lkml.org 
[lkml]   [2019]   [Apr]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Subject[PATCH 3/3] block/diskstats: more accurate approximation of io_ticks for slow disks
From
Date
Currently io_ticks is approximated by adding one at each
start and end of requests if jiffies has changed.
This works perfectly for requests shorter than a jiffy.

Fix for slow requests is simple: at the end of request add
count of jiffies passed since last update.

Fixes: 5b18b5a73760 ("block: delete part_round_stats and switch to less precise counting")
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
block/bio.c | 8 ++++----
block/blk-core.c | 4 ++--
include/linux/genhd.h | 2 +-
3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/block/bio.c b/block/bio.c
index c0a60f3e9b7b..245056797999 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -1729,14 +1729,14 @@ void bio_check_pages_dirty(struct bio *bio)
schedule_work(&bio_dirty_work);
}

-void update_io_ticks(struct hd_struct *part, unsigned long now)
+void update_io_ticks(struct hd_struct *part, unsigned long now, bool end)
{
unsigned long stamp;
again:
stamp = READ_ONCE(part->stamp);
if (unlikely(stamp != now)) {
if (likely(cmpxchg(&part->stamp, stamp, now) == stamp)) {
- __part_stat_add(part, io_ticks, 1);
+ __part_stat_add(part, io_ticks, end ? now - stamp : 1);
}
}
if (part->partno) {
@@ -1752,7 +1752,7 @@ void generic_start_io_acct(struct request_queue *q, int op,

part_stat_lock();

- update_io_ticks(part, jiffies);
+ update_io_ticks(part, jiffies, false);
part_stat_inc(part, ios[sgrp]);
part_stat_add(part, sectors[sgrp], sectors);
part_inc_in_flight(q, part, op_is_write(op));
@@ -1770,7 +1770,7 @@ void generic_end_io_acct(struct request_queue *q, int req_op,

part_stat_lock();

- update_io_ticks(part, now);
+ update_io_ticks(part, now, true);
part_stat_add(part, nsecs[sgrp], jiffies_to_nsecs(duration));
part_dec_in_flight(q, part, op_is_write(req_op));

diff --git a/block/blk-core.c b/block/blk-core.c
index d89168b167e9..6e8f0b9e7731 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1334,7 +1334,7 @@ void blk_account_io_done(struct request *req, u64 now)
part_stat_lock();
part = req->part;

- update_io_ticks(part, jiffies);
+ update_io_ticks(part, jiffies, true);
part_stat_inc(part, ios[sgrp]);
part_stat_add(part, nsecs[sgrp], now - req->start_time_ns);
part_dec_in_flight(req->q, part, rq_data_dir(req));
@@ -1375,7 +1375,7 @@ void blk_account_io_start(struct request *rq, bool new_io)
rq->part = part;
}

- update_io_ticks(part, jiffies);
+ update_io_ticks(part, jiffies, false);

part_stat_unlock();
}
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 2f5a9ed7e86e..8ece8e02c609 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -410,7 +410,7 @@ static inline void free_part_info(struct hd_struct *part)
kfree(part->info);
}

-void update_io_ticks(struct hd_struct *part, unsigned long now);
+void update_io_ticks(struct hd_struct *part, unsigned long now, bool end);

/* block/genhd.c */
extern void device_add_disk(struct device *parent, struct gendisk *disk,
\
 
 \ /
  Last update: 2019-04-01 18:00    [W:0.054 / U:12.076 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site