blkio: Changes to IO controller additional stats patches

that include some minor fixes and addresses all comments.

Changelog: (most based on Vivek Goyal's comments)
o renamed blkiocg_reset_write to blkiocg_reset_stats
o more clarification in the documentation on io_service_time and io_wait_time
o Initialize blkg->stats_lock
o rename io_add_stat to blkio_add_stat and declare it static
o use bool for direction and sync
o derive direction and sync info from existing rq methods
o use 12 for major:minor string length
o define io_service_time better to cover the NCQ case
o add a separate reset_stats interface
o make the indexed stats a 2d array to simplify macro and function pointer code
o blkio.time now exports in jiffies as before
o Added stats description in patch description and
  Documentation/cgroup/blkio-controller.txt
o Prefix all stats functions with blkio and make them static as applicable
o replace IO_TYPE_MAX with IO_TYPE_TOTAL
o Moved #define constant to top of blk-cgroup.c
o Pass dev_t around instead of char *
o Add note to documentation file about resetting stats
o use BLK_CGROUP_MODULE in addition to BLK_CGROUP config option in #ifdef
  statements
o Avoid struct request specific knowledge in blk-cgroup. blk-cgroup.h now has
  rq_direction() and rq_sync() functions which are used by CFQ and when using
  io-controller at a higher level, bio_* functions can be added.

Signed-off-by: Divyesh Shah<dpshah@google.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

3 files changed, 133 insertions, 129 deletions

diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 9af7257f429c..6797df508821 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -18,6 +18,8 @@
 #include <linux/blkdev.h>
 #include "blk-cgroup.h"
 
+#define MAX_KEY_LEN 100
+
 static DEFINE_SPINLOCK(blkio_list_lock);
 static LIST_HEAD(blkio_list);
 
@@ -56,24 +58,27 @@ struct blkio_cgroup *cgroup_to_blkio_cgroup(struct cgroup *cgroup)
 }
 EXPORT_SYMBOL_GPL(cgroup_to_blkio_cgroup);
 
+void blkio_group_init(struct blkio_group *blkg)
+{
+        spin_lock_init(&blkg->stats_lock);
+}
+EXPORT_SYMBOL_GPL(blkio_group_init);
+
 /*
  * Add to the appropriate stat variable depending on the request type.
  * This should be called with the blkg->stats_lock held.
  */
-void io_add_stat(uint64_t *stat, uint64_t add, unsigned int flags)
+static void blkio_add_stat(uint64_t *stat, uint64_t add, bool direction,
+                                bool sync)
 {
-        if (flags & REQ_RW)
-                stat[IO_WRITE] += add;
+        if (direction)
+                stat[BLKIO_STAT_WRITE] += add;
         else
-                stat[IO_READ] += add;
-        /*
-         * Everywhere in the block layer, an IO is treated as sync if it is a
-         * read or a SYNC write. We follow the same norm.
-         */
-        if (!(flags & REQ_RW) || flags & REQ_RW_SYNC)
-                stat[IO_SYNC] += add;
+                stat[BLKIO_STAT_READ] += add;
+        if (sync)
+                stat[BLKIO_STAT_SYNC] += add;
         else
-                stat[IO_ASYNC] += add;
+                stat[BLKIO_STAT_ASYNC] += add;
 }
 
 void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time)
@@ -86,23 +91,25 @@ void blkiocg_update_timeslice_used(struct blkio_group *blkg, unsigned long time)
 }
 EXPORT_SYMBOL_GPL(blkiocg_update_timeslice_used);
 
