Commit 483b7bf2 authored by Jens Axboe's avatar Jens Axboe
Browse files

bfq-iosched: update shallow depth to smallest one used 



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: default avatarPaolo Valente <paolo.valente@linaro.org>
Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent a3275539

block/bfq-iosched.c

+14 −3
Original line number Diff line number Diff line
@@ -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;

}