1 /*
2  * Block stat tracking code
3  *
4  * Copyright (C) 2016 Jens Axboe
5  */
6 #include <linux/kernel.h>
7 #include <linux/rculist.h>
8 #include <linux/blk-mq.h>
9 
10 #include "blk-stat.h"
11 #include "blk-mq.h"
12 #include "blk.h"
13 
14 struct blk_queue_stats {
15 	struct list_head callbacks;
16 	spinlock_t lock;
17 	bool enable_accounting;
18 };
19 
blk_rq_stat_init(struct blk_rq_stat * stat)20 void blk_rq_stat_init(struct blk_rq_stat *stat)
21 {
22 	stat->min = -1ULL;
23 	stat->max = stat->nr_samples = stat->mean = 0;
24 	stat->batch = 0;
25 }
26 
27 /* src is a per-cpu stat, mean isn't initialized */
blk_rq_stat_sum(struct blk_rq_stat * dst,struct blk_rq_stat * src)28 void blk_rq_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
29 {
30 	if (!src->nr_samples)
31 		return;
32 
33 	dst->min = min(dst->min, src->min);
34 	dst->max = max(dst->max, src->max);
35 
36 	dst->mean = div_u64(src->batch + dst->mean * dst->nr_samples,
37 				dst->nr_samples + src->nr_samples);
38 
39 	dst->nr_samples += src->nr_samples;
40 }
41 
blk_rq_stat_add(struct blk_rq_stat * stat,u64 value)42 void blk_rq_stat_add(struct blk_rq_stat *stat, u64 value)
43 {
44 	stat->min = min(stat->min, value);
45 	stat->max = max(stat->max, value);
46 	stat->batch += value;
47 	stat->nr_samples++;
48 }
49 
blk_stat_add(struct request * rq,u64 now)50 void blk_stat_add(struct request *rq, u64 now)
51 {
52 	struct request_queue *q = rq->q;
53 	struct blk_stat_callback *cb;
54 	struct blk_rq_stat *stat;
55 	int bucket;
56 	u64 value;
57 
58 	value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
59 
60 	blk_throtl_stat_add(rq, value);
61 
62 	rcu_read_lock();
63 	list_for_each_entry_rcu(cb, &q->stats->callbacks, list) {
64 		if (!blk_stat_is_active(cb))
65 			continue;
66 
67 		bucket = cb->bucket_fn(rq);
68 		if (bucket < 0)
69 			continue;
70 
71 		stat = &get_cpu_ptr(cb->cpu_stat)[bucket];
72 		blk_rq_stat_add(stat, value);
73 		put_cpu_ptr(cb->cpu_stat);
74 	}
75 	rcu_read_unlock();
76 }
77 
blk_stat_timer_fn(struct timer_list * t)78 static void blk_stat_timer_fn(struct timer_list *t)
79 {
80 	struct blk_stat_callback *cb = from_timer(cb, t, timer);
81 	unsigned int bucket;
82 	int cpu;
83 
84 	for (bucket = 0; bucket < cb->buckets; bucket++)
85 		blk_rq_stat_init(&cb->stat[bucket]);
86 
87 	for_each_online_cpu(cpu) {
88 		struct blk_rq_stat *cpu_stat;
89 
90 		cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
91 		for (bucket = 0; bucket < cb->buckets; bucket++) {
92 			blk_rq_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]);
93 			blk_rq_stat_init(&cpu_stat[bucket]);
94 		}
95 	}
96 
97 	cb->timer_fn(cb);
98 }
99 
100 struct blk_stat_callback *
blk_stat_alloc_callback(void (* timer_fn)(struct blk_stat_callback *),int (* bucket_fn)(const struct request *),unsigned int buckets,void * data)101 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *),
102 			int (*bucket_fn)(const struct request *),
103 			unsigned int buckets, void *data)
104 {
105 	struct blk_stat_callback *cb;
106 
107 	cb = kmalloc(sizeof(*cb), GFP_KERNEL);
108 	if (!cb)
109 		return NULL;
110 
111 	cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat),
