On Thu, May 10, 2018 at 10:24:21AM -0600, Jens Axboe wrote:
> It doesn't change, so don't put it in the per-IO hot path.
>
> Acked-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
Reviewed-by: Omar Sandoval <osandov@xxxxxx>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> ---
> block/bfq-iosched.c | 97 +++++++++++++++++++++++++++--------------------------
> 1 file changed, 50 insertions(+), 47 deletions(-)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index db38e88a5670..0cd8aa80c32d 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -487,46 +487,6 @@ static struct request *bfq_choose_req(struct bfq_data *bfqd,
> }
>
> /*
> - * See the comments on bfq_limit_depth for the purpose of
> - * the depths set in the function.
> - */
> -static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
> -{
> - bfqd->sb_shift = bt->sb.shift;
> -
> - /*
> - * In-word depths if no bfq_queue is being weight-raised:
> - * leaving 25% of tags only for sync reads.
> - *
> - * In next formulas, right-shift the value
> - * (1U<<bfqd->sb_shift), instead of computing directly
> - * (1U<<(bfqd->sb_shift - something)), to be robust against
> - * any possible value of bfqd->sb_shift, without having to
> - * limit 'something'.
> - */
> - /* no more than 50% of tags for async I/O */
> - bfqd->word_depths[0][0] = max((1U<<bfqd->sb_shift)>>1, 1U);
> - /*
> - * no more than 75% of tags for sync writes (25% extra tags
> - * w.r.t. async I/O, to prevent async I/O from starving sync
> - * writes)
> - */
> - bfqd->word_depths[0][1] = max(((1U<<bfqd->sb_shift) * 3)>>2, 1U);
> -
> - /*
> - * In-word depths in case some bfq_queue is being weight-
> - * raised: leaving ~63% of tags for sync reads. This is the
> - * highest percentage for which, in our tests, application
> - * start-up times didn't suffer from any regression due to tag
> - * shortage.
> - */
> - /* no more than ~18% of tags for async I/O */
> - bfqd->word_depths[1][0] = max(((1U<<bfqd->sb_shift) * 3)>>4, 1U);
> - /* no more than ~37% of tags for sync writes (~20% extra tags) */
> - bfqd->word_depths[1][1] = max(((1U<<bfqd->sb_shift) * 6)>>4, 1U);
> -}
> -
> -/*
> * Async I/O can easily starve sync I/O (both sync reads and sync
> * writes), by consuming all tags. Similarly, storms of sync writes,
> * such as those that sync(2) may trigger, can starve sync reads.
> @@ -535,18 +495,11 @@ static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
> */
> static void bfq_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
> {
> - struct blk_mq_tags *tags = blk_mq_tags_from_data(data);
> struct bfq_data *bfqd = data->q->elevator->elevator_data;
> - struct sbitmap_queue *bt;
>
> if (op_is_sync(op) && !op_is_write(op))
> return;
>
> - bt = &tags->bitmap_tags;
> -
> - if (unlikely(bfqd->sb_shift != bt->sb.shift))
> - bfq_update_depths(bfqd, bt);
> -
> data->shallow_depth =
> bfqd->word_depths[!!bfqd->wr_busy_queues][op_is_sync(op)];
>
> @@ -5126,6 +5079,55 @@ void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
> __bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
> }
>
> +/*
> + * See the comments on bfq_limit_depth for the purpose of
> + * the depths set in the function.
> + */
> +static void bfq_update_depths(struct bfq_data *bfqd, struct sbitmap_queue *bt)
> +{
> + bfqd->sb_shift = bt->sb.shift;
> +
> + /*
> + * In-word depths if no bfq_queue is being weight-raised:
> + * leaving 25% of tags only for sync reads.
> + *
> + * In next formulas, right-shift the value
> + * (1U<<bfqd->sb_shift), instead of computing directly
> + * (1U<<(bfqd->sb_shift - something)), to be robust against
> + * any possible value of bfqd->sb_shift, without having to
> + * limit 'something'.
> + */
> + /* no more than 50% of tags for async I/O */
> + bfqd->word_depths[0][0] = max((1U<<bfqd->sb_shift)>>1, 1U);
> + /*
> + * no more than 75% of tags for sync writes (25% extra tags
> + * w.r.t. async I/O, to prevent async I/O from starving sync
> + * writes)
> + */
> + bfqd->word_depths[0][1] = max(((1U<<bfqd->sb_shift) * 3)>>2, 1U);
> +
> + /*
> + * In-word depths in case some bfq_queue is being weight-
> + * raised: leaving ~63% of tags for sync reads. This is the
> + * highest percentage for which, in our tests, application
> + * start-up times didn't suffer from any regression due to tag
> + * shortage.
> + */
> + /* no more than ~18% of tags for async I/O */
> + bfqd->word_depths[1][0] = max(((1U<<bfqd->sb_shift) * 3)>>4, 1U);
> + /* no more than ~37% of tags for sync writes (~20% extra tags) */
> + bfqd->word_depths[1][1] = max(((1U<<bfqd->sb_shift) * 6)>>4, 1U);
> +}
> +
> +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;
> +
> + bfq_update_depths(bfqd, &tags->bitmap_tags);
> + return 0;
> +}
> +
> static void bfq_exit_queue(struct elevator_queue *e)
> {
> struct bfq_data *bfqd = e->elevator_data;
> @@ -5547,6 +5549,7 @@ static struct elevator_type iosched_bfq_mq = {
> .requests_merged = bfq_requests_merged,
> .request_merged = bfq_request_merged,
> .has_work = bfq_has_work,
> + .init_hctx = bfq_init_hctx,
> .init_sched = bfq_init_queue,
> .exit_sched = bfq_exit_queue,
> },
> --
> 2.7.4
>
