[PATCH 19/20] io-controller: Debug hierarchical IO scheduling

Vivek Goyal
2009-05-26T22:44:56Z

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. It also creates additional
cgroup interfaces io.disk_queue and io.disk_dequeue to output some more
debugging data.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/Kconfig.iosched | 10 ++-
block/elevator-fq.c | 298 ++++++++++++++++++++++++++++++++++++++++++++++++-
block/elevator-fq.h | 14 +++
3 files changed, 318 insertions(+), 4 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 6d97ad9..6dd8683 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -115,6 +115,126 @@ static inline int iog_deleting(struct io_group *iog)
return iog->deleting;
}

+static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
+{
+ struct io_group *iog = NULL;
+
+ BUG_ON(entity == NULL);
+ if (entity->my_sched_data != NULL)
+ iog = container_of(entity, struct io_group, entity);
+ return iog;
+}
+
+/* Returns parent group of io group */
+static inline struct io_group *iog_parent(struct io_group *iog)
+{
+ struct io_group *piog;
+
+ if (!iog->entity.sched_data)
+ return NULL;
+
+ /*
+ * Not following entity->parent pointer as for top level groups
+ * this pointer is NULL.
+ */
+ piog = container_of(iog->entity.sched_data, struct io_group,
+ sched_data);
+ return piog;
+}
+
+#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;
+}
+
+/*
+ * An entity has been freshly added to active tree. Either it came from
+ * idle tree or it was not on any of the trees. Do the accounting.
+ */
+static inline void bfq_account_for_entity_addition(struct io_entity *entity)
+{
+ struct io_group *iog = io_entity_to_iog(entity);
+
+ if (iog) {
+ struct elv_fq_data *efqd;
+ char path[128];
+
+ /*
+ * Keep track of how many times a group has been removed
+ * from active tree because it did not have any active
+ * backlogged ioq under it
+ */
+ iog->queue++;
+ iog->queue_start = jiffies;
+
+ /* Log group addition event */
+ rcu_read_lock();
+ efqd = rcu_dereference(iog->key);
+ if (efqd) {
+ io_group_path(iog, path, sizeof(path));
+ elv_log(efqd, "add group=%s weight=%ld", path,
+ iog->entity.weight);
+ }
+ rcu_read_unlock();
+ }
+}
+
+/*
+ * An entity got removed from active tree and either went to idle tree or
+ * not is on any of the tree. Do the accouting
+ */
+static inline void bfq_account_for_entity_deletion(struct io_entity *entity)
+{
+ struct io_group *iog = io_entity_to_iog(entity);
+
+ if (iog) {
+ struct elv_fq_data *efqd;
+ char path[128];
+
+ iog->dequeue++;
+ /* Keep a track of how long group was on active tree */
+ iog->queue_duration += jiffies_to_msecs(jiffies -
+ iog->queue_start);
+ iog->queue_start = 0;
+
+ /* Log group deletion event */
+ rcu_read_lock();
+ efqd = rcu_dereference(iog->key);
+ if (efqd) {
+ io_group_path(iog, path, sizeof(path));
+ elv_log(efqd, "del group=%s weight=%ld", path,
+ iog->entity.weight);
+ }
+ rcu_read_unlock();
+ }
+}
+#endif
+
#else /* GROUP_IOSCHED */
#define for_each_entity(entity) \
for (; entity != NULL; entity = NULL)
@@ -137,6 +257,12 @@ static inline int iog_deleting(struct io_group *iog)
/* In flat mode, root cgroup can't be deleted. */
return 0;
}
+
+static inline struct io_group *io_entity_to_iog(struct io_entity *entity)
+{
+ return NULL;
+}
+
#endif

/*
@@ -570,6 +696,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
{
struct io_sched_data *sd = entity->sched_data;
struct io_service_tree *st = io_entity_service_tree(entity);
+ int newly_added = 0;

if (entity == sd->active_entity) {
BUG_ON(entity->tree != NULL);
@@ -596,6 +723,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
bfq_idle_extract(st, entity);
entity->start = bfq_gt(st->vtime, entity->finish) ?
st->vtime : entity->finish;
+ newly_added = 1;
} else {
/*
* The finish time of the entity may be invalid, and
@@ -608,6 +736,7 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)

BUG_ON(entity->on_st);
entity->on_st = 1;
+ newly_added = 1;
}

st = __bfq_entity_update_prio(st, entity);
@@ -645,6 +774,10 @@ static void __bfq_activate_entity(struct io_entity *entity, int add_front)
bfq_calc_finish(entity, entity->budget);
}
bfq_active_insert(st, entity);
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ if (newly_added)
+ bfq_account_for_entity_addition(entity);
+#endif
}

