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TOMOYO Linux Cross Reference
Linux/block/blk-stat.h

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  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
205 

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