-void blkiocg_update_request_dispatch_stats(struct blkio_group *blkg,
-                                                struct request *rq)
+void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
+                                uint64_t bytes, bool direction, bool sync)
 {
         struct blkio_group_stats *stats;
         unsigned long flags;
 
         spin_lock_irqsave(&blkg->stats_lock, flags);
         stats = &blkg->stats;
-        stats->sectors += blk_rq_sectors(rq);
-        io_add_stat(stats->io_serviced, 1, rq->cmd_flags);
-        io_add_stat(stats->io_service_bytes, blk_rq_sectors(rq) << 9,
-                        rq->cmd_flags);
+        stats->sectors += bytes >> 9;
+        blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICED], 1, direction,
+                        sync);
+        blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICE_BYTES], bytes,
+                        direction, sync);
         spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
+EXPORT_SYMBOL_GPL(blkiocg_update_dispatch_stats);
 
-void blkiocg_update_request_completion_stats(struct blkio_group *blkg,
-                                                struct request *rq)
+void blkiocg_update_completion_stats(struct blkio_group *blkg,
+        uint64_t start_time, uint64_t io_start_time, bool direction, bool sync)
 {
         struct blkio_group_stats *stats;
         unsigned long flags;
@@ -110,16 +117,15 @@ void blkiocg_update_request_completion_stats(struct blkio_group *blkg,
 
         spin_lock_irqsave(&blkg->stats_lock, flags);
         stats = &blkg->stats;
-        if (time_after64(now, rq->io_start_time_ns))
-                io_add_stat(stats->io_service_time, now - rq->io_start_time_ns,
-                                rq->cmd_flags);
-        if (time_after64(rq->io_start_time_ns, rq->start_time_ns))
-                io_add_stat(stats->io_wait_time,
-                                rq->io_start_time_ns - rq->start_time_ns,
-                                rq->cmd_flags);
+        if (time_after64(now, io_start_time))
+                blkio_add_stat(stats->stat_arr[BLKIO_STAT_SERVICE_TIME],
+                                now - io_start_time, direction, sync);
+        if (time_after64(io_start_time, start_time))
+                blkio_add_stat(stats->stat_arr[BLKIO_STAT_WAIT_TIME],
+                                io_start_time - start_time, direction, sync);
         spin_unlock_irqrestore(&blkg->stats_lock, flags);
 }
-EXPORT_SYMBOL_GPL(blkiocg_update_request_completion_stats);
+EXPORT_SYMBOL_GPL(blkiocg_update_completion_stats);
 
 void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
                         struct blkio_group *blkg, void *key, dev_t dev)
@@ -230,7 +236,7 @@ blkiocg_weight_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 }
 
 static int
-blkiocg_reset_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
+blkiocg_reset_stats(struct cgroup *cgroup, struct cftype *cftype, u64 val)
 {
         struct blkio_cgroup *blkcg;
         struct blkio_group *blkg;
@@ -249,29 +255,32 @@ blkiocg_reset_write(struct cgroup *cgroup, struct cftype *cftype, u64 val)
         return 0;
 }
 
-void get_key_name(int type, char *disk_id, char *str, int chars_left)
+static void blkio_get_key_name(enum stat_sub_type type, dev_t dev, char *str,
+                                int chars_left, bool diskname_only)
 {
-        strlcpy(str, disk_id, chars_left);
+        snprintf(str, chars_left, "%d:%d", MAJOR(dev), MINOR(dev));
         chars_left -= strlen(str);
         if (chars_left <= 0) {
                 printk(KERN_WARNING
                         "Possibly incorrect cgroup stat display format");
                 return;
         }
+        if (diskname_only)
+                return;
         switch (type) {
-        case IO_READ:
+        case BLKIO_STAT_READ:
                 strlcat(str, " Read", chars_left);
                 break;
-        case IO_WRITE:
+        case BLKIO_STAT_WRITE:
                 strlcat(str, " Write", chars_left);
                 break;
-        case IO_SYNC:
+        case BLKIO_STAT_SYNC:
                 strlcat(str, " Sync", chars_left);
                 break;
-        case IO_ASYNC:
+        case BLKIO_STAT_ASYNC:
                 strlcat(str, " Async", chars_left);
                 break;
-        case IO_TYPE_MAX:
+        case BLKIO_STAT_TOTAL:
                 strlcat(str, " Total", chars_left);
                 break;
         default:
@@ -279,63 +288,47 @@ void get_key_name(int type, char *disk_id, char *str, int chars_left)
         }
 }
 
