On 10/4/22 18:40, Paolo Valente wrote:
> When a bfq_queue Q is merged with another queue, several pieces of
> information are saved about Q. These pieces are stored in the
> bfq_io_cq data structure of the process associated with Q. In
> particular, each such piece is represented by a scalar field in
> bfq_io_cq.
>
> Yet, with a multi-actuator drive, a process gets associated with
> multiple bfq_queues: one queue for each of the N actuators. Each of
> these queues may undergo a merge. So, the bfq_io_cq data structure
> must be able to accommodate the above information for N queues.
>
> This commit solves this problem by turning each scalar field into an
> array of N elements (and by changing code so as to handle these
> arrays).
>
> This solution is written under the assumption that bfq_queues
> associated with different actuators cannot be cross-merged. This
> assumption holds naturally with basic queue merging: the latter is
> triggered by spatial locality, and sectors for different actuators are
> not close to each other. As for stable cross-merging, the assumption
> here is that it is disabled.
>
> Signed-off-by: Gabriele Felici <felicigb@xxxxxxxxx>
> Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
> ---
> block/bfq-iosched.c | 139 ++++++++++++++++++++++++--------------------
> block/bfq-iosched.h | 52 ++++++++++-------
> 2 files changed, 105 insertions(+), 86 deletions(-)
>
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 2a75009c1c06..dede0e948836 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -406,7 +406,7 @@ void bic_set_bfqq(struct bfq_io_cq *bic,
> */
> bic->bfqq[is_sync][actuator_idx] = bfqq;
>
> - if (bfqq && bic->stable_merge_bfqq == bfqq) {
> + if (bfqq && bic->stable_merge_bfqq[actuator_idx] == bfqq) {
> /*
> * Actually, these same instructions are executed also
> * in bfq_setup_cooperator, in case of abort or actual
> @@ -415,9 +415,9 @@ void bic_set_bfqq(struct bfq_io_cq *bic,
> * did so, we would nest even more complexity in this
> * function.
> */
> - bfq_put_stable_ref(bic->stable_merge_bfqq);
> + bfq_put_stable_ref(bic->stable_merge_bfqq[actuator_idx]);
>
> - bic->stable_merge_bfqq = NULL;
> + bic->stable_merge_bfqq[actuator_idx] = NULL;
> }
> }
>
> @@ -1176,36 +1176,38 @@ bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
> {
> unsigned int old_wr_coeff = 1;
> bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq);
> + unsigned int a_idx = bfqq->actuator_idx;
>
> - if (bic->saved_has_short_ttime)
> + if (bic->saved_has_short_ttime[a_idx])
> bfq_mark_bfqq_has_short_ttime(bfqq);
> else
> bfq_clear_bfqq_has_short_ttime(bfqq);
>
> - if (bic->saved_IO_bound)
> + if (bic->saved_IO_bound[a_idx])
> bfq_mark_bfqq_IO_bound(bfqq);
> else
> bfq_clear_bfqq_IO_bound(bfqq);
>
> - bfqq->last_serv_time_ns = bic->saved_last_serv_time_ns;
> - bfqq->inject_limit = bic->saved_inject_limit;
> - bfqq->decrease_time_jif = bic->saved_decrease_time_jif;
> + bfqq->last_serv_time_ns = bic->saved_last_serv_time_ns[a_idx];
> + bfqq->inject_limit = bic->saved_inject_limit[a_idx];
> + bfqq->decrease_time_jif = bic->saved_decrease_time_jif[a_idx];
>
> - bfqq->entity.new_weight = bic->saved_weight;
> - bfqq->ttime = bic->saved_ttime;
> - bfqq->io_start_time = bic->saved_io_start_time;
> - bfqq->tot_idle_time = bic->saved_tot_idle_time;
> + bfqq->entity.new_weight = bic->saved_weight[a_idx];
> + bfqq->ttime = bic->saved_ttime[a_idx];
> + bfqq->io_start_time = bic->saved_io_start_time[a_idx];
> + bfqq->tot_idle_time = bic->saved_tot_idle_time[a_idx];
> /*
> * Restore weight coefficient only if low_latency is on
> */
> if (bfqd->low_latency) {
> old_wr_coeff = bfqq->wr_coeff;
> - bfqq->wr_coeff = bic->saved_wr_coeff;
> + bfqq->wr_coeff = bic->saved_wr_coeff[a_idx];
> }
> - bfqq->service_from_wr = bic->saved_service_from_wr;
> - bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt;
> - bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish;
> - bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time;
> + bfqq->service_from_wr = bic->saved_service_from_wr[a_idx];
> + bfqq->wr_start_at_switch_to_srt =
> + bic->saved_wr_start_at_switch_to_srt[a_idx];
> + bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish[a_idx];
> + bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time[a_idx];
>
> if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) ||
> time_is_before_jiffies(bfqq->last_wr_start_finish +
> @@ -1824,6 +1826,16 @@ static bool bfq_bfqq_higher_class_or_weight(struct bfq_queue *bfqq,
> return bfqq_weight > in_serv_weight;
> }
>
> +/* 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.
