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 #define BLK_RQ_STAT_BATCH 64 15 16 struct blk_queue_stats { 17 struct list_head callbacks; 18 spinlock_t lock; 19 bool enable_accounting; 20 }; 21 22 static void blk_stat_init(struct blk_rq_stat *stat) 23 { 24 stat->min = -1ULL; 25 stat->max = stat->nr_samples = stat->mean = 0; 26 stat->batch = stat->nr_batch = 0; 27 } 28 29 static void blk_stat_flush_batch(struct blk_rq_stat *stat) 30 { 31 const s32 nr_batch = READ_ONCE(stat->nr_batch); 32 const s32 nr_samples = READ_ONCE(stat->nr_samples); 33 34 if (!nr_batch) 35 return; 36 if (!nr_samples) 37 stat->mean = div64_s64(stat->batch, nr_batch); 38 else { 39 stat->mean = div64_s64((stat->mean * nr_samples) + 40 stat->batch, 41 nr_batch + nr_samples); 42 } 43 44 stat->nr_samples += nr_batch; 45 stat->nr_batch = stat->batch = 0; 46 } 47 48 static void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src) 49 { 50 blk_stat_flush_batch(src); 51 52 if (!src->nr_samples) 53 return; 54 55 dst->min = min(dst->min, src->min); 56 dst->max = max(dst->max, src->max); 57 58 if (!dst->nr_samples) 59 dst->mean = src->mean; 60 else { 61 dst->mean = div64_s64((src->mean * src->nr_samples) + 62 (dst->mean * dst->nr_samples), 63 dst->nr_samples + src->nr_samples); 64 } 65 dst->nr_samples += src->nr_samples; 66 } 67 68 static void __blk_stat_add(struct blk_rq_stat *stat, u64 value) 69 { 70 stat->min = min(stat->min, value); 71 stat->max = max(stat->max, value); 72 73 if (stat->batch + value < stat->batch || 74 stat->nr_batch + 1 == BLK_RQ_STAT_BATCH) 75 blk_stat_flush_batch(stat); 76 77 stat->batch += value; 78 stat->nr_batch++; 79 } 80 81 void blk_stat_add(struct request *rq) 82 { 83 struct request_queue *q = rq->q; 84 struct blk_stat_callback *cb; 85 struct blk_rq_stat *stat; 86 int bucket; 87 s64 now, value; 88 89 now = __blk_stat_time(ktime_to_ns(ktime_get())); 90 if (now < blk_stat_time(&rq->issue_stat)) 91 return; 92 93 value = now - blk_stat_time(&rq->issue_stat); 94 95 blk_throtl_stat_add(rq, value); 96 97 rcu_read_lock(); 98 list_for_each_entry_rcu(cb, &q->stats->callbacks, list) { 99 if (blk_stat_is_active(cb)) { 100 bucket = cb->bucket_fn(rq); 101 if (bucket < 0) 102 continue; 103 stat = &this_cpu_ptr(cb->cpu_stat)[bucket]; 104 __blk_stat_add(stat, value); 105 } 106 } 107 rcu_read_unlock(); 108 } 109 110 static void blk_stat_timer_fn(unsigned long data) 111 { 112 struct blk_stat_callback *cb = (void *)data; 113 unsigned int bucket; 114 int cpu; 115 116 for (bucket = 0; bucket < cb->buckets; bucket++) 117 blk_stat_init(&cb->stat[bucket]); 118 119 for_each_online_cpu(cpu) { 120 struct blk_rq_stat *cpu_stat; 121 122 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu); 123 for (bucket = 0; bucket < cb->buckets; bucket++) { 124 blk_stat_sum(&cb->stat[bucket], &cpu_stat[bucket]); 125 blk_stat_init(&cpu_stat[bucket]); 126 } 127 } 128 129 cb->timer_fn(cb); 130 } 131 132 struct blk_stat_callback * 133 blk_stat_alloc_callback(void (*timer_fn)(struct