blkio: Export disk time and sectors used by a group to user space

o Export disk time and sector used by a group to user space through cgroup
  interface.

o Also export a "dequeue" interface to cgroup which keeps track of how many
  a times a group was deleted from service tree. Helps in debugging.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 99 insertions, 6 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 6bc99a3865b0..4ef78d35cbd2 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -11,6 +11,8 @@
  *                    Nauman Rafique <nauman@google.com>
  */
 #include <linux/ioprio.h>
+#include <linux/seq_file.h>
+#include <linux/kdev_t.h>
 #include "blk-cgroup.h"
 
 extern void cfq_unlink_blkio_group(void *, struct blkio_group *);
@@ -23,8 +25,15 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
                             struct blkio_cgroup, css);
 }
 
+void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
+                        unsigned long time, unsigned long sectors)
+{
+        blkg->time += time;
+        blkg->sectors += sectors;
+}
+
 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-                                struct blkio_group *blkg, void *key)
+                        struct blkio_group *blkg, void *key, dev_t dev)
 {
         unsigned long flags;
 
@@ -37,6 +46,7 @@ void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
         /* Need to take css reference ? */
         cgroup_path(blkcg->css.cgroup, blkg->path, sizeof(blkg->path));
 #endif
+        blkg->dev = dev;
 }
 
 static void __blkiocg_del_blkio_group(struct blkio_group *blkg)
@@ -115,12 +125,64 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         return 0;
 }
 
+#define SHOW_FUNCTION_PER_GROUP(__VAR)                                  \
+static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
+                        struct cftype *cftype, struct seq_file *m)      \
+{                                                                       \
+        struct blkio_cgroup *blkcg;                                     \
+        struct blkio_group *blkg;                                       \
+        struct hlist_node *n;                                           \
+                                                                        \
+        if (!cgroup_lock_live_group(cgroup))                            \
+                return -ENODEV;                                         \
+                                                                        \
+        blkcg = cgroup_to_blkio_cgroup(cgroup);                         \
+        rcu_read_lock();                                                \
+        hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
+                if (blkg->dev)                                          \
+                        seq_printf(m, "%u:%u %lu\n", MAJOR(blkg->dev),  \
+                                 MINOR(blkg->dev), blkg->__VAR);        \
+        }                                                               \
+        rcu_read_unlock();                                              \
+        cgroup_unlock();                                                \
+        return 0;                                                       \
+}
+
+SHOW_FUNCTION_PER_GROUP(time);
+SHOW_FUNCTION_PER_GROUP(sectors);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+SHOW_FUNCTION_PER_GROUP(dequeue);
+#endif
+#undef SHOW_FUNCTION_PER_GROUP
+
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
+                        unsigned long dequeue)
+{
+        blkg->dequeue += dequeue;
+}
+#endif
+
 struct cftype blkio_files[] = {
         {
                 .name = "weight",
                 .read_u64 = blkiocg_weight_read,
                 .write_u64 = blkiocg_weight_write,
         },
+        {
+                .name = "time",
+                .read_seq_string = blkiocg_time_read,
+        },
+        {
+                .name = "sectors",
+                .read_seq_string = blkiocg_sectors_read,
+        },
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+       {
+                .name = "dequeue",
+                .read_seq_string = blkiocg_dequeue_read,
+       },
+#endif
 };
 
 static int blkiocg_populate(struct cgroup_subsys *subsys, struct cgroup *cgroup)
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 3573199b298b..b24ab71db826 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -30,7 +30,15 @@ struct blkio_group {
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* Store cgroup path */
         char path[128];
+        /* How many times this group has been removed from service tree */
+        unsigned long dequeue;
 #endif
+        /* The device MKDEV(major, minor), this group has been created for */
+        dev_t   dev;
+
+        /* total disk time and nr sectors dispatched by this group */
+        unsigned long time;
+        unsigned long sectors;
 };
 
 #define BLKIO_WEIGHT_MIN        100
@@ -42,24 +50,30 @@ static inline char *blkg_path(struct blkio_group *blkg)
 {
         return blkg->path;
 }
+void blkiocg_update_blkio_group_dequeue_stats(struct blkio_group *blkg,
+                                unsigned long dequeue);
 #else
 static inline char *blkg_path(struct blkio_group *blkg) { return NULL; }
+static inline void blkiocg_update_blkio_group_dequeue_stats(
+                        struct blkio_group *blkg, unsigned long dequeue) {}
 #endif
 
