed-off-by: Chong Yuan <chong.yuan@memblaze.com>
Reviewed-by: Wenbo Wang <wenbo.wang@memblaze.com>
Updated by me for formatting and commenting.
Signed-off-by: Jens Axboe <axboe@fb.com>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 13 |
1 files changed, 9 insertions, 4 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 1192f85e5ff3..0b49e42e5310 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1522,8 +1522,6 @@ static int blk_mq_alloc_bitmap(struct blk_mq_ctxmap *bitmap, int node) if (!bitmap->map) return -ENOMEM; - bitmap->map_size = num_maps; - total = nr_cpu_ids; for (i = 0; i < num_maps; i++) { bitmap->map[i].depth = min(total, bitmap->bits_per_word); @@ -1764,8 +1762,6 @@ static void blk_mq_init_cpu_queues(struct request_queue *q, continue; hctx = q->mq_ops->map_queue(q, i); - cpumask_set_cpu(i, hctx->cpumask); - hctx->nr_ctx++; /* * Set local node, IFF we have more than one hw queue. If @@ -1802,6 +1798,8 @@ static void blk_mq_map_swqueue(struct request_queue *q) } queue_for_each_hw_ctx(q, hctx, i) { + struct blk_mq_ctxmap *map = &hctx->ctx_map; + /* * If no software queues are mapped to this hardware queue, * disable it and free the request entries. @@ -1818,6 +1816,13 @@ static void blk_mq_map_swqueue(struct request_queue *q) } /* + * Set the map size to the number of mapped software queues. + * This is more accurate and more efficient than looping + * over all possibly mapped software queues. + */ + map->map_size = hctx->nr_ctx / map->bits_per_word; + + /* * Initialize batch roundrobin counts */ hctx->next_cpu = cpumask_first(hctx->cpumask); |