[PATCH V13 3/8] block, bfq: move io_cq-persistent bfqq data into a dedicated struct

From: Paolo Valente
Date: Thu Dec 29 2022 - 15:38:10 EST

With a multi-actuator drive, a process may get associated with multiple
bfq_queues: one queue for each of the N actuators. So, the bfq_io_cq
data structure must be able to accommodate its per-queue persistent
information for N queues. Currently it stores this information for
just one queue, in several scalar fields.

This is a preparatory commit for moving to accommodating persistent
information for N queues. In particular, this commit packs all the
above scalar fields into a single data structure. Then there is now
only one field, in bfq_io_cq, that stores all the above information. This
scalar field will then be turned into an array by a following commit.

Suggested-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
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 | 138 +++++++++++++++++++++++++-------------------
block/bfq-iosched.h | 52 ++++++++++-------
2 files changed, 110 insertions(+), 80 deletions(-)

diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
index 54d629639c1b..af364a7336e5 100644
--- a/block/bfq-iosched.c
+++ b/block/bfq-iosched.c
@@ -395,10 +395,6 @@ void bic_set_bfqq(struct bfq_io_cq *bic,
{
struct bfq_queue *old_bfqq = bic->bfqq[is_sync][actuator_idx];

- /* Clear bic pointer if bfqq is detached from this bic */
- if (old_bfqq && old_bfqq->bic == bic)
- old_bfqq->bic = NULL;
-
/*
* If bfqq != NULL, then a non-stable queue merge between
* bic->bfqq and bfqq is happening here. This causes troubles
@@ -412,12 +408,18 @@ 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;
+
+ /* Clear bic pointer if bfqq is detached from this bic */
+ if (old_bfqq && old_bfqq->bic == bic)
+ old_bfqq->bic = NULL;
+
if (is_sync)
bic->bfqq[1][actuator_idx] = bfqq;
else
bic->bfqq[0][actuator_idx] = bfqq;

- if (bfqq && bic->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
@@ -426,9 +428,9 @@ 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(bfqq_data->stable_merge_bfqq);

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

@@ -1133,38 +1135,40 @@ 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);

- if (bic->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 (bic->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 = 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 = 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 = 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 = 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 = bic->saved_wr_coeff;
+ bfqq->wr_coeff = bfqq_data->saved_wr_coeff;
}
- 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 = 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;

if (bfqq->wr_coeff > 1 && (bfq_bfqq_in_large_burst(bfqq) ||
time_is_before_jiffies(bfqq->last_wr_start_finish +
@@ -1849,7 +1853,7 @@ 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)->bfqq_data.stably_merged) &&
(*interactive || soft_rt)));

/*
@@ -2849,6 +2853,7 @@ 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;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data;

/* if a merge has already been setup, then proceed with that first */
if (bfqq->new_bfqq)
@@ -2870,21 +2875,21 @@ 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) && 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 =
- bic->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);

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

if (!idling_boosts_thr_without_issues(bfqd, bfqq) &&
proc_ref > 0) {
@@ -2893,10 +2898,10 @@ 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;
+ bfqq_data->stably_merged = true;
if (new_bfqq->bic)
- new_bfqq->bic->stably_merged =
- true;
+ new_bfqq->bic->bfqq_data.stably_merged =
+ true;
}
return new_bfqq;
} else
@@ -2995,6 +3000,7 @@ 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;

/*
* If !bfqq->bic, the queue is already shared or its requests
@@ -3004,18 +3010,21 @@ 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);
+ 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 =
+ 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 =
+ !hlist_unhashed(&bfqq->burst_list_node);
+
if (unlikely(bfq_bfqq_just_created(bfqq) &&
!bfq_bfqq_in_large_burst(bfqq) &&
bfqq->bfqd->low_latency)) {
@@ -3028,17 +3037,21 @@ 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;
+ 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 =
+ bfq_wr_duration(bfqq->bfqd);
+ bfqq_data->saved_last_wr_start_finish = jiffies;
} else {
- bic->saved_wr_coeff = bfqq->wr_coeff;
- bic->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;
- 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;
+ bfqq_data->saved_service_from_wr =
+ bfqq->service_from_wr;
+ bfqq_data->saved_last_wr_start_finish =
+ bfqq->last_wr_start_finish;
+ bfqq_data->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
}
}