/**
@@ -715,6 +848,9 @@ int __bfq_deactivate_entity(struct io_entity *entity, int requeue)
BUG_ON(sd->active_entity == entity);
BUG_ON(sd->next_active == entity);

+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ bfq_account_for_entity_deletion(entity);
+#endif
return ret;
}

@@ -1205,6 +1341,67 @@ static int io_cgroup_disk_sectors_read(struct cgroup *cgroup,
return 0;
}

+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+static int io_cgroup_disk_queue_read(struct cgroup *cgroup,
+ struct cftype *cftype, struct seq_file *m)
+{
+ struct io_cgroup *iocg = NULL;
+ struct io_group *iog = NULL;
+ struct hlist_node *n;
+
+ if (!cgroup_lock_live_group(cgroup))
+ return -ENODEV;
+
+ iocg = cgroup_to_io_cgroup(cgroup);
+ spin_lock_irq(&iocg->lock);
+ /* Loop through all the io groups and print statistics */
+ hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+ /*
+ * There might be groups which are not functional and
+ * waiting to be reclaimed upon cgoup deletion.
+ */
+ if (iog->key) {
+ seq_printf(m, "%u %u %lu %lu\n", MAJOR(iog->dev),
+ MINOR(iog->dev), iog->queue,
+ iog->queue_duration);
+ }
+ }
+ spin_unlock_irq(&iocg->lock);
+ cgroup_unlock();
+
+ return 0;
+}
+
+static int io_cgroup_disk_dequeue_read(struct cgroup *cgroup,
+ struct cftype *cftype, struct seq_file *m)
+{
+ struct io_cgroup *iocg = NULL;
+ struct io_group *iog = NULL;
+ struct hlist_node *n;
+
+ if (!cgroup_lock_live_group(cgroup))
+ return -ENODEV;
+
+ iocg = cgroup_to_io_cgroup(cgroup);
+ spin_lock_irq(&iocg->lock);
+ /* Loop through all the io groups and print statistics */
+ hlist_for_each_entry_rcu(iog, n, &iocg->group_data, group_node) {
+ /*
+ * There might be groups which are not functional and
+ * waiting to be reclaimed upon cgoup deletion.
+ */
+ if (iog->key) {
+ seq_printf(m, "%u %u %lu\n", MAJOR(iog->dev),
+ MINOR(iog->dev), iog->dequeue);
+ }
+ }
+ spin_unlock_irq(&iocg->lock);
+ cgroup_unlock();
+
+ return 0;
+}
+#endif
+
/**
* bfq_group_chain_alloc - allocate a chain of groups.
* @bfqd: queue descriptor.
@@ -1754,6 +1951,16 @@ struct cftype bfqio_files[] = {
.name = "disk_sectors",
.read_seq_string = io_cgroup_disk_sectors_read,
},
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ {
+ .name = "disk_queue",
+ .read_seq_string = io_cgroup_disk_queue_read,
+ },
+ {
+ .name = "disk_dequeue",
+ .read_seq_string = io_cgroup_disk_dequeue_read,
+ },
+#endif
};

int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
@@ -2078,6 +2285,7 @@ struct cgroup_subsys io_subsys = {
.destroy = iocg_destroy,
.populate = iocg_populate,
.subsys_id = io_subsys_id,
+ .use_id = 1,
};

/*
@@ -2361,6 +2569,25 @@ 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 */
@@ -2835,10 +3062,32 @@ 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];
+ int nr_active = 0;
+ struct io_group *parent = NULL;
+
+ parent = iog_parent(iog);
+ if (parent)
+ nr_active = elv_iog_nr_active(parent);
+
+ 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);
@@ -2920,6 +3169,22 @@ 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,
@@ -2929,7 +3194,24 @@ 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--;
@@ -3157,6 +3439,16 @@ 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];
+ struct io_group *iog = ioq_to_io_group(ioq);
+
+ io_group_path(iog, 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)) {
/*
@@ -3364,7 +3656,7 @@ void *elv_fq_select_ioq(struct request_queue *q, int force)
}

/* We are waiting for this queue to become busy before it expires.*/
- if (efqd->fairness && elv_ioq_wait_busy(ioq)) {
+ if (elv_ioq_wait_busy(ioq)) {
ioq = NULL;
goto keep_queue;
}
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 9062bfd..de0f6b0 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -249,6 +249,20 @@ struct io_group {

/* request list associated with the group */
struct request_list rl;
+
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ /* How many times this group has been added to active tree */
+ unsigned long queue;
+
+ /* How long this group remained on active tree, in ms */
+ unsigned long queue_duration;
+
+ /* When was this group added to active tree */
+ unsigned long queue_start;
+
+ /* How many times this group has been removed from active tree */
+ unsigned long dequeue;
+#endif
};

struct io_policy_node {
--
1.6.0.1