-typedef uint64_t (get_var) (struct blkio_group *, int);
+static uint64_t blkio_fill_stat(char *str, int chars_left, uint64_t val,
+                                struct cgroup_map_cb *cb, dev_t dev)
+{
+        blkio_get_key_name(0, dev, str, chars_left, true);
+        cb->fill(cb, str, val);
+        return val;
+}
 
-#define MAX_KEY_LEN 100
-uint64_t get_typed_stat(struct blkio_group *blkg, struct cgroup_map_cb *cb,
-                get_var *getvar, char *disk_id)
+/* This should be called with blkg->stats_lock held */
+static uint64_t blkio_get_stat(struct blkio_group *blkg,
+                struct cgroup_map_cb *cb, dev_t dev, enum stat_type type)
 {
         uint64_t disk_total;
         char key_str[MAX_KEY_LEN];
-        int type;
+        enum stat_sub_type sub_type;
+
+        if (type == BLKIO_STAT_TIME)
+                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+                                        blkg->stats.time, cb, dev);
+        if (type == BLKIO_STAT_SECTORS)
+                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+                                        blkg->stats.sectors, cb, dev);
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+        if (type == BLKIO_STAT_DEQUEUE)
+                return blkio_fill_stat(key_str, MAX_KEY_LEN - 1,
+                                        blkg->stats.dequeue, cb, dev);
+#endif
 
-        for (type = 0; type < IO_TYPE_MAX; type++) {
-                get_key_name(type, disk_id, key_str, MAX_KEY_LEN);
-                cb->fill(cb, key_str, getvar(blkg, type));
+        for (sub_type = BLKIO_STAT_READ; sub_type < BLKIO_STAT_TOTAL;
+                        sub_type++) {
+                blkio_get_key_name(sub_type, dev, key_str, MAX_KEY_LEN, false);
+                cb->fill(cb, key_str, blkg->stats.stat_arr[type][sub_type]);
         }
-        disk_total = getvar(blkg, IO_READ) + getvar(blkg, IO_WRITE);
-        get_key_name(IO_TYPE_MAX, disk_id, key_str, MAX_KEY_LEN);
+        disk_total = blkg->stats.stat_arr[type][BLKIO_STAT_READ] +
+                        blkg->stats.stat_arr[type][BLKIO_STAT_WRITE];
+        blkio_get_key_name(BLKIO_STAT_TOTAL, dev, key_str, MAX_KEY_LEN, false);
         cb->fill(cb, key_str, disk_total);
         return disk_total;
 }
 
