On 11/4/22 01:26, Paolo Valente wrote:
> From: Federico Gavioli <f.gavioli97@xxxxxxxxx>
>
> This patch implements the code to gather the content of the
> independent_access_ranges structure from the request_queue and copy
> it into the queue's bfq_data. This copy is done at queue initialization.
>
> We copy the access ranges into the bfq_data to avoid taking the queue
> lock each time we access the ranges.
>
> This implementation, however, puts a limit to the maximum independent
> ranges supported by the scheduler. Such a limit is equal to the constant
> BFQ_MAX_ACTUATORS. This limit was placed to avoid the allocation of
> dynamic memory.
>
> Co-developed-by: Rory Chen <rory.c.chen@xxxxxxxxxxx>
> Signed-off-by: Rory Chen <rory.c.chen@xxxxxxxxxxx>
> Signed-off-by: Federico Gavioli <f.gavioli97@xxxxxxxxx>
> Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
> ---
> block/bfq-iosched.c | 54 ++++++++++++++++++++++++++++++++++++++-------
> block/bfq-iosched.h | 5 +++++
> 2 files changed, 51 insertions(+), 8 deletions(-)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index c94b80e3f685..106c8820cc5c 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -1831,10 +1831,26 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq,
> /* get the index of the actuator that will serve bio */
> static unsigned int bfq_actuator_index(struct bfq_data *bfqd, struct bio *bio)
> {
> - /*
> - * Multi-actuator support not complete yet, so always return 0
> - * for the moment.
> - */
> + struct blk_independent_access_range *iar;
> + unsigned int i;
> + sector_t end;
> +
> + /* no search needed if one or zero ranges present */
> + if (bfqd->num_actuators < 2)
> + return 0;
> +
> + /* bio_end_sector(bio) gives the sector after the last one */
> + end = bio_end_sector(bio) - 1;
> +
> + for (i = 0; i < bfqd->num_actuators; i++) {
> + iar = &(bfqd->ia_ranges[i]);
> + if (end >= iar->sector && end < iar->sector + iar->nr_sectors)
> + return i;
> + }
> +
> + WARN_ONCE(true,
> + "bfq_actuator_index: bio sector out of ranges: end=%llu\n",
> + end);
> return 0;
> }
>
> @@ -2479,7 +2495,6 @@ static void bfq_remove_request(struct request_queue *q,
>
> if (rq->cmd_flags & REQ_META)
> bfqq->meta_pending--;
> -
whiteline change
> }
>
> static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
> @@ -7144,6 +7159,8 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
> {
> struct bfq_data *bfqd;
> struct elevator_queue *eq;
> + unsigned int i;
> + struct blk_independent_access_ranges *ia_ranges = q->disk->ia_ranges;
>
> eq = elevator_alloc(q, e);
> if (!eq)
> @@ -7187,10 +7204,31 @@ static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
> bfqd->queue = q;
>
> /*
> - * Multi-actuator support not complete yet, default to single
> - * actuator for the moment.
> + * If the disk supports multiple actuators, we copy the independent
> + * access ranges from the request queue structure.
> */
> - bfqd->num_actuators = 1;
> + spin_lock_irq(&q->queue_lock);
> + if (ia_ranges) {
> + /*
> + * Check if the disk ia_ranges size exceeds the current bfq
> + * actuator limit.
> + */
> + if (ia_ranges->nr_ia_ranges > BFQ_MAX_ACTUATORS) {
> + pr_crit("nr_ia_ranges higher than act limit: iars=%d, max=%d.\n",
> + ia_ranges->nr_ia_ranges, BFQ_MAX_ACTUATORS);
> + pr_crit("Falling back to single actuator mode.\n");
> + bfqd->num_actuators = 0;
> + } else {
> + bfqd->num_actuators = ia_ranges->nr_ia_ranges;
> +
> + for (i = 0; i < bfqd->num_actuators; i++)
> + bfqd->ia_ranges[i] = ia_ranges->ia_range[i];
> + }
> + } else {
> + bfqd->num_actuators = 0;
That is very weird. The default should be 1 actuator.
ia_ranges->nr_ia_ranges is 0 when the disk does not provide any range
information, meaning it is a regular disk with a single actuator.
> + }
> +
> + spin_unlock_irq(&q->queue_lock);
>
> INIT_LIST_HEAD(&bfqd->dispatch);
>
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index f1c2e77cbf9a..90130a893c8f 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -811,6 +811,11 @@ struct bfq_data {
> */
> unsigned int num_actuators;
>
> + /*
> + * Disk independent access ranges for each actuator
> + * in this device.
> + */
> + struct blk_independent_access_range ia_ranges[BFQ_MAX_ACTUATORS];
I fail to see how keeping this information is useful, especially given
that this struct contains a kobj. Why not just copy the sector &
nr_sectors fields into struct bfq_queue ? That would also work for the
single actuator case as then sector will be 0 and nr_sectors will be the
disk total capacity.
I think this patch should be first in the series. That will avoid having
the empty bfq_actuator_index() function.
> };
>
> enum bfqq_state_flags {
--
Damien Le Moal
Western Digital Research