 #ifdef CONFIG_BLK_CGROUP
 extern struct blkio_cgroup blkio_root_cgroup;
 extern struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup);
 extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-                                struct blkio_group *blkg, void *key);
+                        struct blkio_group *blkg, void *key, dev_t dev);
 extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
                                                 void *key);
+void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
+                        unsigned long time, unsigned long sectors);
 #else
 static inline struct blkio_cgroup *
 cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
 
 static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-                        struct blkio_group *blkg, void *key)
+                        struct blkio_group *blkg, void *key, dev_t dev)
 {
 }
 
@@ -68,5 +82,9 @@ blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }
 
 static inline struct blkio_group *
 blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; }
+static inline void blkiocg_update_blkio_group_stats(struct blkio_group *blkg,
+                        unsigned long time, unsigned long sectors)
+{
+}
 #endif
 #endif /* _BLK_CGROUP_H */
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 662d4e55b3c2..7d345e772d88 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -143,6 +143,8 @@ struct cfq_queue {
         struct cfq_rb_root *service_tree;
         struct cfq_queue *new_cfqq;
         struct cfq_group *cfqg;
+        /* Sectors dispatched in current dispatch round */
+        unsigned long nr_sectors;
 };
 
 /*
@@ -852,6 +854,7 @@ cfq_group_service_tree_del(struct cfq_data *cfqd, struct cfq_group *cfqg)
         if (!RB_EMPTY_NODE(&cfqg->rb_node))
                 cfq_rb_erase(&cfqg->rb_node, st);
         cfqg->saved_workload_slice = 0;
+        blkiocg_update_blkio_group_dequeue_stats(&cfqg->blkg, 1);
 }
 
 static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
@@ -878,7 +881,8 @@ static inline unsigned int cfq_cfqq_slice_usage(struct cfq_queue *cfqq)
                         slice_used = allocated_slice;
         }
 
-        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u", slice_used);
+        cfq_log_cfqq(cfqq->cfqd, cfqq, "sl_used=%u sect=%lu", slice_used,
+                                cfqq->nr_sectors);
         return slice_used;
 }
 
@@ -906,6 +910,8 @@ static void cfq_group_served(struct cfq_data *cfqd, struct cfq_group *cfqg,
 
         cfq_log_cfqg(cfqd, cfqg, "served: vt=%llu min_vt=%llu", cfqg->vdisktime,
                                         st->min_vdisktime);
+        blkiocg_update_blkio_group_stats(&cfqg->blkg, used_sl,
+                                                cfqq->nr_sectors);
 }
 
 #ifdef CONFIG_CFQ_GROUP_IOSCHED
@@ -924,6 +930,8 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
         void *key = cfqd;
         int i, j;
         struct cfq_rb_root *st;
+        struct backing_dev_info *bdi = &cfqd->queue->backing_dev_info;
+        unsigned int major, minor;
 
         /* Do we need to take this reference */
         if (!css_tryget(&blkcg->css))
@@ -951,7 +959,9 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
         atomic_set(&cfqg->ref, 1);
 
         /* Add group onto cgroup list */
-        blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd);
+        sscanf(dev_name(bdi->dev), "%u:%u", &major, &minor);
+        blkiocg_add_blkio_group(blkcg, &cfqg->blkg, (void *)cfqd,
+                                        MKDEV(major, minor));
 
         /* Add group on cfqd list */
         hlist_add_head(&cfqg->cfqd_node, &cfqd->cfqg_list);
@@ -1478,6 +1488,7 @@ static void __cfq_set_active_queue(struct cfq_data *cfqd,
                 cfqq->dispatch_start = jiffies;
                 cfqq->slice_end = 0;
                 cfqq->slice_dispatch = 0;
+                cfqq->nr_sectors = 0;
 
                 cfq_clear_cfqq_wait_request(cfqq);
                 cfq_clear_cfqq_must_dispatch(cfqq);
@@ -1801,6 +1812,7 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
 
         if (cfq_cfqq_sync(cfqq))
                 cfqd->sync_flight++;
+        cfqq->nr_sectors += blk_rq_sectors(rq);
 }
 
 /*
@@ -3513,7 +3525,8 @@ static void *cfq_init_queue(struct request_queue *q)
          * to make sure that cfq_put_cfqg() does not try to kfree root group
          */
         atomic_set(&cfqg->ref, 1);
-        blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd);
+        blkiocg_add_blkio_group(&blkio_root_cgroup, &cfqg->blkg, (void *)cfqd,
+                                        0);
 #endif
         /*
          * Not strictly needed (since RB_ROOT just clears the node and we