112 				 GFP_KERNEL);
113 	if (!cb->stat) {
114 		kfree(cb);
115 		return NULL;
116 	}
117 	cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat),
118 				      __alignof__(struct blk_rq_stat));
119 	if (!cb->cpu_stat) {
120 		kfree(cb->stat);
121 		kfree(cb);
122 		return NULL;
123 	}
124 
125 	cb->timer_fn = timer_fn;
126 	cb->bucket_fn = bucket_fn;
127 	cb->data = data;
128 	cb->buckets = buckets;
129 	timer_setup(&cb->timer, blk_stat_timer_fn, 0);
130 
131 	return cb;
132 }
133 EXPORT_SYMBOL_GPL(blk_stat_alloc_callback);
134 
blk_stat_add_callback(struct request_queue * q,struct blk_stat_callback * cb)135 void blk_stat_add_callback(struct request_queue *q,
136 			   struct blk_stat_callback *cb)
137 {
138 	unsigned int bucket;
139 	int cpu;
140 
141 	for_each_possible_cpu(cpu) {
142 		struct blk_rq_stat *cpu_stat;
143 
144 		cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu);
145 		for (bucket = 0; bucket < cb->buckets; bucket++)
146 			blk_rq_stat_init(&cpu_stat[bucket]);
147 	}
148 
149 	spin_lock(&q->stats->lock);
150 	list_add_tail_rcu(&cb->list, &q->stats->callbacks);
151 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
152 	spin_unlock(&q->stats->lock);
153 }
154 EXPORT_SYMBOL_GPL(blk_stat_add_callback);
155 
blk_stat_remove_callback(struct request_queue * q,struct blk_stat_callback * cb)156 void blk_stat_remove_callback(struct request_queue *q,
157 			      struct blk_stat_callback *cb)
158 {
159 	spin_lock(&q->stats->lock);
160 	list_del_rcu(&cb->list);
161 	if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting)
162 		blk_queue_flag_clear(QUEUE_FLAG_STATS, q);
163 	spin_unlock(&q->stats->lock);
164 
165 	del_timer_sync(&cb->timer);
166 }
167 EXPORT_SYMBOL_GPL(blk_stat_remove_callback);
168 
blk_stat_free_callback_rcu(struct rcu_head * head)169 static void blk_stat_free_callback_rcu(struct rcu_head *head)
170 {
171 	struct blk_stat_callback *cb;
172 
173 	cb = container_of(head, struct blk_stat_callback, rcu);
174 	free_percpu(cb->cpu_stat);
175 	kfree(cb->stat);
176 	kfree(cb);
177 }
178 
blk_stat_free_callback(struct blk_stat_callback * cb)179 void blk_stat_free_callback(struct blk_stat_callback *cb)
180 {
181 	if (cb)
182 		call_rcu(&cb->rcu, blk_stat_free_callback_rcu);
183 }
184 EXPORT_SYMBOL_GPL(blk_stat_free_callback);
185 
blk_stat_enable_accounting(struct request_queue * q)186 void blk_stat_enable_accounting(struct request_queue *q)
187 {
188 	spin_lock(&q->stats->lock);
189 	q->stats->enable_accounting = true;
190 	blk_queue_flag_set(QUEUE_FLAG_STATS, q);
191 	spin_unlock(&q->stats->lock);
192 }
193 
blk_alloc_queue_stats(void)194 struct blk_queue_stats *blk_alloc_queue_stats(void)
195 {
196 	struct blk_queue_stats *stats;
197 
198 	stats = kmalloc(sizeof(*stats), GFP_KERNEL);
199 	if (!stats)
200 		return NULL;
201 
202 	INIT_LIST_HEAD(&stats->callbacks);
203 	spin_lock_init(&stats->lock);
204 	stats->enable_accounting = false;
205 
206 	return stats;
207 }
208 
blk_free_queue_stats(struct blk_queue_stats * stats)209 void blk_free_queue_stats(struct blk_queue_stats *stats)
210 {
211 	if (!stats)
212 		return;
213 
214 	WARN_ON(!list_empty(&stats->callbacks));
215 
216 	kfree(stats);
217 }
218