> + */
> + return 0;
> +}
> +
> static bool bfq_better_to_idle(struct bfq_queue *bfqq);
>
> static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
> @@ -1878,7 +1890,9 @@ static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
> wr_or_deserves_wr = bfqd->low_latency &&
> (bfqq->wr_coeff > 1 ||
> (bfq_bfqq_sync(bfqq) &&
> - (bfqq->bic || RQ_BIC(rq)->stably_merged) &&
> + (bfqq->bic ||
> + RQ_BIC(rq)->stably_merged
> + [bfq_actuator_index(bfqd, rq->bio)]) &&
> (*interactive || soft_rt)));
>
> /*
> @@ -2466,16 +2480,6 @@ static void bfq_remove_request(struct request_queue *q,
>
> }
>
> -/* 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.
> - */
> - return 0;
> -}
> -
> static bool bfq_bio_merge(struct request_queue *q, struct bio *bio,
> unsigned int nr_segs)
> {
> @@ -2902,6 +2906,7 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> void *io_struct, bool request, struct bfq_io_cq *bic)
> {
> struct bfq_queue *in_service_bfqq, *new_bfqq;
> + unsigned int a_idx = bfqq->actuator_idx;
>
> /* if a merge has already been setup, then proceed with that first */
> if (bfqq->new_bfqq)
> @@ -2923,21 +2928,21 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> * stable merging) also if bic is associated with a
> * sync queue, but this bfqq is async
> */
> - if (bfq_bfqq_sync(bfqq) && bic->stable_merge_bfqq &&
> + if (bfq_bfqq_sync(bfqq) && bic->stable_merge_bfqq[a_idx] &&
> !bfq_bfqq_just_created(bfqq) &&
> time_is_before_jiffies(bfqq->split_time +
> msecs_to_jiffies(bfq_late_stable_merging)) &&
> time_is_before_jiffies(bfqq->creation_time +
> msecs_to_jiffies(bfq_late_stable_merging))) {
> struct bfq_queue *stable_merge_bfqq =
> - bic->stable_merge_bfqq;
> + bic->stable_merge_bfqq[a_idx];
> int proc_ref = min(bfqq_process_refs(bfqq),
> bfqq_process_refs(stable_merge_bfqq));
>
> /* deschedule stable merge, because done or aborted here */
> bfq_put_stable_ref(stable_merge_bfqq);
>
> - bic->stable_merge_bfqq = NULL;
> + bic->stable_merge_bfqq[a_idx] = NULL;
>
> if (!idling_boosts_thr_without_issues(bfqd, bfqq) &&
> proc_ref > 0) {
> @@ -2946,9 +2951,10 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> bfq_setup_merge(bfqq, stable_merge_bfqq);
>
> if (new_bfqq) {
> - bic->stably_merged = true;
> + bic->stably_merged[a_idx] = true;
> if (new_bfqq->bic)
> - new_bfqq->bic->stably_merged =
> + new_bfqq->bic->stably_merged
> + [new_bfqq->actuator_idx] =
> true;
> }
> return new_bfqq;
> @@ -3048,6 +3054,8 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
> {
> struct bfq_io_cq *bic = bfqq->bic;
> + /* State must be saved for the right queue index. */
> + unsigned int a_idx = bfqq->actuator_idx;
>
> /*
> * If !bfqq->bic, the queue is already shared or its requests
> @@ -3057,18 +3065,18 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
> if (!bic)
> return;
>
> - bic->saved_last_serv_time_ns = bfqq->last_serv_time_ns;
