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bfq-iosched: update shallow depth to smallest one used

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If our shallow depth is smaller than the wake batching of sbitmap,
we can introduce hangs. Ensure that sbitmap knows how low we'll go.

Acked-by: Paolo Valente <paolo.valente@linaro.org>
Reviewed-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2018-05-09 15:26:55 -06:00
parent a327553965
commit 483b7bf2e4
1 changed files with 14 additions and 3 deletions
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17
block/bfq-iosched.c
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@ -5081,10 +5081,13 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
/*
* See the comments on bfq_limit_depth for the purpose of
* the depths set in the function.
* the depths set in the function. Return minimum shallow depth we'll use.
*/
static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
static unsigned int bfq_update_depths(struct bfq_data *bfqd,
struct sbitmap_queue *bt)
{
unsigned int i, j, min_shallow = UINT_MAX;
/*
* In-word depths if no bfq_queue is being weight-raised:
* leaving 25% of tags only for sync reads.
@ -5115,14 +5118,22 @@ static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
bfqd->word_depths[1][0] = max(((1U << bt->sb.shift) * 3) >> 4, 1U);
/* no more than ~37% of tags for sync writes (~20% extra tags) */
bfqd->word_depths[1][1] = max(((1U << bt->sb.shift) * 6) >> 4, 1U);
for (i = 0; i < 2; i++)
for (j = 0; j < 2; j++)
min_shallow = min(min_shallow, bfqd->word_depths[i][j]);
return min_shallow;
}
static int bfq_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int index)
{
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
struct blk_mq_tags *tags = hctx->sched_tags;
unsigned int min_shallow;
bfq_update_depths(bfqd, &tags->bitmap_tags);
min_shallow = bfq_update_depths(bfqd, &tags->bitmap_tags);
sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, min_shallow);
return 0;
}