[PATCH V5 4/8] block, bfq: turn bfqq_data into an array in bfq_io_cq

From: Paolo Valente
Date: Sun Oct 30 2022 - 06:04:04 EST

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When a bfq_queue Q is merged with another queue, several pieces of
information are saved about Q. These pieces are stored in the
bfqq_data field in the bfq_io_cq data structure of the process
associated with Q.

Yet, with a multi-actuator drive, a process may get 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 the bfqq_data scalar field
into an array of N elements (and by changing code so as to handle
this array).

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: Gianmarco Lusvardi <glusvardi@xxxxxxxxxx>
Signed-off-by: Giulio Barabino <giuliobarabino99@xxxxxxxxx>
Signed-off-by: Emiliano Maccaferri <inbox@xxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Paolo Valente <paolo.valente@xxxxxxxxxx>
---
block/bfq-iosched.c | 170 ++++++++++++++++++++++++--------------------
block/bfq-iosched.h | 12 ++--
2 files changed, 101 insertions(+), 81 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 139b8f1ba439..bfdf954da5b7 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -404,10 +404,10 @@ void bic_set_bfqq(struct bfq_io_cq *bic,
* we cancel the stable merge if
* bic->stable_merge_bfqq == bfqq.
*/
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[actuator_idx];
bic->bfqq[is_sync][actuator_idx] = bfqq;

- if (bfqq && bfqq_data.stable_merge_bfqq == bfqq) {
+ if (bfqq && bfqq_data->stable_merge_bfqq == bfqq) {
/*
* Actually, these same instructions are executed also
* in bfq_setup_cooperator, in case of abort or actual
@@ -416,9 +416,9 @@ void bic_set_bfqq(struct bfq_io_cq *bic,
* did so, we would nest even more complexity in this
* function.
*/
- bfq_put_stable_ref(bfqq_data.stable_merge_bfqq);
+ bfq_put_stable_ref(bfqq_data->stable_merge_bfqq);

- bfqq_data.stable_merge_bfqq = NULL;
+ bfqq_data->stable_merge_bfqq = NULL;
}
}

@@ -1175,40 +1175,43 @@ static void
bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_data *bfqd,
struct bfq_io_cq *bic, bool bfq_already_existing)
{
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
unsigned int old_wr_coeff = 1;
bool busy = bfq_already_existing && bfq_bfqq_busy(bfqq);
+ unsigned int a_idx = bfqq->actuator_idx;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[a_idx];

- if (bfqq_data.saved_has_short_ttime)
+ if (bfqq_data->saved_has_short_ttime)
bfq_mark_bfqq_has_short_ttime(bfqq);
else
bfq_clear_bfqq_has_short_ttime(bfqq);

- if (bfqq_data.saved_IO_bound)
+ if (bfqq_data->saved_IO_bound)
bfq_mark_bfqq_IO_bound(bfqq);
else
bfq_clear_bfqq_IO_bound(bfqq);

