Commit eca8b53a authored by Shaohua Li's avatar Shaohua Li Committed by Jens Axboe
Browse files

blk-stat: delete useless code 



Fix two issues:
- the per-cpu stat flush is unnecessary, nobody uses per-cpu stat except
  sum it to global stat. We can do the calculation there. The flush just
  wastes cpu time.
- some fields are signed int/s64. I don't see the point.

Reviewed-by: default avatarOmar Sandoval <osandov@fb.com>
Signed-off-by: default avatarShaohua Li <shli@fb.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 53cfdc10

block/blk-stat.c

+7 −38
Original line number Diff line number Diff line
@@ -11,8 +11,6 @@ 
#include "blk-mq.h"

#include "blk.h"



#define BLK_RQ_STAT_BATCH	64



struct blk_queue_stats {

	struct list_head callbacks;

	spinlock_t lock;
@@ -23,45 +21,21 @@ static void blk_stat_init(struct blk_rq_stat *stat) 
{

	stat->min = -1ULL;

	stat->max = stat->nr_samples = stat->mean = 0;

	stat->batch = stat->nr_batch = 0;

}



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;

	stat->batch = 0;

}



/* src is a per-cpu stat, mean isn't initialized */

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->mean = div_u64(src->batch + dst->mean * dst->nr_samples,

				dst->nr_samples + src->nr_samples);

	}



	dst->nr_samples += src->nr_samples;

}
@@ -69,13 +43,8 @@ static void __blk_stat_add(struct blk_rq_stat *stat, u64 value) 
{

	stat->min = min(stat->min, value);

	stat->max = max(stat->max, 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++;

	stat->nr_samples++;

}



void blk_stat_add(struct request *rq)
@@ -84,7 +53,7 @@ void blk_stat_add(struct request *rq) 
	struct blk_stat_callback *cb;

	struct blk_rq_stat *stat;

	int bucket;

	s64 now, value;

	u64 now, value;



	now = __blk_stat_time(ktime_to_ns(ktime_get()));

	if (now < blk_stat_time(&rq->issue_stat))

include/linux/blk_types.h

+2 −3
Original line number Diff line number Diff line
@@ -329,11 +329,10 @@ static inline bool blk_qc_t_is_internal(blk_qc_t cookie) 
}



struct blk_rq_stat {

	s64 mean;

	u64 mean;

	u64 min;

	u64 max;

	s32 nr_samples;

	s32 nr_batch;

	u32 nr_samples;

	u64 batch;

};

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