Indeed tool iostat's await is not good enough, which is somewhat sketchy
and could not show request's latency on device driver's side.
Here we add a new counter to track io request's d2c time, also with this
patch, we can extend iostat to show this value easily.
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx>
---
block/blk-core.c | 3 +++
block/genhd.c | 7 +++++--
block/partition-generic.c | 8 ++++++--
include/linux/genhd.h | 4 ++++
4 files changed, 18 insertions(+), 4 deletions(-)
diff --git a/block/blk-core.c b/block/blk-core.c
index ee1b35fe8572..b0449ec80a7d 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1257,6 +1257,9 @@ void blk_account_io_done(struct request *req, u64 now)
update_io_ticks(part, jiffies);
part_stat_inc(part, ios[sgrp]);
part_stat_add(part, nsecs[sgrp], now - req->start_time_ns);
+ if (req->io_start_time_ns)
+ part_stat_add(part, d2c_nsecs[sgrp],
+ now - req->io_start_time_ns);
part_stat_add(part, time_in_queue, nsecs_to_jiffies64(now - req->start_time_ns));
part_dec_in_flight(req->q, part, rq_data_dir(req));
diff --git a/block/genhd.c b/block/genhd.c
index 24654e1d83e6..727bc1de1a74 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1377,7 +1377,7 @@ static int diskstats_show(struct seq_file *seqf, void *v)
"%lu %lu %lu %u "
"%lu %lu %lu %u "
"%u %u %u "
- "%lu %lu %lu %u\n",
+ "%lu %lu %lu %u %u %u %u\n",
MAJOR(part_devt(hd)), MINOR(part_devt(hd)),
disk_name(gp, hd->partno, buf),
part_stat_read(hd, ios[STAT_READ]),
@@ -1394,7 +1394,10 @@ static int diskstats_show(struct seq_file *seqf, void *v)
part_stat_read(hd, ios[STAT_DISCARD]),
part_stat_read(hd, merges[STAT_DISCARD]),
part_stat_read(hd, sectors[STAT_DISCARD]),
- (unsigned int)part_stat_read_msecs(hd, STAT_DISCARD)
+ (unsigned int)part_stat_read_msecs(hd, STAT_DISCARD),
+ (unsigned int)part_stat_read_d2c_msecs(hd, STAT_READ),
+ (unsigned int)part_stat_read_d2c_msecs(hd, STAT_WRITE),
+ (unsigned int)part_stat_read_d2c_msecs(hd, STAT_DISCARD)
);
}
disk_part_iter_exit(&piter);
diff --git a/block/partition-generic.c b/block/partition-generic.c
index aee643ce13d1..0635a46a31dd 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -127,7 +127,7 @@ ssize_t part_stat_show(struct device *dev,
"%8lu %8lu %8llu %8u "
"%8lu %8lu %8llu %8u "
"%8u %8u %8u "
- "%8lu %8lu %8llu %8u"
+ "%8lu %8lu %8llu %8u %8u %8u %8u %8u"
"\n",
part_stat_read(p, ios[STAT_READ]),
part_stat_read(p, merges[STAT_READ]),
@@ -143,7 +143,11 @@ ssize_t part_stat_show(struct device *dev,
part_stat_read(p, ios[STAT_DISCARD]),
part_stat_read(p, merges[STAT_DISCARD]),
(unsigned long long)part_stat_read(p, sectors[STAT_DISCARD]),
- (unsigned int)part_stat_read_msecs(p, STAT_DISCARD));
+ (unsigned int)part_stat_read_msecs(p, STAT_DISCARD),
+ (unsigned int)part_stat_read_msecs(p, STAT_DISCARD),
+ (unsigned int)part_stat_read_d2c_msecs(p, STAT_READ),
+ (unsigned int)part_stat_read_d2c_msecs(p, STAT_WRITE),
+ (unsigned int)part_stat_read_d2c_msecs(p, STAT_DISCARD));
}
ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 8b5330dd5ac0..f80ba947cac2 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -85,6 +85,7 @@ struct partition {
struct disk_stats {
u64 nsecs[NR_STAT_GROUPS];
+ u64 d2c_nsecs[NR_STAT_GROUPS];
unsigned long sectors[NR_STAT_GROUPS];
unsigned long ios[NR_STAT_GROUPS];
unsigned long merges[NR_STAT_GROUPS];
@@ -367,6 +368,9 @@ static inline void free_part_stats(struct hd_struct *part)
#define part_stat_read_msecs(part, which) \
div_u64(part_stat_read(part, nsecs[which]), NSEC_PER_MSEC)
+#define part_stat_read_d2c_msecs(part, which) \
+ div_u64(part_stat_read(part, d2c_nsecs[which]), NSEC_PER_MSEC)
+
#define part_stat_read_accum(part, field) \
(part_stat_read(part, field[STAT_READ]) + \
part_stat_read(part, field[STAT_WRITE]) + \
--
2.17.2
