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Subject[PATCH 10/23] 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. It also creates additional
cgroup interfaces io.disk_queue and io.disk_dequeue to output some more
debugging data.

Signed-off-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
---
block/Kconfig.iosched | 8 +++
block/elevator-fq.c | 168 ++++++++++++++++++++++++++++++++++++++++++++++++-
block/elevator-fq.h | 29 +++++++++
3 files changed, 202 insertions(+), 3 deletions(-)

diff --git a/block/Kconfig.iosched b/block/Kconfig.iosched
index a91a807..a7d0bf8 100644
--- a/block/Kconfig.iosched
+++ b/block/Kconfig.iosched
@@ -90,6 +90,14 @@ config DEFAULT_IOSCHED
default "cfq" if DEFAULT_CFQ
default "noop" if DEFAULT_NOOP

+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 563db2d..cb348fa 100644
--- a/block/elevator-fq.c
+++ b/block/elevator-fq.c
@@ -251,6 +251,91 @@ init_io_entity_service_tree(struct io_entity *entity, struct io_entity *parent)
entity->st = &parent_iog->sched_data.service_tree[idx];
}

+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+static void io_group_path(struct io_group *iog)
+{
+ 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, iog->path, sizeof(iog->path));
+
+ css_put(css);
+
+ rcu_read_unlock();
+ return;
+out:
+ rcu_read_unlock();
+ iog->path[0] = '\0';
+ return;
+}
+
+static inline void debug_update_stats_enqueue(struct io_entity *entity)
+{
+ struct io_group *iog = iog_of(entity);
+
+ if (iog) {
+ struct elv_fq_data *efqd;
+
+ /*
+ * Keep track of how many times a group has been added
+ * to active tree.
+ */
+ iog->queue++;
+
+ rcu_read_lock();
+ efqd = rcu_dereference(iog->key);
+ if (efqd)
+ elv_log_iog(efqd, iog, "add group weight=%u",
+ iog->entity.weight);
+ rcu_read_unlock();
+ }
+}
+
+static inline void debug_update_stats_dequeue(struct io_entity *entity)
+{
+ struct io_group *iog = iog_of(entity);
+
+ if (iog) {
+ struct elv_fq_data *efqd;
+
+ iog->dequeue++;
+ rcu_read_lock();
+ efqd = rcu_dereference(iog->key);
+ if (efqd)
+ elv_log_iog(efqd, iog, "del group weight=%u",
+ iog->entity.weight);
+ rcu_read_unlock();
+ }
+}
+
+static inline void print_ioq_service_stats(struct io_queue *ioq)
+{
+ struct io_group *iog = ioq_to_io_group(ioq);
+
+ elv_log_ioq(ioq->efqd, ioq, "service: QTt=%lu QTs=%lu GTt=%lu GTs=%lu",
+ ioq->entity.total_time, ioq->entity.total_sectors,
+ iog->entity.total_time, iog->entity.total_sectors);
+}
+
+#else /* DEBUG_GROUP_IOSCHED */
+static inline void io_group_path(struct io_group *iog) {}
+static inline void print_ioq_service_stats(struct io_queue *ioq) {}
+static inline void debug_update_stats_enqueue(struct io_entity *entity) {}
+static inline void debug_update_stats_dequeue(struct io_entity *entity) {}
+#endif /* DEBUG_GROUP_IOSCHED */
+
static void
entity_served(struct io_entity *entity, unsigned long served,
unsigned long nr_sectors)
@@ -338,6 +423,7 @@ static void dequeue_io_entity(struct io_entity *entity)
entity->on_st = 0;
st->nr_active--;
sd->nr_active--;
+ debug_update_stats_dequeue(entity);
}

static void
@@ -386,6 +472,7 @@ static void enqueue_io_entity(struct io_entity *entity)
entity->on_st = 1;
place_entity(st, entity, 0);
__enqueue_io_entity(st, entity, 0);
+ debug_update_stats_enqueue(entity);
}

static struct io_entity *__lookup_next_io_entity(struct io_service_tree *st)
@@ -544,6 +631,9 @@ EXPORT_SYMBOL(elv_put_ioq);
static void elv_ioq_served(struct io_queue *ioq, unsigned long served)
{
entity_served(&ioq->entity, served, ioq->nr_sectors);
+ elv_log_ioq(ioq->efqd, ioq, "ioq served: QSt=%lu QSs=%lu qued=%lu",
+ served, ioq->nr_sectors, ioq->nr_queued);
+ print_ioq_service_stats(ioq);
}

/*
@@ -797,7 +887,6 @@ io_cgroup_lookup_group(struct io_cgroup *iocg, void *key)
return NULL;
}