@@ -5364,6 +5377,7 @@ static void bfq_exit_icq(struct io_cq *icq)
* therefore on its unused per-actuator fields being NULL.
*/
unsigned int num_actuators = BFQ_MAX_ACTUATORS;
+ struct bfq_iocq_bfqq_data *bfqq_data = &bic->bfqq_data;

/*
* bfqd is NULL if scheduler already exited, and in that case
@@ -5374,8 +5388,8 @@ static void bfq_exit_icq(struct io_cq *icq)
num_actuators = bfqd->num_actuators;
}

- if (bic->stable_merge_bfqq)
- bfq_put_stable_ref(bic->stable_merge_bfqq);
+ 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++) {
bfq_exit_icq_bfqq(bic, true, act_idx);
@@ -5566,13 +5580,14 @@ bfq_do_early_stable_merge(struct bfq_data *bfqd, struct bfq_queue *bfqq,
{
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->stably_merged = true;
- bic->stably_merged = true;
+ new_bfqq->bic->bfqq_data.stably_merged = true;
+ bfqq_data->stably_merged = true;

/*
* Reusing merge functions. This implies that
@@ -5641,6 +5656,7 @@ 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
@@ -5702,7 +5718,7 @@ 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;
+ bfqq_data->stable_merge_bfqq = last_bfqq_created;
}
}

@@ -6623,6 +6639,7 @@ 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;

if (likely(bfqq && bfqq != &bfqd->oom_bfqq))
return bfqq;
@@ -6636,12 +6653,12 @@ 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 ((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 (bic->was_in_burst_list)
+ if (bfqq_data->was_in_burst_list)
/*
* If bfqq was in the current
* burst list before being
@@ -6730,6 +6747,7 @@ 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;

if (unlikely(!rq->elv.icq))
return NULL;
@@ -6753,15 +6771,17 @@ 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) &&
- !bic->stably_merged) {
+ !bfqq_data->stably_merged) {
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;
+ bfqq_data->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 3c6b21b2cd95..8e0215b8cc30 100644
--- a/block/bfq-iosched.h
+++ b/block/bfq-iosched.h
@@ -413,27 +413,9 @@ struct bfq_queue {
};

/**
- * struct bfq_io_cq - per (request_queue, io_context) structure.
- */
-struct bfq_io_cq {
- /* associated io_cq structure */
- struct io_cq icq; /* must be the first member */
- /*
- * Matrix of associated process queues: first row for async
- * queues, second row sync queues. Each row contains one
- * column for each actuator. An I/O request generated by the
- * process is inserted into the queue pointed by bfqq[i][j] if
- * the request is to be served by the j-th actuator of the
- * drive, where i==0 or i==1, depending on whether the request
- * is async or sync. So there is a distinct queue for each
- * actuator.
- */
- struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS];
- /* per (request_queue, blkcg) ioprio */
- int ioprio;
-#ifdef CONFIG_BFQ_GROUP_IOSCHED
- uint64_t blkcg_serial_nr; /* the current blkcg serial */
-#endif
+* struct bfq_data - bfqq data unique and persistent for associated bfq_io_cq
+*/
+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
@@ -488,6 +470,34 @@ struct bfq_io_cq {
struct bfq_queue *stable_merge_bfqq;

bool stably_merged; /* non splittable if true */
+};
+
+/**
+ * struct bfq_io_cq - per (request_queue, io_context) structure.
+ */
+struct bfq_io_cq {
+ /* associated io_cq structure */
+ struct io_cq icq; /* must be the first member */
+ /*
+ * Matrix of associated process queues: first row for async
+ * queues, second row sync queues. Each row contains one
+ * column for each actuator. An I/O request generated by the
+ * process is inserted into the queue pointed by bfqq[i][j] if
+ * the request is to be served by the j-th actuator of the
+ * drive, where i==0 or i==1, depending on whether the request
+ * is async or sync. So there is a distinct queue for each
+ * actuator.
+ */
+ struct bfq_queue *bfqq[2][BFQ_MAX_ACTUATORS];
+ /* per (request_queue, blkcg) ioprio */
+ int ioprio;
+#ifdef CONFIG_BFQ_GROUP_IOSCHED
+ uint64_t blkcg_serial_nr; /* the current blkcg serial */
+#endif
+
+ /* persistent data for associated synchronous process queue */
+ struct bfq_iocq_bfqq_data bfqq_data;
+
unsigned int requests; /* Number of requests this process has in flight */
};

--
2.20.1