-uint64_t get_stat(struct blkio_group *blkg, struct cgroup_map_cb *cb,
-                get_var *getvar, char *disk_id)
-{
-        uint64_t var = getvar(blkg, 0);
-        cb->fill(cb, disk_id, var);
-        return var;
-}
-
-#define GET_STAT_INDEXED(__VAR)                                         \
-uint64_t get_##__VAR##_stat(struct blkio_group *blkg, int type)         \
-{                                                                       \
-        return blkg->stats.__VAR[type];                                 \
-}                                                                       \
-
-GET_STAT_INDEXED(io_service_bytes);
-GET_STAT_INDEXED(io_serviced);
-GET_STAT_INDEXED(io_service_time);
-GET_STAT_INDEXED(io_wait_time);
-#undef GET_STAT_INDEXED
-
-#define GET_STAT(__VAR, __CONV)                                         \
-uint64_t get_##__VAR##_stat(struct blkio_group *blkg, int dummy)        \
-{                                                                       \
-        uint64_t data = blkg->stats.__VAR;                              \
-        if (__CONV)                                                     \
-                data = (uint64_t)jiffies_to_msecs(data) * NSEC_PER_MSEC;\
-        return data;                                                    \
-}
-
-GET_STAT(time, 1);
-GET_STAT(sectors, 0);
-#ifdef CONFIG_DEBUG_BLK_CGROUP
-GET_STAT(dequeue, 0);
-#endif
-#undef GET_STAT
-
-#define SHOW_FUNCTION_PER_GROUP(__VAR, get_stats, getvar, show_total)   \
+#define SHOW_FUNCTION_PER_GROUP(__VAR, type, show_total)                \
 static int blkiocg_##__VAR##_read(struct cgroup *cgroup,                \
                 struct cftype *cftype, struct cgroup_map_cb *cb)        \
 {                                                                       \
@@ -343,7 +336,6 @@ static int blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
         struct blkio_group *blkg;                                       \
         struct hlist_node *n;                                           \
         uint64_t cgroup_total = 0;                                      \
-        char disk_id[10];                                               \
                                                                         \
         if (!cgroup_lock_live_group(cgroup))                            \
                 return -ENODEV;                                         \
@@ -353,10 +345,8 @@ static int blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
         hlist_for_each_entry_rcu(blkg, n, &blkcg->blkg_list, blkcg_node) {\
                 if (blkg->dev) {                                        \
                         spin_lock_irq(&blkg->stats_lock);               \
-                        snprintf(disk_id, 10, "%u:%u", MAJOR(blkg->dev),\
-                                        MINOR(blkg->dev));              \
-                        cgroup_total += get_stats(blkg, cb, getvar,     \
-                                                disk_id);               \
+                        cgroup_total += blkio_get_stat(blkg, cb,        \
+                                                blkg->dev, type);       \
                         spin_unlock_irq(&blkg->stats_lock);             \
                 }                                                       \
         }                                                               \
@@ -367,16 +357,14 @@ static int blkiocg_##__VAR##_read(struct cgroup *cgroup,		\
         return 0;                                                       \
 }
 
-SHOW_FUNCTION_PER_GROUP(time, get_stat, get_time_stat, 0);
-SHOW_FUNCTION_PER_GROUP(sectors, get_stat, get_sectors_stat, 0);
-SHOW_FUNCTION_PER_GROUP(io_service_bytes, get_typed_stat,
-                        get_io_service_bytes_stat, 1);
-SHOW_FUNCTION_PER_GROUP(io_serviced, get_typed_stat, get_io_serviced_stat, 1);
-SHOW_FUNCTION_PER_GROUP(io_service_time, get_typed_stat,
-                        get_io_service_time_stat, 1);
-SHOW_FUNCTION_PER_GROUP(io_wait_time, get_typed_stat, get_io_wait_time_stat, 1);
+SHOW_FUNCTION_PER_GROUP(time, BLKIO_STAT_TIME, 0);
+SHOW_FUNCTION_PER_GROUP(sectors, BLKIO_STAT_SECTORS, 0);
+SHOW_FUNCTION_PER_GROUP(io_service_bytes, BLKIO_STAT_SERVICE_BYTES, 1);
+SHOW_FUNCTION_PER_GROUP(io_serviced, BLKIO_STAT_SERVICED, 1);
+SHOW_FUNCTION_PER_GROUP(io_service_time, BLKIO_STAT_SERVICE_TIME, 1);
+SHOW_FUNCTION_PER_GROUP(io_wait_time, BLKIO_STAT_WAIT_TIME, 1);
 #ifdef CONFIG_DEBUG_BLK_CGROUP
-SHOW_FUNCTION_PER_GROUP(dequeue, get_stat, get_dequeue_stat, 0);
+SHOW_FUNCTION_PER_GROUP(dequeue, BLKIO_STAT_DEQUEUE, 0);
 #endif
 #undef SHOW_FUNCTION_PER_GROUP
 
