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Subject[PATCH 18/18] io-controller: Debug hierarchical IO scheduling
Date
o Littile debugging aid for hierarchical IO scheduling.

o Enabled under CONFIG_DEBUG_GROUP_IOSCHED

o Currently it outputs more debug messages in blktrace output which helps
a great deal in debugging in hierarchical setup.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/Kconfig.iosched | 10 +++-
block/elevator-fq.c | 131 +++++++++++++++++++++++++++++++++++++++++++++++--
block/elevator-fq.h | 6 ++
3 files changed, 141 insertions(+), 6 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index 0677099..79f188c 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -140,6 +140,14 @@ config TRACK_ASYNC_CONTEXT
request, original owner of the bio is decided by using io tracking
patches otherwise we continue to attribute the request to the
submitting thread.
-endmenu

+config DEBUG_GROUP_IOSCHED
+ bool "Debug Hierarchical Scheduling support"
+ depends on CGROUPS && GROUP_IOSCHED
+ default n
+ ---help---
+ Enable some debugging hooks for hierarchical scheduling support.
+ Currently it just outputs more information in blktrace output.
+
+endmenu
endif
diff --git a/block/elevator-fq.c b/block/elevator-fq.c
index 1dd0bb3..9500619 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -30,7 +30,7 @@ static int elv_rate_sampling_window = HZ / 10;
#define IO_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE

#define IO_SERVICE_TREE_INIT ((struct io_service_tree) \
- { RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
+ { RB_ROOT, RB_ROOT, 0, NULL, NULL, 0, 0 })

static inline struct io_queue *elv_close_cooperator(struct request_queue *q,
struct io_queue *ioq, int probe);
@@ -118,6 +118,37 @@ static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
iog = container_of(entity, struct io_group, entity);
return iog;
}
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+static void io_group_path(struct io_group *iog, char *buf, int buflen)
+{
+ unsigned short id = iog->iocg_id;
+ struct cgroup_subsys_state *css;
+
+ rcu_read_lock();
+
+ if (!id)
+ goto out;
+
+ css = css_lookup(&io_subsys, id);
+ if (!css)
+ goto out;
+
+ if (!css_tryget(css))
+ goto out;
+
+ cgroup_path(css->cgroup, buf, buflen);
+
+ css_put(css);
+
+ rcu_read_unlock();
+ return;
+out:
+ rcu_read_unlock();
+ buf[0] = '\0';
+ return;
+}
+#endif
#else /* GROUP_IOSCHED */
#define for_each_entity(entity) \
for (; entity != NULL; entity = NULL)
@@ -372,7 +403,7 @@ static void bfq_active_insert(struct io_service_tree *st,
struct rb_node *node = &entity->rb_node;

bfq_insert(&st->active, entity);
-
+ st->nr_active++;
if (node->rb_left != NULL)
node = node->rb_left;
else if (node->rb_right != NULL)
@@ -434,7 +465,7 @@ static void bfq_active_extract(struct io_service_tree *st,

node = bfq_find_deepest(&entity->rb_node);
bfq_extract(&st->active, entity);
-
+ st->nr_active--;
if (node != NULL)
bfq_update_active_tree(node);
}
@@ -1233,6 +1264,9 @@ struct io_group *io_group_chain_alloc(struct request_queue *q, void *key,

io_group_init_entity(iocg, iog);
iog->my_entity = &iog->entity;
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ iog->iocg_id = css_id(&iocg->css);
+#endif

blk_init_request_list(&iog->rl);

@@ -1506,6 +1540,9 @@ struct io_group *io_alloc_root_group(struct request_queue *q,
/* elevator reference. */
elv_get_iog(iog);
hlist_add_head_rcu(&iog->group_node, &iocg->group_data);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ iog->iocg_id = css_id(&iocg->css);
+#endif
spin_unlock_irq(&iocg->lock);

return iog;
@@ -1886,6 +1923,7 @@ struct cgroup_subsys io_subsys = {
.destroy = iocg_destroy,
.populate = iocg_populate,
.subsys_id = io_subsys_id,
+ .use_id = 1,
};