blk_stat_callback *), 134 int (*bucket_fn)(const struct request *), 135 unsigned int buckets, void *data) 136 { 137 struct blk_stat_callback *cb; 138 139 cb = kmalloc(sizeof(*cb), GFP_KERNEL); 140 if (!cb) 141 return NULL; 142 143 cb->stat = kmalloc_array(buckets, sizeof(struct blk_rq_stat), 144 GFP_KERNEL); 145 if (!cb->stat) { 146 kfree(cb); 147 return NULL; 148 } 149 cb->cpu_stat = __alloc_percpu(buckets * sizeof(struct blk_rq_stat), 150 __alignof__(struct blk_rq_stat)); 151 if (!cb->cpu_stat) { 152 kfree(cb->stat); 153 kfree(cb); 154 return NULL; 155 } 156 157 cb->timer_fn = timer_fn; 158 cb->bucket_fn = bucket_fn; 159 cb->data = data; 160 cb->buckets = buckets; 161 setup_timer(&cb->timer, blk_stat_timer_fn, (unsigned long)cb); 162 163 return cb; 164 } 165 EXPORT_SYMBOL_GPL(blk_stat_alloc_callback); 166 167 void blk_stat_add_callback(struct request_queue *q, 168 struct blk_stat_callback *cb) 169 { 170 unsigned int bucket; 171 int cpu; 172 173 for_each_possible_cpu(cpu) { 174 struct blk_rq_stat *cpu_stat; 175 176 cpu_stat = per_cpu_ptr(cb->cpu_stat, cpu); 177 for (bucket = 0; bucket < cb->buckets; bucket++) 178 blk_stat_init(&cpu_stat[bucket]); 179 } 180 181 spin_lock(&q->stats->lock); 182 list_add_tail_rcu(&cb->list, &q->stats->callbacks); 183 set_bit(QUEUE_FLAG_STATS, &q->queue_flags); 184 spin_unlock(&q->stats->lock); 185 } 186 EXPORT_SYMBOL_GPL(blk_stat_add_callback); 187 188 void blk_stat_remove_callback(struct request_queue *q, 189 struct blk_stat_callback *cb) 190 { 191 spin_lock(&q->stats->lock); 192 list_del_rcu(&cb->list); 193 if (list_empty(&q->stats->callbacks) && !q->stats->enable_accounting) 194 clear_bit(QUEUE_FLAG_STATS, &q->queue_flags); 195 spin_unlock(&q->stats->lock); 196 197 del_timer_sync(&cb->timer); 198 } 199 EXPORT_SYMBOL_GPL(blk_stat_remove_callback); 200 201 static void blk_stat_free_callback_rcu(struct rcu_head *head) 202 { 203 struct blk_stat_callback *cb; 204 205 cb = container_of(head, struct blk_stat_callback, rcu); 206 free_percpu(cb->cpu_stat); 207 kfree(cb->stat); 208 kfree(cb); 209 } 210 211 void blk_stat_free_callback(struct blk_stat_callback *cb) 212 { 213 if (cb) 214 call_rcu(&cb->rcu, blk_stat_free_callback_rcu); 215 } 216 EXPORT_SYMBOL_GPL(blk_stat_free_callback); 217 218 void blk_stat_enable_accounting(struct request_queue *q) 219 { 220 spin_lock(&q->stats->lock); 221 q->stats->enable_accounting = true; 222 set_bit(QUEUE_FLAG_STATS, &q->queue_flags); 223 spin_unlock(&q->stats->lock); 224 } 225 226 struct blk_queue_stats *blk_alloc_queue_stats(void) 227 { 228 struct blk_queue_stats *stats; 229 230 stats = kmalloc(sizeof(*stats), GFP_KERNEL); 231 if (!stats) 232 return NULL; 233 234 INIT_LIST_HEAD(&stats->callbacks); 235 spin_lock_init(&stats->lock); 236 stats->enable_accounting = false; 237 238 return stats; 239 } 240 241 void blk_free_queue_stats(struct blk_queue_stats *stats) 242 { 243 if (!stats) 244 return; 245 246 WARN_ON(!list_empty(&stats->callbacks)); 247 248 kfree(stats); 249 } 250