@@ -398,32 +386,30 @@ struct cftype blkio_files[] = {
         {
                 .name = "time",
                 .read_map = blkiocg_time_read,
-                .write_u64 = blkiocg_reset_write,
         },
         {
                 .name = "sectors",
                 .read_map = blkiocg_sectors_read,
-                .write_u64 = blkiocg_reset_write,
         },
         {
                 .name = "io_service_bytes",
                 .read_map = blkiocg_io_service_bytes_read,
-                .write_u64 = blkiocg_reset_write,
         },
         {
                 .name = "io_serviced",
                 .read_map = blkiocg_io_serviced_read,
-                .write_u64 = blkiocg_reset_write,
         },
         {
                 .name = "io_service_time",
                 .read_map = blkiocg_io_service_time_read,
-                .write_u64 = blkiocg_reset_write,
         },
         {
                 .name = "io_wait_time",
                 .read_map = blkiocg_io_wait_time_read,
-                .write_u64 = blkiocg_reset_write,
+        },
+        {
+                .name = "reset_stats",
+                .write_u64 = blkiocg_reset_stats,
         },
 #ifdef CONFIG_DEBUG_BLK_CGROUP
        {
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h
index 80010ef64ab0..b22e55390a4f 100644
--- a/block/blk-cgroup.h
+++ b/block/blk-cgroup.h
@@ -23,12 +23,31 @@ extern struct cgroup_subsys blkio_subsys;
 #define blkio_subsys_id blkio_subsys.subsys_id
 #endif
 
-enum io_type {
-        IO_READ = 0,
-        IO_WRITE,
-        IO_SYNC,
-        IO_ASYNC,
-        IO_TYPE_MAX
+enum stat_type {
+        /* Total time spent (in ns) between request dispatch to the driver and
+         * request completion for IOs doen by this cgroup. This may not be
+         * accurate when NCQ is turned on. */
+        BLKIO_STAT_SERVICE_TIME = 0,
+        /* Total bytes transferred */
+        BLKIO_STAT_SERVICE_BYTES,
+        /* Total IOs serviced, post merge */
+        BLKIO_STAT_SERVICED,
+        /* Total time spent waiting in scheduler queue in ns */
+        BLKIO_STAT_WAIT_TIME,
+        /* All the single valued stats go below this */
+        BLKIO_STAT_TIME,
+        BLKIO_STAT_SECTORS,
+#ifdef CONFIG_DEBUG_BLK_CGROUP
+        BLKIO_STAT_DEQUEUE
+#endif
+};
+
+enum stat_sub_type {
+        BLKIO_STAT_READ = 0,
+        BLKIO_STAT_WRITE,
+        BLKIO_STAT_SYNC,
+        BLKIO_STAT_ASYNC,
+        BLKIO_STAT_TOTAL
 };
 
 struct blkio_cgroup {
@@ -42,13 +61,7 @@ struct blkio_group_stats {
         /* total disk time and nr sectors dispatched by this group */
         uint64_t time;
         uint64_t sectors;
-        /* Total disk time used by IOs in ns */
-        uint64_t io_service_time[IO_TYPE_MAX];
-        uint64_t io_service_bytes[IO_TYPE_MAX]; /* Total bytes transferred */
-        /* Total IOs serviced, post merge */
-        uint64_t io_serviced[IO_TYPE_MAX];
-        /* Total time spent waiting in scheduler queue in ns */
-        uint64_t io_wait_time[IO_TYPE_MAX];
+        uint64_t stat_arr[BLKIO_STAT_WAIT_TIME + 1][BLKIO_STAT_TOTAL];
 #ifdef CONFIG_DEBUG_BLK_CGROUP
         /* How many times this group has been removed from service tree */
         unsigned long dequeue;
@@ -65,7 +78,7 @@ struct blkio_group {
         char path[128];
 #endif
         /* The device MKDEV(major, minor), this group has been created for */
-        dev_t   dev;
+        dev_t dev;
 
