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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"
void blk_stat_sum(struct blk_rq_stat *dst, struct blk_rq_stat *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;
int i, j, nr;
blk_stat_init(&dst[0]);
blk_stat_init(&dst[1]);
nr = 0;
do {
uint64_t newest = 0;
queue_for_each_hw_ctx(q, hctx, i) {
hctx_for_each_ctx(hctx, ctx, j) {
if (!ctx->stat[0].nr_samples &&
!ctx->stat[1].nr_samples)
continue;
if (ctx->stat[0].time > newest)
newest = ctx->stat[0].time;
if (ctx->stat[1].time > newest)
newest = ctx->stat[1].time;
}
}
/*
* No samples
*/
if (!newest)
break;
queue_for_each_hw_ctx(q, hctx, i) {
hctx_for_each_ctx(hctx, ctx, j) {
if (ctx->stat[0].time == newest) {
blk_stat_sum(&dst[0], &ctx->stat[0]);
nr++;
}
if (ctx->stat[1].time == newest) {
blk_stat_sum(&dst[1], &ctx->stat[1]);
nr++;
}
}
}
/*
* If we race on finding an entry, just loop back again.
* Should be very rare.
*/
} while (!nr);
}
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 {
memcpy(&dst[0], &q->rq_stats[0], sizeof(struct blk_rq_stat));
memcpy(&dst[1], &q->rq_stats[1], 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) {
if (!ctx->stat[0].nr_samples &&
!ctx->stat[1].nr_samples)
continue;
if (ctx->stat[0].time > newest)
newest = ctx->stat[0].time;
if (ctx->stat[1].time > newest)
newest = ctx->stat[1].time;
}
if (!newest)
break;
hctx_for_each_ctx(hctx, ctx, i) {
if (ctx->stat[0].time == newest) {
blk_stat_sum(&dst[0], &ctx->stat[0]);
nr++;
}
if (ctx->stat[1].time == newest) {
blk_stat_sum(&dst[1], &ctx->stat[1]);
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->time = time_now & BLK_STAT_MASK;
}
void blk_stat_init(struct blk_rq_stat *stat)
{
__blk_stat_init(stat, ktime_to_ns(ktime_get()));
}
void blk_stat_add(struct blk_rq_stat *stat, struct request *rq)
{
s64 delta, now, value;
u64 rq_time = wbt_issue_stat_get_time(&rq->wb_stat);
now = ktime_to_ns(ktime_get());
if (now < rq_time)
return;
if ((now & BLK_STAT_MASK) != (stat->time & BLK_STAT_MASK))
__blk_stat_init(stat, now);
value = now - rq_time;
if (value > stat->max)
stat->max = value;
if (value < stat->min)
stat->min = value;
delta = value - stat->mean;
if (delta)
stat->mean += div64_s64(delta, stat->nr_samples + 1);
stat->nr_samples++;
}
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[0]);
blk_stat_init(&ctx->stat[1]);
}
}
} else {
blk_stat_init(&q->rq_stats[0]);
blk_stat_init(&q->rq_stats[1]);
}
}
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