block/blk-stat.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef BLK_STAT_H
   3 #define BLK_STAT_H
   4
   5 #include <linux/kernel.h>
   6 #include <linux/blkdev.h>
   7 #include <linux/ktime.h>
   8 #include <linux/rcupdate.h>
   9 #include <linux/timer.h>
  10
  11 /**
  12  * struct blk_stat_callback - Block statistics callback.
  13  *
  14  * A &struct blk_stat_callback is associated with a &struct request_queue. While
  15  * @timer is active, that queue's request completion latencies are sorted into
  16  * buckets by @bucket_fn and added to a per-cpu buffer, @cpu_stat. When the
  17  * timer fires, @cpu_stat is flushed to @stat and @timer_fn is invoked.
  18  */
  19 struct blk_stat_callback {
  20         /*
  21          * @list: RCU list of callbacks for a &struct request_queue.
  22          */
  23         struct list_head list;
  24
  25         /**
  26          * @timer: Timer for the next callback invocation.
  27          */
  28         struct timer_list timer;
  29
  30         /**
  31          * @cpu_stat: Per-cpu statistics buckets.
  32          */
  33         struct blk_rq_stat __percpu *cpu_stat;
  34
  35         /**
  36          * @bucket_fn: Given a request, returns which statistics bucket it
  37          * should be accounted under. Return -1 for no bucket for this
  38          * request.
  39          */
  40         int (*bucket_fn)(const struct request *);
  41
  42         /**
  43          * @buckets: Number of statistics buckets.
  44          */
  45         unsigned int buckets;
  46
  47         /**
  48          * @stat: Array of statistics buckets.
  49          */
  50         struct blk_rq_stat *stat;
  51
  52         /**
  53          * @fn: Callback function.
  54          */
  55         void (*timer_fn)(struct blk_stat_callback *);
  56
  57         /**
  58          * @data: Private pointer for the user.
  59          */
  60         void *data;
  61
  62         struct rcu_head rcu;
  63 };
  64
  65 struct blk_queue_stats *blk_alloc_queue_stats(void);
  66 void blk_free_queue_stats(struct blk_queue_stats *);
  67
  68 void blk_stat_add(struct request *rq, u64 now);
  69
  70 /* record time/size info in request but not add a callback */
  71 void blk_stat_enable_accounting(struct request_queue *q);
  72
  73 /**
  74  * blk_stat_alloc_callback() - Allocate a block statistics callback.
  75  * @timer_fn: Timer callback function.
  76  * @bucket_fn: Bucket callback function.
  77  * @buckets: Number of statistics buckets.
  78  * @data: Value for the @data field of the &struct blk_stat_callback.
  79  *
  80  * See &struct blk_stat_callback for details on the callback functions.
  81  *
  82  * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
  83  */
  84 struct blk_stat_callback *
  85 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
  86                         int (*bucket_fn)(const struct request *),
  87                         unsigned int buckets, void *data);
  88
  89 /**
  90  * blk_stat_add_callback() - Add a block statistics callback to be run on a
  91  * request queue.
  92  * @q: The request queue.
  93  * @cb: The callback.
  94  *
  95  * Note that a single &struct blk_stat_callback can only be added to a single
  96  * &struct request_queue.
  97  */
  98 void blk_stat_add_callback(struct request_queue *q,
  99                            struct blk_stat_callback *cb);
 100
 101 /**
 102  * blk_stat_remove_callback() - Remove a block statistics callback from a
 103  * request queue.
 104  * @q: The request queue.
 105  * @cb: The callback.
 106  *
 107  * When this returns, the callback is not running on any CPUs and will not be
 108  * called again unless readded.
 109  */
 110 void blk_stat_remove_callback(struct request_queue *q,
 111                               struct blk_stat_callback *cb);
 112
 113 /**
 114  * blk_stat_free_callback() - Free a block statistics callback.
 115  * @cb: The callback.
 116  *
 117  * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
 118  * not be associated with a request queue. I.e., if it was previously added with
 119  * blk_stat_add_callback(), it must also have been removed since then with
 120  * blk_stat_remove_callback().
 121  */
 122 void blk_stat_free_callback(struct blk_stat_callback *cb);
 123
 124 /**
 125  * blk_stat_is_active() - Check if a block statistics callback is currently
 126  * gathering statistics.
 127  * @cb: The callback.
 128  */
 129 static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
 130 {
 131         return timer_pending(&cb->timer);
 132 }
 133
 134 /**
 135  * blk_stat_activate_nsecs() - Gather block statistics during a time window in
 136  * nanoseconds.
 137  * @cb: The callback.
 138  * @nsecs: Number of nanoseconds to gather statistics for.
 139  *
 140  * The timer callback will be called when the window expires.
 141  */
 142 static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
 143                                            u64 nsecs)
 144 {
 145         mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
 146 }
 147
 148 /**
 149  * blk_stat_activate_msecs() - Gather block statistics during a time window in
 150  * milliseconds.
 151  * @cb: The callback.
 152  * @msecs: Number of milliseconds to gather statistics for.
 153  *
 154  * The timer callback will be called when the window expires.
 155  */
 156 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
 157                                            unsigned int msecs)
 158 {
 159         mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
 160 }
 161
 162 void blk_rq_stat_add(struct blk_rq_stat *, u64);
 163 void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *);
 164 void blk_rq_stat_init(struct blk_rq_stat *);
 165
 166 #endif