> - bic->saved_inject_limit = bfqq->inject_limit;
> - bic->saved_decrease_time_jif = bfqq->decrease_time_jif;
> -
> - bic->saved_weight = bfqq->entity.orig_weight;
> - bic->saved_ttime = bfqq->ttime;
> - bic->saved_has_short_ttime = bfq_bfqq_has_short_ttime(bfqq);
> - bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
> - bic->saved_io_start_time = bfqq->io_start_time;
> - bic->saved_tot_idle_time = bfqq->tot_idle_time;
> - bic->saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
> - bic->was_in_burst_list = !hlist_unhashed(&bfqq->burst_list_node);
> + bic->saved_last_serv_time_ns[a_idx] = bfqq->last_serv_time_ns;
> + bic->saved_inject_limit[a_idx] = bfqq->inject_limit;
> + bic->saved_decrease_time_jif[a_idx] = bfqq->decrease_time_jif;
> +
> + bic->saved_weight[a_idx] = bfqq->entity.orig_weight;
> + bic->saved_ttime[a_idx] = bfqq->ttime;
> + bic->saved_has_short_ttime[a_idx] = bfq_bfqq_has_short_ttime(bfqq);
> + bic->saved_IO_bound[a_idx] = bfq_bfqq_IO_bound(bfqq);
> + bic->saved_io_start_time[a_idx] = bfqq->io_start_time;
> + bic->saved_tot_idle_time[a_idx] = bfqq->tot_idle_time;
> + bic->saved_in_large_burst[a_idx] = bfq_bfqq_in_large_burst(bfqq);
> + bic->was_in_burst_list[a_idx] = !hlist_unhashed(&bfqq->burst_list_node);
> if (unlikely(bfq_bfqq_just_created(bfqq) &&
> !bfq_bfqq_in_large_burst(bfqq) &&
> bfqq->bfqd->low_latency)) {
> @@ -3081,17 +3089,17 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
> * to bfqq, so that to avoid that bfqq unjustly fails
> * to enjoy weight raising if split soon.
> */
> - bic->saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff;
> - bic->saved_wr_start_at_switch_to_srt = bfq_smallest_from_now();
> - bic->saved_wr_cur_max_time = bfq_wr_duration(bfqq->bfqd);
> - bic->saved_last_wr_start_finish = jiffies;
> + bic->saved_wr_coeff[a_idx] = bfqq->bfqd->bfq_wr_coeff;
> + bic->saved_wr_start_at_switch_to_srt[a_idx] = bfq_smallest_from_now();
> + bic->saved_wr_cur_max_time[a_idx] = bfq_wr_duration(bfqq->bfqd);
> + bic->saved_last_wr_start_finish[a_idx] = jiffies;
> } else {
> - bic->saved_wr_coeff = bfqq->wr_coeff;
> - bic->saved_wr_start_at_switch_to_srt =
> + bic->saved_wr_coeff[a_idx] = bfqq->wr_coeff;
> + bic->saved_wr_start_at_switch_to_srt[a_idx] =
> bfqq->wr_start_at_switch_to_srt;
> - bic->saved_service_from_wr = bfqq->service_from_wr;
> - bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish;
> - bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
> + bic->saved_service_from_wr[a_idx] = bfqq->service_from_wr;
> + bic->saved_last_wr_start_finish[a_idx] = bfqq->last_wr_start_finish;
> + bic->saved_wr_cur_max_time[a_idx] = bfqq->wr_cur_max_time;
> }
> }
>
> @@ -5423,8 +5431,8 @@ static void bfq_exit_icq(struct io_cq *icq)
> spin_lock_irqsave(&bfqd->lock, flags);
>
> for (act_idx = 0; act_idx < BFQ_NUM_ACTUATORS; act_idx++) {
> - if (bic->stable_merge_bfqq)
> - bfq_put_stable_ref(bic->stable_merge_bfqq);
