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| author | Omar Sandoval <osandov@fb.com> | 2016-09-17 01:28:25 -0700 |
|---|---|---|
| committer | Jens Axboe <axboe@fb.com> | 2016-09-17 08:39:14 -0600 |
| commit | 98d95416dbfaf4910caadfb4ddc75e4aacbdff8c (patch) | |
| tree | ed6a08e6d4358da522265ac1e6a595fe8db35572 | |
| parent | f4a644db86669d938c71f19560aebf69d4720d63 (diff) | |
| download | linux-98d95416dbfaf4910caadfb4ddc75e4aacbdff8c.tar.gz linux-98d95416dbfaf4910caadfb4ddc75e4aacbdff8c.tar.bz2 linux-98d95416dbfaf4910caadfb4ddc75e4aacbdff8c.zip | |
sbitmap: randomize initial alloc_hint values
In order to get good cache behavior from a sbitmap, we want each CPU to
stick to its own cacheline(s) as much as possible. This might happen
naturally as the bitmap gets filled up and the alloc_hint values spread
out, but we really want this behavior from the start. blk-mq apparently
intended to do this, but the code to do this was never wired up. Get rid
of the dead code and make it part of the sbitmap library.
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
| -rw-r--r-- | block/blk-mq-tag.c | 8 | ||||
| -rw-r--r-- | block/blk-mq-tag.h | 1 | ||||
| -rw-r--r-- | lib/sbitmap.c | 6 |
3 files changed, 6 insertions, 9 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index e1c2bedb0bf9..cef618f6fc92 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -7,7 +7,6 @@ */ #include <linux/kernel.h> #include <linux/module.h> -#include <linux/random.h> #include <linux/blk-mq.h> #include "blk.h" @@ -419,13 +418,6 @@ void blk_mq_free_tags(struct blk_mq_tags *tags) kfree(tags); } -void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *tag) -{ - unsigned int depth = tags->nr_tags - tags->nr_reserved_tags; - - *tag = prandom_u32() % depth; -} - int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int tdepth) { tdepth -= tags->nr_reserved_tags; diff --git a/block/blk-mq-tag.h b/block/blk-mq-tag.h index f90b850ce43d..09f4cc0aaa84 100644 --- a/block/blk-mq-tag.h +++ b/block/blk-mq-tag.h @@ -30,7 +30,6 @@ extern void blk_mq_put_tag(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx, unsigned int tag); extern bool blk_mq_has_free_tags(struct blk_mq_tags *tags); extern ssize_t blk_mq_tag_sysfs_show(struct blk_mq_tags *tags, char *page); -extern void blk_mq_tag_init_last_tag(struct blk_mq_tags *tags, unsigned int *last_tag); extern int blk_mq_tag_update_depth(struct blk_mq_tags *tags, unsigned int depth); extern void blk_mq_tag_wakeup_all(struct blk_mq_tags *tags, bool); void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, diff --git a/lib/sbitmap.c b/lib/sbitmap.c index be55f744b771..928b82a733f2 100644 --- a/lib/sbitmap.c +++ b/lib/sbitmap.c @@ -15,6 +15,7 @@ * along with this program. If not, see <https://www.gnu.org/licenses/>. */ +#include <linux/random.h> #include <linux/sbitmap.h> int sbitmap_init_node(struct sbitmap *sb, unsigned int depth, int shift, @@ -211,6 +212,11 @@ int sbitmap_queue_init_node(struct sbitmap_queue *sbq, unsigned int depth, return -ENOMEM; } + if (depth && !round_robin) { + for_each_possible_cpu(i) + *per_cpu_ptr(sbq->alloc_hint, i) = prandom_u32() % depth; + } + sbq->wake_batch = sbq_calc_wake_batch(depth); atomic_set(&sbq->wake_index, 0); |