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 <[email protected]>
Reviewed-by: Omar Sandoval <[email protected]> > Signed-off-by: Jens Axboe <[email protected]> > --- > 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 >