- bfqq->last_serv_time_ns = bfqq_data.saved_last_serv_time_ns;
- bfqq->inject_limit = bfqq_data.saved_inject_limit;
- bfqq->decrease_time_jif = bfqq_data.saved_decrease_time_jif;
-
- bfqq->entity.new_weight = bfqq_data.saved_weight;
- bfqq->ttime = bfqq_data.saved_ttime;
- bfqq->io_start_time = bfqq_data.saved_io_start_time;
- bfqq->tot_idle_time = bfqq_data.saved_tot_idle_time;
+ bfqq->last_serv_time_ns =
+ bfqq_data->saved_last_serv_time_ns;
+ bfqq->inject_limit = bfqq_data->saved_inject_limit;
+ bfqq->decrease_time_jif =
+ bfqq_data->saved_decrease_time_jif;
+ bfqq->entity.new_weight = bfqq_data->saved_weight;
+ bfqq->ttime = bfqq_data->saved_ttime;
+ bfqq->io_start_time = bfqq_data->saved_io_start_time;
+ bfqq->tot_idle_time = bfqq_data->saved_tot_idle_time;
/*
* Restore weight coefficient only if low_latency is on
*/
if (bfqd->low_latency) {
old_wr_coeff = bfqq->wr_coeff;
- bfqq->wr_coeff = bfqq_data.saved_wr_coeff;
+ bfqq->wr_coeff = bfqq_data->saved_wr_coeff;
}
- bfqq->service_from_wr = bfqq_data.saved_service_from_wr;
+ bfqq->service_from_wr = bfqq_data->saved_service_from_wr;
bfqq->wr_start_at_switch_to_srt =
- bfqq_data.saved_wr_start_at_switch_to_srt;
- bfqq->last_wr_start_finish = bfqq_data.saved_last_wr_start_finish;
- bfqq->wr_cur_max_time = bfqq_data.saved_wr_cur_max_time;
+ bfqq_data->saved_wr_start_at_switch_to_srt;
+ bfqq->last_wr_start_finish =
+ bfqq_data->saved_last_wr_start_finish;
+ bfqq->wr_cur_max_time = bfqq_data->saved_wr_cur_max_time;

if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) ||
time_is_before_jiffies(bfqq->last_wr_start_finish +
@@ -1827,6 +1830,16 @@ 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,
@@ -1881,7 +1894,9 @@ 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)->bfqq_data.stably_merged) &&
+ (bfqq->bic ||
+ RQ_BIC(rq)->bfqq_data[bfq_actuator_index(bfqd, rq->bio)]
+ .stably_merged) &&
(*interactive || soft_rt)));

/*
@@ -2469,16 +2484,6 @@ 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)
{
@@ -2905,7 +2910,8 @@ 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;
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
+ unsigned int a_idx = bfqq->actuator_idx;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[a_idx];

/* if a merge has already been setup, then proceed with that first */
if (bfqq->new_bfqq)
@@ -2927,21 +2933,22 @@ 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) && bfqq_data.stable_merge_bfqq &&
+ if (bfq_bfqq_sync(bfqq) &&
+ bfqq_data->stable_merge_bfqq &&
!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 =
- bfqq_data.stable_merge_bfqq;
+ bfqq_data->stable_merge_bfqq;
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);

- bfqq_data.stable_merge_bfqq = NULL;
+ bfqq_data->stable_merge_bfqq = NULL;

if (!idling_boosts_thr_without_issues(bfqd, bfqq) &&
proc_ref > 0) {
@@ -2950,10 +2957,11 @@ bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
bfq_setup_merge(bfqq, stable_merge_bfqq);

if (new_bfqq) {
- bfqq_data.stably_merged = true;
+ bfqq_data->stably_merged = true;
if (new_bfqq->bic)
- new_bfqq->bic->bfqq_data.stably_merged =
- true;
+ new_bfqq->bic->bfqq_data
+ [new_bfqq->actuator_idx]
+ .stably_merged = true;
}
return new_bfqq;
} else
@@ -3052,7 +3060,9 @@ 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;
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
+ /* State must be saved for the right queue index. */
+ unsigned int a_idx = bfqq->actuator_idx;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[a_idx];

/*
* If !bfqq->bic, the queue is already shared or its requests
@@ -3062,19 +3072,23 @@ static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
if (!bic)
return;

- bfqq_data.saved_last_serv_time_ns = bfqq->last_serv_time_ns;
- bfqq_data.saved_inject_limit = bfqq->inject_limit;
- bfqq_data.saved_decrease_time_jif = bfqq->decrease_time_jif;
+ bfqq_data->saved_last_serv_time_ns =
+ bfqq->last_serv_time_ns;
+ bfqq_data->saved_inject_limit =
+ bfqq->inject_limit;
+ bfqq_data->saved_decrease_time_jif =
+ bfqq->decrease_time_jif;

