block/blk-stat.h

   1 #ifndef BLK_STAT_H
   2 #define BLK_STAT_H
   3
   4 #include <linux/kernel.h>
   5 #include <linux/blkdev.h>
   6 #include <linux/ktime.h>
   7 #include <linux/rcupdate.h>
   8 #include <linux/timer.h>
   9
  10 /*
  11  * from upper:
  12  * 3 bits: reserved for other usage
  13  * 12 bits: size
  14  * 49 bits: time
  15  */
  16 #define BLK_STAT_RES_BITS       3
  17 #define BLK_STAT_SIZE_BITS      12
  18 #define BLK_STAT_RES_SHIFT      (64 - BLK_STAT_RES_BITS)
  19 #define BLK_STAT_SIZE_SHIFT     (BLK_STAT_RES_SHIFT - BLK_STAT_SIZE_BITS)
  20 #define BLK_STAT_TIME_MASK      ((1ULL << BLK_STAT_SIZE_SHIFT) - 1)
  21 #define BLK_STAT_SIZE_MASK      \
  22         (((1ULL << BLK_STAT_SIZE_BITS) - 1) << BLK_STAT_SIZE_SHIFT)
  23 #define BLK_STAT_RES_MASK       (~((1ULL << BLK_STAT_RES_SHIFT) - 1))
  24
  25 /**
  26  * struct blk_stat_callback - Block statistics callback.
  27  *
  28  * A &struct blk_stat_callback is associated with a &struct request_queue. While
  29  * @timer is active, that queue's request completion latencies are sorted into
  30  * buckets by @bucket_fn and added to a per-cpu buffer, @cpu_stat. When the
  31  * timer fires, @cpu_stat is flushed to @stat and @timer_fn is invoked.
  32  */
  33 struct blk_stat_callback {
  34         /*
  35          * @list: RCU list of callbacks for a &struct request_queue.
  36          */
  37         struct list_head list;
  38
  39         /**
  40          * @timer: Timer for the next callback invocation.
  41          */
  42         struct timer_list timer;
  43
  44         /**
  45          * @cpu_stat: Per-cpu statistics buckets.
  46          */
  47         struct blk_rq_stat __percpu *cpu_stat;
  48
  49         /**
  50          * @bucket_fn: Given a request, returns which statistics bucket it
  51          * should be accounted under. Return -1 for no bucket for this
  52          * request.
  53          */
  54         int (*bucket_fn)(const struct request *);
  55
  56         /**
  57          * @buckets: Number of statistics buckets.
  58          */
  59         unsigned int buckets;
  60
  61         /**
  62          * @stat: Array of statistics buckets.
  63          */
  64         struct blk_rq_stat *stat;
  65
  66         /**
  67          * @fn: Callback function.
  68          */
  69         void (*timer_fn)(struct blk_stat_callback *);
  70
  71         /**
  72          * @data: Private pointer for the user.
  73          */
  74         void *data;
  75
  76         struct rcu_head rcu;
  77 };
  78
  79 struct blk_queue_stats *blk_alloc_queue_stats(void);
  80 void blk_free_queue_stats(struct blk_queue_stats *);
  81
  82 void blk_stat_add(struct request *);
  83
  84 static inline u64 __blk_stat_time(u64 time)
  85 {
  86         return time & BLK_STAT_TIME_MASK;
  87 }
  88
  89 static inline u64 blk_stat_time(struct blk_issue_stat *stat)
  90 {
  91         return __blk_stat_time(stat->stat);
  92 }
  93
  94 static inline sector_t blk_capped_size(sector_t size)
  95 {
  96         return size & ((1ULL << BLK_STAT_SIZE_BITS) - 1);
  97 }
  98
  99 static inline sector_t blk_stat_size(struct blk_issue_stat *stat)
 100 {
 101         return (stat->stat & BLK_STAT_SIZE_MASK) >> BLK_STAT_SIZE_SHIFT;
 102 }
 103
 104 static inline void blk_stat_set_issue(struct blk_issue_stat *stat,
 105         sector_t size)
 106 {
 107         stat->stat = (stat->stat & BLK_STAT_RES_MASK) |
 108                 (ktime_to_ns(ktime_get()) & BLK_STAT_TIME_MASK) |
 109                 (((u64)blk_capped_size(size)) << BLK_STAT_SIZE_SHIFT);
 110 }
 111
 112 /* record time/size info in request but not add a callback */
 113 void blk_stat_enable_accounting(struct request_queue *q);
 114
 115 /**
 116  * blk_stat_alloc_callback() - Allocate a block statistics callback.
 117  * @timer_fn: Timer callback function.
 118  * @bucket_fn: Bucket callback function.
 119  * @buckets: Number of statistics buckets.
 120  * @data: Value for the @data field of the &struct blk_stat_callback.
 121  *
 122  * See &struct blk_stat_callback for details on the callback functions.
 123  *
 124  * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
 125  */
 126 struct blk_stat_callback *
 127 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
 128                         int (*bucket_fn)(const struct request *),
 129                         unsigned int buckets, void *data);
 130
 131 /**
 132  * blk_stat_add_callback() - Add a block statistics callback to be run on a
 133  * request queue.
 134  * @q: The request queue.
 135  * @cb: The callback.
 136  *
 137  * Note that a single &struct blk_stat_callback can only be added to a single
 138  * &struct request_queue.
 139  */
 140 void blk_stat_add_callback(struct request_queue *q,
 141                            struct blk_stat_callback *cb);
 142
 143 /**
 144  * blk_stat_remove_callback() - Remove a block statistics callback from a
 145  * request queue.
 146  * @q: The request queue.
 147  * @cb: The callback.
 148  *
 149  * When this returns, the callback is not running on any CPUs and will not be
 150  * called again unless readded.
 151  */
 152 void blk_stat_remove_callback(struct request_queue *q,
 153                               struct blk_stat_callback *cb);
 154
 155 /**
 156  * blk_stat_free_callback() - Free a block statistics callback.
 157  * @cb: The callback.
 158  *
 159  * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
 160  * not be associated with a request queue. I.e., if it was previously added with
 161  * blk_stat_add_callback(), it must also have been removed since then with
 162  * blk_stat_remove_callback().
 163  */
 164 void blk_stat_free_callback(struct blk_stat_callback *cb);
 165
 166 /**
 167  * blk_stat_is_active() - Check if a block statistics callback is currently
 168  * gathering statistics.
 169  * @cb: The callback.
 170  */
 171 static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
 172 {
 173         return timer_pending(&cb->timer);
 174 }
 175
 176 /**
 177  * blk_stat_activate_nsecs() - Gather block statistics during a time window in
 178  * nanoseconds.
 179  * @cb: The callback.
 180  * @nsecs: Number of nanoseconds to gather statistics for.
 181  *
 182  * The timer callback will be called when the window expires.
 183  */
 184 static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
 185                                            u64 nsecs)
 186 {
 187         mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
 188 }
 189
 190 /**
 191  * blk_stat_activate_msecs() - Gather block statistics during a time window in
 192  * milliseconds.
 193  * @cb: The callback.
 194  * @msecs: Number of milliseconds to gather statistics for.
 195  *
 196  * The timer callback will be called when the window expires.
 197  */
 198 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
 199                                            unsigned int msecs)
 200 {
 201         mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
 202 }
 203
 204 #endif