the-tree/block/blk-stat.h

0001 /* SPDX-License-Identifier: GPL-2.0 */
0002 #ifndef BLK_STAT_H
0003 #define BLK_STAT_H
0004
0005 #include <linux/kernel.h>
0006 #include <linux/blkdev.h>
0007 #include <linux/ktime.h>
0008 #include <linux/rcupdate.h>
0009 #include <linux/timer.h>
0010
0011 /**
0012  * struct blk_stat_callback - Block statistics callback.
0013  *
0014  * A &struct blk_stat_callback is associated with a &struct request_queue. While
0015  * @timer is active, that queue's request completion latencies are sorted into
0016  * buckets by @bucket_fn and added to a per-cpu buffer, @cpu_stat. When the
0017  * timer fires, @cpu_stat is flushed to @stat and @timer_fn is invoked.
0018  */
0019 struct blk_stat_callback {
0020     /*
0021      * @list: RCU list of callbacks for a &struct request_queue.
0022      */
0023     struct list_head list;
0024
0025     /**
0026      * @timer: Timer for the next callback invocation.
0027      */
0028     struct timer_list timer;
0029
0030     /**
0031      * @cpu_stat: Per-cpu statistics buckets.
0032      */
0033     struct blk_rq_stat __percpu *cpu_stat;
0034
0035     /**
0036      * @bucket_fn: Given a request, returns which statistics bucket it
0037      * should be accounted under. Return -1 for no bucket for this
0038      * request.
0039      */
0040     int (*bucket_fn)(const struct request *);
0041
0042     /**
0043      * @buckets: Number of statistics buckets.
0044      */
0045     unsigned int buckets;
0046
0047     /**
0048      * @stat: Array of statistics buckets.
0049      */
0050     struct blk_rq_stat *stat;
0051
0052     /**
0053      * @fn: Callback function.
0054      */
0055     void (*timer_fn)(struct blk_stat_callback *);
0056
0057     /**
0058      * @data: Private pointer for the user.
0059      */
0060     void *data;
0061
0062     struct rcu_head rcu;
0063 };
0064
0065 struct blk_queue_stats *blk_alloc_queue_stats(void);
0066 void blk_free_queue_stats(struct blk_queue_stats *);
0067 bool blk_stats_alloc_enable(struct request_queue *q);
0068
0069 void blk_stat_add(struct request *rq, u64 now);
0070
0071 /* record time/size info in request but not add a callback */
0072 void blk_stat_enable_accounting(struct request_queue *q);
0073 void blk_stat_disable_accounting(struct request_queue *q);
0074
0075 /**
0076  * blk_stat_alloc_callback() - Allocate a block statistics callback.
0077  * @timer_fn: Timer callback function.
0078  * @bucket_fn: Bucket callback function.
0079  * @buckets: Number of statistics buckets.
0080  * @data: Value for the @data field of the &struct blk_stat_callback.
0081  *
0082  * See &struct blk_stat_callback for details on the callback functions.
0083  *
0084  * Return: &struct blk_stat_callback on success or NULL on ENOMEM.
0085  */
0086 struct blk_stat_callback *
0087 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
0088             int (*bucket_fn)(const struct request *),
0089             unsigned int buckets, void *data);
0090
0091 /**
0092  * blk_stat_add_callback() - Add a block statistics callback to be run on a
0093  * request queue.
0094  * @q: The request queue.
0095  * @cb: The callback.
0096  *
0097  * Note that a single &struct blk_stat_callback can only be added to a single
0098  * &struct request_queue.
0099  */
0100 void blk_stat_add_callback(struct request_queue *q,
0101                struct blk_stat_callback *cb);
0102
0103 /**
0104  * blk_stat_remove_callback() - Remove a block statistics callback from a
0105  * request queue.
0106  * @q: The request queue.
0107  * @cb: The callback.
0108  *
0109  * When this returns, the callback is not running on any CPUs and will not be
0110  * called again unless readded.
0111  */
0112 void blk_stat_remove_callback(struct request_queue *q,
0113                   struct blk_stat_callback *cb);
0114
0115 /**
0116  * blk_stat_free_callback() - Free a block statistics callback.
0117  * @cb: The callback.
0118  *
0119  * @cb may be NULL, in which case this does nothing. If it is not NULL, @cb must
0120  * not be associated with a request queue. I.e., if it was previously added with
0121  * blk_stat_add_callback(), it must also have been removed since then with
0122  * blk_stat_remove_callback().
0123  */
0124 void blk_stat_free_callback(struct blk_stat_callback *cb);
0125
0126 /**
0127  * blk_stat_is_active() - Check if a block statistics callback is currently
0128  * gathering statistics.
0129  * @cb: The callback.
0130  */
0131 static inline bool blk_stat_is_active(struct blk_stat_callback *cb)
0132 {
0133     return timer_pending(&cb->timer);
0134 }
0135
0136 /**
0137  * blk_stat_activate_nsecs() - Gather block statistics during a time window in
0138  * nanoseconds.
0139  * @cb: The callback.
0140  * @nsecs: Number of nanoseconds to gather statistics for.
0141  *
0142  * The timer callback will be called when the window expires.
0143  */
0144 static inline void blk_stat_activate_nsecs(struct blk_stat_callback *cb,
0145                        u64 nsecs)
0146 {
0147     mod_timer(&cb->timer, jiffies + nsecs_to_jiffies(nsecs));
0148 }
0149
0150 static inline void blk_stat_deactivate(struct blk_stat_callback *cb)
0151 {
0152     del_timer_sync(&cb->timer);
0153 }
0154
0155 /**
0156  * blk_stat_activate_msecs() - Gather block statistics during a time window in
0157  * milliseconds.
0158  * @cb: The callback.
0159  * @msecs: Number of milliseconds to gather statistics for.
0160  *
0161  * The timer callback will be called when the window expires.
0162  */
0163 static inline void blk_stat_activate_msecs(struct blk_stat_callback *cb,
0164                        unsigned int msecs)
0165 {
0166     mod_timer(&cb->timer, jiffies + msecs_to_jiffies(msecs));
0167 }
0168
0169 void blk_rq_stat_add(struct blk_rq_stat *, u64);
0170 void blk_rq_stat_sum(struct blk_rq_stat *, struct blk_rq_stat *);
0171 void blk_rq_stat_init(struct blk_rq_stat *);
0172
0173 #endif