> + if (bic->stable_merge_bfqq[act_idx])
> + bfq_put_stable_ref(bic->stable_merge_bfqq[act_idx]);
>
> bfq_exit_icq_bfqq(bic, true, act_idx);
> bfq_exit_icq_bfqq(bic, false, act_idx);
> @@ -5612,6 +5620,7 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> struct bfq_io_cq *bic,
> struct bfq_queue *last_bfqq_created)
> {
> + unsigned int a_idx = last_bfqq_created->actuator_idx;
> struct bfq_queue *new_bfqq =
> bfq_setup_merge(bfqq, last_bfqq_created);
>
> @@ -5619,8 +5628,8 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
> return bfqq;
>
> if (new_bfqq->bic)
> - new_bfqq->bic->stably_merged = true;
> - bic->stably_merged = true;
> + new_bfqq->bic->stably_merged[a_idx] = true;
> + bic->stably_merged[a_idx] = true;
>
> /*
> * Reusing merge functions. This implies that
> @@ -5750,7 +5759,8 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd,
> /*
> * Record the bfqq to merge to.
> */
> - bic->stable_merge_bfqq = last_bfqq_created;
> + bic->stable_merge_bfqq[last_bfqq_created->actuator_idx]
> + = last_bfqq_created;
> }
> }
>
> @@ -6684,12 +6694,12 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd,
>
> bic_set_bfqq(bic, bfqq, is_sync, act_idx);
> if (split && is_sync) {
> - if ((bic->was_in_burst_list && bfqd->large_burst) ||
> - bic->saved_in_large_burst)
> + if ((bic->was_in_burst_list[act_idx] && bfqd->large_burst) ||
> + bic->saved_in_large_burst[act_idx])
> bfq_mark_bfqq_in_large_burst(bfqq);
> else {
> bfq_clear_bfqq_in_large_burst(bfqq);
> - if (bic->was_in_burst_list)
> + if (bic->was_in_burst_list[act_idx])
> /*
> * If bfqq was in the current
> * burst list before being
> @@ -6778,6 +6788,7 @@ static struct bfq_queue *bfq_init_rq(struct request *rq)
> struct bfq_queue *bfqq;
> bool new_queue = false;
> bool bfqq_already_existing = false, split = false;
> + unsigned int a_idx = bfq_actuator_index(bfqd, bio);
>
> if (unlikely(!rq->elv.icq))
> return NULL;
> @@ -6804,12 +6815,12 @@ static struct bfq_queue *bfq_init_rq(struct request *rq)
> if (likely(!new_queue)) {
> /* If the queue was seeky for too long, break it apart. */
> if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq) &&
> - !bic->stably_merged) {
> + !bic->stably_merged[a_idx]) {
> struct bfq_queue *old_bfqq = bfqq;
>
> /* Update bic before losing reference to bfqq */
> if (bfq_bfqq_in_large_burst(bfqq))
> - bic->saved_in_large_burst = true;
> + bic->saved_in_large_burst[a_idx] = true;
>
> bfqq = bfq_split_bfqq(bic, bfqq);
> split = true;
> diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
> index 8b5225a9e080..0ff6be18f72a 100644
> --- a/block/bfq-iosched.h
> +++ b/block/bfq-iosched.h
> @@ -431,30 +431,37 @@ struct bfq_io_cq {
> uint64_t blkcg_serial_nr; /* the current blkcg serial */
> #endif
> /*
> - * Snapshot of the has_short_time flag before merging; taken
> - * to remember its value while the queue is merged, so as to
> - * be able to restore it in case of split.