- bfqq_data.saved_weight = bfqq->entity.orig_weight;
- bfqq_data.saved_ttime = bfqq->ttime;
- bfqq_data.saved_has_short_ttime =
+ bfqq_data->saved_weight = bfqq->entity.orig_weight;
+ bfqq_data->saved_ttime = bfqq->ttime;
+ bfqq_data->saved_has_short_ttime =
bfq_bfqq_has_short_ttime(bfqq);
- bfqq_data.saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
- bfqq_data.saved_io_start_time = bfqq->io_start_time;
- bfqq_data.saved_tot_idle_time = bfqq->tot_idle_time;
- bfqq_data.saved_in_large_burst = bfq_bfqq_in_large_burst(bfqq);
- bfqq_data.was_in_burst_list =
+ bfqq_data->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
+ bfqq_data->saved_io_start_time = bfqq->io_start_time;
+ bfqq_data->saved_tot_idle_time = bfqq->tot_idle_time;
+ bfqq_data->saved_in_large_burst =
+ bfq_bfqq_in_large_burst(bfqq);
+ bfqq_data->was_in_burst_list =
!hlist_unhashed(&bfqq->burst_list_node);

if (unlikely(bfq_bfqq_just_created(bfqq) &&
@@ -3089,21 +3103,23 @@ 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.
*/
- bfqq_data.saved_wr_coeff = bfqq->bfqd->bfq_wr_coeff;
- bfqq_data.saved_wr_start_at_switch_to_srt =
+ bfqq_data->saved_wr_coeff =
+ bfqq->bfqd->bfq_wr_coeff;
+ bfqq_data->saved_wr_start_at_switch_to_srt =
bfq_smallest_from_now();
- bfqq_data.saved_wr_cur_max_time =
+ bfqq_data->saved_wr_cur_max_time =
bfq_wr_duration(bfqq->bfqd);
- bfqq_data.saved_last_wr_start_finish = jiffies;
+ bfqq_data->saved_last_wr_start_finish = jiffies;
} else {
- bfqq_data.saved_wr_coeff = bfqq->wr_coeff;
- bfqq_data.saved_wr_start_at_switch_to_srt =
+ bfqq_data->saved_wr_coeff = bfqq->wr_coeff;
+ bfqq_data->saved_wr_start_at_switch_to_srt =
bfqq->wr_start_at_switch_to_srt;
- bfqq_data.saved_service_from_wr =
+ bfqq_data->saved_service_from_wr =
bfqq->service_from_wr;
- bfqq_data.saved_last_wr_start_finish =
+ bfqq_data->saved_last_wr_start_finish =
bfqq->last_wr_start_finish;
- bfqq_data.saved_wr_cur_max_time = bfqq->wr_cur_max_time;
+ bfqq_data->saved_wr_cur_max_time =
+ bfqq->wr_cur_max_time;
}
}

@@ -5425,7 +5441,7 @@ static void bfq_exit_icq(struct io_cq *icq)
unsigned long flags;
unsigned int act_idx;
unsigned int num_actuators;
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
+ struct bfq_iocq_bfqq_data *bfqq_data = bic->bfqq_data;

/*
* bfqd is NULL if scheduler already exited, and in that case
@@ -5445,10 +5461,10 @@ static void bfq_exit_icq(struct io_cq *icq)
num_actuators = BFQ_MAX_ACTUATORS;
}

- if (bfqq_data.stable_merge_bfqq)
- bfq_put_stable_ref(bfqq_data.stable_merge_bfqq);
-
for (act_idx = 0; act_idx < num_actuators; act_idx++) {
+ if (bfqq_data[act_idx].stable_merge_bfqq)
+ bfq_put_stable_ref(bfqq_data[act_idx].stable_merge_bfqq);
+
bfq_exit_icq_bfqq(bic, true, act_idx);
bfq_exit_icq_bfqq(bic, false, act_idx);
}
@@ -5635,16 +5651,16 @@ 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);
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;

if (!new_bfqq)
return bfqq;

if (new_bfqq->bic)
- new_bfqq->bic->bfqq_data.stably_merged = true;
- bfqq_data.stably_merged = true;
+ new_bfqq->bic->bfqq_data[a_idx].stably_merged = true;
+ bic->bfqq_data[a_idx].stably_merged = true;