/*
@@ -2203,6 +2241,25 @@ EXPORT_SYMBOL(elv_get_slice_idle);
void elv_ioq_served(struct io_queue *ioq, bfq_service_t served)
{
entity_served(&ioq->entity, served, ioq->nr_sectors);
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ struct elv_fq_data *efqd = ioq->efqd;
+ char path[128];
+ struct io_group *iog = ioq_to_io_group(ioq);
+ io_group_path(iog, path, sizeof(path));
+ elv_log_ioq(efqd, ioq, "ioq served: QSt=0x%lx QSs=0x%lx"
+ " QTt=0x%lx QTs=0x%lx grp=%s GTt=0x%lx "
+ " GTs=0x%lx rq_queued=%d",
+ served, ioq->nr_sectors,
+ ioq->entity.total_service,
+ ioq->entity.total_sector_service,
+ path,
+ iog->entity.total_service,
+ iog->entity.total_sector_service,
+ ioq->nr_queued);
+ }
+#endif
}

/* Tells whether ioq is queued in root group or not */
@@ -2671,11 +2728,34 @@ static void __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq,

if (ioq) {
struct io_group *iog = ioq_to_io_group(ioq);
+
elv_log_ioq(efqd, ioq, "set_active, busy=%d ioprio=%d"
- " weight=%ld group_weight=%ld",
+ " weight=%ld rq_queued=%d group_weight=%ld",
efqd->busy_queues,
ioq->entity.ioprio, ioq->entity.weight,
- iog_weight(iog));
+ ioq->nr_queued, iog_weight(iog));
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ char path[128];
+ struct io_service_tree *grpst;
+ int nr_active = 0;
+ if (iog != efqd->root_group) {
+ grpst = io_entity_service_tree(
+ &iog->entity);
+ nr_active = grpst->nr_active;
+ }
+ io_group_path(iog, path, sizeof(path));
+ elv_log_ioq(efqd, ioq, "set_active, ioq grp=%s"
+ " nrgrps=%d QTt=0x%lx QTs=0x%lx GTt=0x%lx "
+ " GTs=0x%lx rq_queued=%d", path, nr_active,
+ ioq->entity.total_service,
+ ioq->entity.total_sector_service,
+ iog->entity.total_service,
+ iog->entity.total_sector_service,
+ ioq->nr_queued);
+ }
+#endif
ioq->slice_end = 0;

elv_clear_ioq_wait_request(ioq);
@@ -2764,6 +2844,22 @@ void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
efqd->busy_queues++;
if (elv_ioq_class_rt(ioq))
efqd->busy_rt_queues++;
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ char path[128];
+ struct io_group *iog = ioq_to_io_group(ioq);
+ io_group_path(iog, path, sizeof(path));
+ elv_log(efqd, "add to busy: QTt=0x%lx QTs=0x%lx "
+ "ioq grp=%s GTt=0x%lx GTs=0x%lx rq_queued=%d",
+ ioq->entity.total_service,
+ ioq->entity.total_sector_service,
+ path,
+ iog->entity.total_service,
+ iog->entity.total_sector_service,
+ ioq->nr_queued);
+ }
+#endif
}

void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,
@@ -2773,7 +2869,24 @@ void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq,

BUG_ON(!elv_ioq_busy(ioq));
BUG_ON(ioq->nr_queued);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ char path[128];
+ struct io_group *iog = ioq_to_io_group(ioq);
+ io_group_path(iog, path, sizeof(path));
+ elv_log_ioq(efqd, ioq, "del from busy: QTt=0x%lx "
+ "QTs=0x%lx ioq grp=%s GTt=0x%lx GTs=0x%lx "
+ "rq_queued=%d",
+ ioq->entity.total_service,
+ ioq->entity.total_sector_service,
+ path,
+ iog->entity.total_service,
+ iog->entity.total_sector_service,
+ ioq->nr_queued);
+ }
+#else
elv_log_ioq(efqd, ioq, "del from busy");
+#endif
elv_clear_ioq_busy(ioq);
BUG_ON(efqd->busy_queues == 0);
efqd->busy_queues--;
@@ -3000,6 +3113,14 @@ void elv_ioq_request_add(struct request_queue *q, struct request *rq)

elv_ioq_update_io_thinktime(ioq);
elv_ioq_update_idle_window(q->elevator, ioq, rq);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ char path[128];
+ io_group_path(rq_iog(q, rq), path, sizeof(path));
+ elv_log_ioq(efqd, ioq, "add rq: group path=%s "
+ "rq_queued=%d", path, ioq->nr_queued);
+ }
+#endif

if (ioq == elv_active_ioq(q->elevator)) {
/*
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 42e3777..db3a347 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -43,6 +43,8 @@ struct io_service_tree {
struct rb_root active;
struct rb_root idle;

+ int nr_active;
+
struct io_entity *first_idle;
struct io_entity *last_idle;

@@ -245,6 +247,10 @@ struct io_group {

/* io group is going away */
int deleting;
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ unsigned short iocg_id;
+#endif
};

/**
--
1.6.0.1


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