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/*
* Block stat tracking code
*
* Copyright (C) 2016 Jens Axboe
*/
#include <linux/kernel.h>
#include <linux/blk-mq.h>
#include "blk-stat.h"
#include "blk-mq.h"
#define BLK_RQ_STAT_BATCH 64
static void blk_stat_flush_batch(struct blk_rq_stat *stat)
{
const s32 nr_batch = READ_ONCE(stat->nr_batch);
const s32 nr_samples = READ_ONCE(stat->nr_samples);
if (!nr_batch)
return;
if (!nr_samples)
stat->mean = div64_s64(stat->batch, nr_batch);
else {
stat->mean = div64_s64((stat->mean * nr_samples) +
stat->batch,
nr_batch + nr_samples);
}
stat->nr_samples += nr_batch;
stat->nr_batch = stat->batch = 0;
}
static void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *src)
{
blk_stat_flush_batch(src);
if (!src->nr_samples)
return;
dst->min = min(dst->min, src->min);
dst->max = max(dst->max, src->max);
if (!dst->nr_samples)
dst->mean = src->mean;
else {
dst->mean = div64_s64((src->mean * src->nr_samples) +
(dst->mean * dst->nr_samples),
dst->nr_samples + src->nr_samples);
}
dst->nr_samples += src->nr_samples;
}
static void blk_mq_stat_get(struct request_queue *q, struct blk_rq_stat *dst)
{
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
uint64_t latest = 0;
int i, j, nr;
blk_stat_init(&dst[READ]);
blk_stat_init(&dst[WRITE]);
nr = 0;
do {
uint64_t newest = 0;
queue_for_each_hw_ctx(q, hctx, i) {
hctx_for_each_ctx(hctx, ctx, j) {
blk_stat_flush_batch(&ctx->stat[READ]);
blk_stat_flush_batch(&ctx->stat[WRITE]);
if (!ctx->stat[READ].nr_samples &&
!ctx->stat[WRITE].nr_samples)
continue;
if (ctx->stat[READ].time > newest)
newest = ctx->stat[READ].time;
if (ctx->stat[WRITE].time > newest)
newest = ctx->stat[WRITE].time;
}
}
/*
* No samples
*/
if (!newest)
break;
if (newest > latest)
latest = newest;
queue_for_each_hw_ctx(q, hctx, i) {
hctx_for_each_ctx(hctx, ctx, j) {
if (ctx->stat[READ].time == newest) {
blk_stat_sum(&dst[READ],
&ctx->stat[READ]);
nr++;
}
if (ctx->stat[WRITE].time == newest) {
blk_stat_sum(&dst[WRITE],
&ctx->stat[WRITE]);
nr++;
}
}
}
/*
* If we race on finding an entry, just loop back again.
* Should be very rare.
*/
} while (!nr);
dst[READ].time = dst[WRITE].time = latest;
}
void blk_queue_stat_get(struct request_queue *q, struct blk_rq_stat *dst)
{
if (q->mq_ops)
blk_mq_stat_get(q, dst);
else {
blk_stat_flush_batch(&q->rq_stats[READ]);
blk_stat_flush_batch(&q->rq_stats[WRITE]);
memcpy(&dst[READ], &q->rq_stats[READ],
sizeof(struct blk_rq_stat));
memcpy(&dst[WRITE], &q->rq_stats[WRITE],
sizeof(struct blk_rq_stat));
}
}
void blk_hctx_stat_get(struct blk_mq_hw_ctx *hctx, struct blk_rq_stat *dst)
{
struct blk_mq_ctx *ctx;
unsigned int i, nr;
nr = 0;
do {
uint64_t newest = 0;
hctx_for_each_ctx(hctx, ctx, i) {
blk_stat_flush_batch(&ctx->stat[READ]);
blk_stat_flush_batch(&ctx->stat[WRITE]);
if (!ctx->stat[READ].nr_samples &&
!ctx->stat[WRITE].nr_samples)
continue;
if (ctx->stat[READ].time > newest)
newest = ctx->stat[READ].time;
if (ctx->stat[WRITE].time > newest)
newest = ctx->stat[WRITE].time;
}
if (!newest)
break;
hctx_for_each_ctx(hctx, ctx, i) {
if (ctx->stat[READ].time == newest) {
blk_stat_sum(&dst[READ], &ctx->stat[READ]);
nr++;
}
if (ctx->stat[WRITE].time == newest) {
blk_stat_sum(&dst[WRITE], &ctx->stat[WRITE]);
nr++;
}
}
/*
* If we race on finding an entry, just loop back again.
* Should be very rare, as the window is only updated
* occasionally
*/
} while (!nr);
}
static void __blk_stat_init(struct blk_rq_stat *stat, s64 time_now)
{
stat->min = -1ULL;
stat->max = stat->nr_samples = stat->mean = 0;
stat->batch = stat->nr_batch = 0;
stat->time = time_now & BLK_STAT_NSEC_MASK;
}
void blk_stat_init(struct blk_rq_stat *stat)
{
__blk_stat_init(stat, ktime_to_ns(ktime_get()));
}
static bool __blk_stat_is_current(struct blk_rq_stat *stat, s64 now)
{
return (now & BLK_STAT_NSEC_MASK) == (stat->time & BLK_STAT_NSEC_MASK);
}
bool blk_stat_is_current(struct blk_rq_stat *stat)
{
return __blk_stat_is_current(stat, ktime_to_ns(ktime_get()));
}
void blk_stat_add(struct blk_rq_stat *stat, struct request *rq)
{
s64 now, value;
now = __blk_stat_time(ktime_to_ns(ktime_get()));
if (now < blk_stat_time(&rq->issue_stat))
return;
if (!__blk_stat_is_current(stat, now))
__blk_stat_init(stat, now);
value = now - blk_stat_time(&rq->issue_stat);
if (value > stat->max)
stat->max = value;
if (value < stat->min)
stat->min = value;
if (stat->batch + value < stat->batch ||
stat->nr_batch + 1 == BLK_RQ_STAT_BATCH)
blk_stat_flush_batch(stat);
stat->batch += value;
stat->nr_batch++;
}
void blk_stat_clear(struct request_queue *q)
{
if (q->mq_ops) {
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx;
int i, j;
queue_for_each_hw_ctx(q, hctx, i) {
hctx_for_each_ctx(hctx, ctx, j) {
blk_stat_init(&ctx->stat[READ]);
blk_stat_init(&ctx->stat[WRITE]);
}
}
} else {
blk_stat_init(&q->rq_stats[READ]);
blk_stat_init(&q->rq_stats[WRITE]);
}
}
void blk_stat_set_issue_time(struct blk_issue_stat *stat)
{
stat->time = (stat->time & BLK_STAT_MASK) |
(ktime_to_ns(ktime_get()) & BLK_STAT_TIME_MASK);
}
/*
* Enable stat tracking, return whether it was enabled
*/
bool blk_stat_enable(struct request_queue *q)
{
if (!test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
set_bit(QUEUE_FLAG_STATS, &q->queue_flags);
return false;
}
return true;
}
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