/*
* Reusing merge functions. This implies that
@@ -5713,7 +5729,6 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd,
&bfqd->last_bfqq_created;

struct bfq_queue *last_bfqq_created = *source_bfqq;
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;

/*
* If last_bfqq_created has not been set yet, then init it. If
@@ -5775,7 +5790,8 @@ static struct bfq_queue *bfq_do_or_sched_stable_merge(struct bfq_data *bfqd,
/*
* Record the bfqq to merge to.
*/
- bfqq_data.stable_merge_bfqq = last_bfqq_created;
+ bic->bfqq_data[last_bfqq_created->actuator_idx].stable_merge_bfqq =
+ last_bfqq_created;
}
}

@@ -6696,7 +6712,7 @@ static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd,
{
unsigned int act_idx = bfq_actuator_index(bfqd, bio);
struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync, act_idx);
- struct bfq_iocq_bfqq_data bfqq_data = bic->bfqq_data;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data[act_idx];

if (likely(bfqq && bfqq != &bfqd->oom_bfqq))
return bfqq;
@@ -6710,12 +6726,13 @@ 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 ((bfqq_data.was_in_burst_list && bfqd->large_burst) ||
- bfqq_data.saved_in_large_burst)
+ if ((bfqq_data->was_in_burst_list &&
+ bfqd->large_burst) ||
+ bfqq_data->saved_in_large_burst)
bfq_mark_bfqq_in_large_burst(bfqq);
else {
bfq_clear_bfqq_in_large_burst(bfqq);
- if (bfqq_data.was_in_burst_list)
+ if (bfqq_data->was_in_burst_list)
/*
* If bfqq was in the current
* burst list before being
@@ -6804,7 +6821,7 @@ 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;
- struct bfq_iocq_bfqq_data bfqq_data;
+ unsigned int a_idx = bfq_actuator_index(bfqd, bio);

if (unlikely(!rq->elv.icq))
return NULL;
@@ -6828,17 +6845,16 @@ static struct bfq_queue *bfq_init_rq(struct request *rq)
bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync,
&new_queue);

- bfqq_data = bic->bfqq_data;
-
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) &&
- !bfqq_data.stably_merged) {
+ !bic->bfqq_data[a_idx].stably_merged) {
struct bfq_queue *old_bfqq = bfqq;

/* Update bic before losing reference to bfqq */
if (bfq_bfqq_in_large_burst(bfqq))
- bfqq_data.saved_in_large_burst = true;
+ bic->bfqq_data[a_idx].saved_in_large_burst =
+ true;

bfqq = bfq_split_bfqq(bic, bfqq);
split = true;
diff --git a/block/bfq-iosched.h b/block/bfq-iosched.h
index f2e8ab91951c..e27897d66a0f 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -416,7 +416,7 @@ struct bfq_queue {
struct bfq_iocq_bfqq_data {
/*
* Snapshot of the has_short_time flag before merging; taken
- * to remember its value while the queue is merged, so as to
+ * to remember its values while the queue is merged, so as to
* be able to restore it in case of split.
*/
bool saved_has_short_ttime;
@@ -430,7 +430,7 @@ struct bfq_iocq_bfqq_data {
u64 saved_tot_idle_time;

/*
- * 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;
@@ -493,8 +493,12 @@ struct bfq_io_cq {
uint64_t blkcg_serial_nr; /* the current blkcg serial */
#endif

- /* persistent data for associated synchronous process queue */
- struct bfq_iocq_bfqq_data bfqq_data;
+ /*
+ * Persistent data for associated synchronous process queues
+ * (one queue per actuator, see field bfqq above). In
+ * particular, each of these queues may undergo a merge.
+ */
+ struct bfq_iocq_bfqq_data bfqq_data[BFQ_MAX_ACTUATORS];

unsigned int requests; /* Number of requests this process has in flight */
};
--
2.20.1

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