-
#define SHOW_FUNCTION(__VAR) \
static u64 io_cgroup_##__VAR##_read(struct cgroup *cgroup, \
struct cftype *cftype) \
@@ -917,6 +1006,64 @@ 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);
+ rcu_read_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->queue);
+ }
+ rcu_read_unlock();
+ 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
+
struct cftype io_files[] = {
{
.name = "weight",
@@ -936,6 +1083,16 @@ struct cftype io_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
};

static int iocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
@@ -1063,6 +1220,7 @@ io_group_chain_alloc(struct request_queue *q, void *key, struct cgroup *cgroup)
* or cgroup deletion path depending on who is exiting first.
*/
elv_get_iog(iog);
+ io_group_path(iog);

if (leaf == NULL) {
leaf = iog;
@@ -1237,6 +1395,7 @@ static struct io_group *io_alloc_root_group(struct request_queue *q,
hlist_add_head_rcu(&iog->group_node, &iocg->group_data);
iog->iocg_id = css_id(&iocg->css);
spin_unlock_irq(&iocg->lock);
+ io_group_path(iog);

return iog;
}
@@ -1523,6 +1682,7 @@ __elv_set_active_ioq(struct elv_fq_data *efqd, struct io_queue *ioq, int coop)
efqd->busy_queues, ioq->entity.ioprio_class,
ioq->entity.ioprio, ioq->entity.weight,
iog_weight(iog), ioq->nr_queued);
+ print_ioq_service_stats(ioq);

ioq->slice_start = ioq->slice_end = 0;
ioq->dispatch_start = jiffies;
@@ -1581,10 +1741,11 @@ static void elv_add_ioq_busy(struct elv_fq_data *efqd, struct io_queue *ioq)
{
BUG_ON(elv_ioq_busy(ioq));
BUG_ON(ioq == efqd->active_queue);
- elv_log_ioq(efqd, ioq, "add to busy");
enqueue_ioq(ioq);
elv_mark_ioq_busy(ioq);
efqd->busy_queues++;
+ elv_log_ioq(efqd, ioq, "add to busy: qued=%d", ioq->nr_queued);
+ print_ioq_service_stats(ioq);
}

static void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq)
@@ -1593,7 +1754,8 @@ static void elv_del_ioq_busy(struct elevator_queue *e, struct io_queue *ioq)

BUG_ON(!elv_ioq_busy(ioq));
BUG_ON(ioq->nr_queued);
- elv_log_ioq(efqd, ioq, "del from busy");
+ elv_log_ioq(efqd, ioq, "del from busy: qued=%d", ioq->nr_queued);
+ print_ioq_service_stats(ioq);
elv_clear_ioq_busy(ioq);
BUG_ON(efqd->busy_queues == 0);
efqd->busy_queues--;
diff --git a/block/elevator-fq.h b/block/elevator-fq.h
index 9757e39..154014c 100644
--- a/block/elevator-fq.h
+++ b/block/elevator-fq.h
@@ -114,6 +114,16 @@ struct io_group {

/* The device MKDEV(major, minor), this group has been created for */
dev_t dev;
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+ /* How many times this group has been added to active tree */
+ unsigned long queue;
+
+ /* How many times this group has been removed from active tree */
+ unsigned long dequeue;
+
+ /* Store cgroup path */
+ char path[128];
+#endif
};

struct io_cgroup {
@@ -170,10 +180,29 @@ struct elv_fq_data {
};

/* Logging facilities. */
+#ifdef CONFIG_DEBUG_GROUP_IOSCHED
+#define elv_log_ioq(efqd, ioq, fmt, args...) \
+{ \
+ blk_add_trace_msg((efqd)->queue, "elv%d%c %s " fmt, (ioq)->pid, \
+ elv_ioq_sync(ioq) ? 'S' : 'A', \
+ ioq_to_io_group(ioq)->path, ##args); \
+}
+
+#define elv_log_iog(efqd, iog, fmt, args...) \
+{ \
+ blk_add_trace_msg((efqd)->queue, "elv %s " fmt, (iog)->path, ##args); \
+}
+
+#else
#define elv_log_ioq(efqd, ioq, fmt, args...) \
blk_add_trace_msg((efqd)->queue, "elv%d%c " fmt, (ioq)->pid, \
elv_ioq_sync(ioq) ? 'S' : 'A', ##args)

+#define elv_log_iog(efqd, iog, fmt, args...) \
+ blk_add_trace_msg((efqd)->queue, "elv " fmt, ##args)
+
+#endif
+
#define elv_log(efqd, fmt, args...) \
blk_add_trace_msg((efqd)->queue, "elv " fmt, ##args)

--
1.6.0.6


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