> + * Several fields follow, which are used to support
> + * queue-merging operations. Each field is an array, because a
> + * process may be associated with multiple bfq_queues (see the
> + * field bfqq above). And each of these queues may undergo a
> + * merge.
> */
> - bool saved_has_short_ttime;
> + /*
> + * Snapshot of the has_short_time flags before merging; taken
> + * to remember their values while a queue is merged, so as to
> + * be able to restore them in case of split.
> + */
> + bool saved_has_short_ttime[BFQ_NUM_ACTUATORS];
> /*
> * Same purpose as the previous two fields for the I/O bound
> * classification of a queue.
> */
> - bool saved_IO_bound;
> + bool saved_IO_bound[BFQ_NUM_ACTUATORS];
>
> - u64 saved_io_start_time;
> - u64 saved_tot_idle_time;
> + u64 saved_io_start_time[BFQ_NUM_ACTUATORS];
> + u64 saved_tot_idle_time[BFQ_NUM_ACTUATORS];
>
> /*
> - * Same purpose as the previous fields for the value of the
> + * Same purpose as the previous fields for the values of the
> * field keeping the queue's belonging to a large burst
> */
> - bool saved_in_large_burst;
> + bool saved_in_large_burst[BFQ_NUM_ACTUATORS];
> /*
> * True if the queue belonged to a burst list before its merge
> * with another cooperating queue.
> */
> - bool was_in_burst_list;
> + bool was_in_burst_list[BFQ_NUM_ACTUATORS];
>
> /*
> * Save the weight when a merge occurs, to be able
> @@ -463,27 +470,28 @@ struct bfq_io_cq {
> * then the weight of the recycled queue could differ
> * from the weight of the original queue.
> */
> - unsigned int saved_weight;
> + unsigned int saved_weight[BFQ_NUM_ACTUATORS];
>
> /*
> * Similar to previous fields: save wr information.
> */
> - unsigned long saved_wr_coeff;
> - unsigned long saved_last_wr_start_finish;
> - unsigned long saved_service_from_wr;
> - unsigned long saved_wr_start_at_switch_to_srt;
> - unsigned int saved_wr_cur_max_time;
> - struct bfq_ttime saved_ttime;
> + unsigned long saved_wr_coeff[BFQ_NUM_ACTUATORS];
> + unsigned long saved_last_wr_start_finish[BFQ_NUM_ACTUATORS];
> + unsigned long saved_service_from_wr[BFQ_NUM_ACTUATORS];
> + unsigned long saved_wr_start_at_switch_to_srt[BFQ_NUM_ACTUATORS];
> + unsigned int saved_wr_cur_max_time[BFQ_NUM_ACTUATORS];
> + struct bfq_ttime saved_ttime[BFQ_NUM_ACTUATORS];
>
> /* Save also injection state */
> - u64 saved_last_serv_time_ns;
> - unsigned int saved_inject_limit;
> - unsigned long saved_decrease_time_jif;
> + u64 saved_last_serv_time_ns[BFQ_NUM_ACTUATORS];
> + unsigned int saved_inject_limit[BFQ_NUM_ACTUATORS];
> + unsigned long saved_decrease_time_jif[BFQ_NUM_ACTUATORS];
Instead of changing all these fields to an array, why not pack them into a
structure and have a single array of structures here ? That would be a lot
cleaner I think.
>
> /* candidate queue for a stable merge (due to close creation time) */
> - struct bfq_queue *stable_merge_bfqq;
> + struct bfq_queue *stable_merge_bfqq[BFQ_NUM_ACTUATORS];
> +
> + bool stably_merged[BFQ_NUM_ACTUATORS]; /* non splittable if true */
>
> - bool stably_merged; /* non splittable if true */
> unsigned int requests; /* Number of requests this process has in flight */
> };
>
--
Damien Le Moal
Western Digital Research