         /* Need to serialize the stats in the case of reset/update */
         spinlock_t stats_lock;
@@ -128,21 +141,21 @@ extern void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
 extern int blkiocg_del_blkio_group(struct blkio_group *blkg);
 extern struct blkio_group *blkiocg_lookup_group(struct blkio_cgroup *blkcg,
                                                 void *key);
+void blkio_group_init(struct blkio_group *blkg);
 void blkiocg_update_timeslice_used(struct blkio_group *blkg,
                                         unsigned long time);
-void blkiocg_update_request_dispatch_stats(struct blkio_group *blkg,
-                                                struct request *rq);
-void blkiocg_update_request_completion_stats(struct blkio_group *blkg,
-                                                struct request *rq);
+void blkiocg_update_dispatch_stats(struct blkio_group *blkg, uint64_t bytes,
+                                                bool direction, bool sync);
+void blkiocg_update_completion_stats(struct blkio_group *blkg,
+        uint64_t start_time, uint64_t io_start_time, bool direction, bool sync);
 #else
 struct cgroup;
 static inline struct blkio_cgroup *
 cgroup_to_blkio_cgroup(struct cgroup *cgroup) { return NULL; }
 
+static inline void blkio_group_init(struct blkio_group *blkg) {}
 static inline void blkiocg_add_blkio_group(struct blkio_cgroup *blkcg,
-                        struct blkio_group *blkg, void *key, dev_t dev)
-{
-}
+                        struct blkio_group *blkg, void *key, dev_t dev) {}
 
 static inline int
 blkiocg_del_blkio_group(struct blkio_group *blkg) { return 0; }
@@ -151,9 +164,10 @@ static inline struct blkio_group *
 blkiocg_lookup_group(struct blkio_cgroup *blkcg, void *key) { return NULL; }
 static inline void blkiocg_update_timeslice_used(struct blkio_group *blkg,
                                                 unsigned long time) {}
-static inline void blkiocg_update_request_dispatch_stats(
-                struct blkio_group *blkg, struct request *rq) {}
-static inline void blkiocg_update_request_completion_stats(
-                struct blkio_group *blkg, struct request *rq) {}
+static inline void blkiocg_update_dispatch_stats(struct blkio_group *blkg,
+                                uint64_t bytes, bool direction, bool sync) {}
+static inline void blkiocg_update_completion_stats(struct blkio_group *blkg,
+                uint64_t start_time, uint64_t io_start_time, bool direction,
+                bool sync) {}
 #endif
 #endif /* _BLK_CGROUP_H */
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index 42028e7128a7..5617ae030b15 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -955,6 +955,7 @@ cfq_find_alloc_cfqg(struct cfq_data *cfqd, struct cgroup *cgroup, int create)
         for_each_cfqg_st(cfqg, i, j, st)
                 *st = CFQ_RB_ROOT;
         RB_CLEAR_NODE(&cfqg->rb_node);
+        blkio_group_init(&cfqg->blkg);
 
         /*
          * Take the initial reference that will be released on destroy
@@ -1865,7 +1866,8 @@ static void cfq_dispatch_insert(struct request_queue *q, struct request *rq)
         elv_dispatch_sort(q, rq);
 
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]++;
-        blkiocg_update_request_dispatch_stats(&cfqq->cfqg->blkg, rq);
+        blkiocg_update_dispatch_stats(&cfqq->cfqg->blkg, blk_rq_bytes(rq),
+                                        rq_data_dir(rq), rq_is_sync(rq));
 }
 
 /*
@@ -3286,7 +3288,9 @@ static void cfq_completed_request(struct request_queue *q, struct request *rq)
         WARN_ON(!cfqq->dispatched);
         cfqd->rq_in_driver--;
         cfqq->dispatched--;
-        blkiocg_update_request_completion_stats(&cfqq->cfqg->blkg, rq);
+        blkiocg_update_completion_stats(&cfqq->cfqg->blkg, rq_start_time_ns(rq),
+                        rq_io_start_time_ns(rq), rq_data_dir(rq),
+                        rq_is_sync(rq));
 
         cfqd->rq_in_flight[cfq_cfqq_sync(cfqq)]--;