[PATCH 5/6] block: Track DISCARD statistics and output them in stat and diskstat
From: Tejun Heo
Date: Wed Jul 18 2018 - 07:48:10 EST
From: Michael Callahan <michaelcallahan@xxxxxx>
Add tracking of REQ_OP_DISCARD ios to the partition statistics and
append them to the various stat files in /sys as well as
/proc/diskstats. These are tracked with the same four stats as reads
and writes:
Number of discard ios completed.
Number of discard ios merged
Number of discard sectors completed
Milliseconds spent on discard requests
This is done via adding a new STAT_DISCARD define to genhd.h and then
using it to index that stat field for discard requests.
tj: Refreshed on top of v4.17 and other previous updates.
Signed-off-by: Michael Callahan <michaelcallahan@xxxxxx>
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Andy Newell <newella@xxxxxx>
---
Documentation/ABI/testing/procfs-diskstats | 10 ++++++++
Documentation/block/stat.txt | 28 ++++++++++++----------
Documentation/iostats.txt | 15 ++++++++++++
block/genhd.c | 13 +++++++---
block/partition-generic.c | 9 +++++--
include/linux/blk_types.h | 8 +++++++
include/linux/genhd.h | 3 ++-
7 files changed, 68 insertions(+), 18 deletions(-)
diff --git a/Documentation/ABI/testing/procfs-diskstats b/Documentation/ABI/testing/procfs-diskstats
index f91a973a37fe..abac31d216de 100644
--- a/Documentation/ABI/testing/procfs-diskstats
+++ b/Documentation/ABI/testing/procfs-diskstats
@@ -5,6 +5,7 @@ Contact: Jerome Marchand <jmarchan@xxxxxxxxxx>
The /proc/diskstats file displays the I/O statistics
of block devices. Each line contains the following 14
fields:
+
1 - major number
2 - minor mumber
3 - device name
@@ -19,4 +20,13 @@ Contact: Jerome Marchand <jmarchan@xxxxxxxxxx>
12 - I/Os currently in progress
13 - time spent doing I/Os (ms)
14 - weighted time spent doing I/Os (ms)
+
+ Kernel 4.18+ appends four more fields for discard
+ tracking putting the total at 18:
+
+ 15 - discards completed successfully
+ 16 - discards merged
+ 17 - sectors discarded
+ 18 - time spent discarding
+
For more details refer to Documentation/iostats.txt
diff --git a/Documentation/block/stat.txt b/Documentation/block/stat.txt
index 0dbc946de2ea..0aace9cc536c 100644
--- a/Documentation/block/stat.txt
+++ b/Documentation/block/stat.txt
@@ -31,28 +31,32 @@ write ticks milliseconds total wait time for write requests
in_flight requests number of I/Os currently in flight
io_ticks milliseconds total time this block device has been active
time_in_queue milliseconds total wait time for all requests
+discard I/Os requests number of discard I/Os processed
+discard merges requests number of discard I/Os merged with in-queue I/O
+discard sectors sectors number of sectors discarded
+discard ticks milliseconds total wait time for discard requests
-read I/Os, write I/Os
-=====================
+read I/Os, write I/Os, discard I/0s
+===================================
These values increment when an I/O request completes.
-read merges, write merges
-=========================
+read merges, write merges, discard merges
+=========================================
These values increment when an I/O request is merged with an
already-queued I/O request.
-read sectors, write sectors
-===========================
+read sectors, write sectors, discard_sectors
+============================================
-These values count the number of sectors read from or written to this
-block device. The "sectors" in question are the standard UNIX 512-byte
-sectors, not any device- or filesystem-specific block size. The
-counters are incremented when the I/O completes.
+These values count the number of sectors read from, written to, or
+discarded from this block device. The "sectors" in question are the
+standard UNIX 512-byte sectors, not any device- or filesystem-specific
+block size. The counters are incremented when the I/O completes.
-read ticks, write ticks
-=======================
+read ticks, write ticks, discard ticks
+======================================
These values count the number of milliseconds that I/O requests have
waited on this block device. If there are multiple I/O requests waiting,
diff --git a/Documentation/iostats.txt b/Documentation/iostats.txt
index 04d394a2e06c..49df45f90e8a 100644
--- a/Documentation/iostats.txt
+++ b/Documentation/iostats.txt
@@ -31,6 +31,9 @@ and so should not differ.
3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160
3 1 hda1 35486 38030 38030 38030
+ 4.18+ diskstats:
+ 3 0 hda 446216 784926 9550688 4382310 424847 312726 5922052 19310380 0 3376340 23705160 0 0 0 0
+
On 2.4 you might execute ``grep 'hda ' /proc/partitions``. On 2.6+, you have
a choice of ``cat /sys/block/hda/stat`` or ``grep 'hda ' /proc/diskstats``.
@@ -101,6 +104,18 @@ Field 11 -- weighted # of milliseconds spent doing I/Os
last update of this field. This can provide an easy measure of both
I/O completion time and the backlog that may be accumulating.
+Field 12 -- # of discards completed
+ This is the total number of discards completed successfully.
+
+Field 13 -- # of discards merged
+ See the description of field 2
+
+Field 14 -- # of sectors discarded
+ This is the total number of sectors discarded successfully.
+
+Field 15 -- # of milliseconds spent discarding
+ This is the total number of milliseconds spent by all discards (as
+ measured from __make_request() to end_that_request_last()).
To avoid introducing performance bottlenecks, no locks are held while
modifying these counters. This implies that minor inaccuracies may be
diff --git a/block/genhd.c b/block/genhd.c
index 0711a800d0d4..8cc719a37b32 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1333,8 +1333,11 @@ static int diskstats_show(struct seq_file *seqf, void *v)
part_round_stats(gp->queue, cpu, hd);
part_stat_unlock();
part_in_flight(gp->queue, hd, inflight);
- seq_printf(seqf, "%4d %7d %s %lu %lu %lu "
- "%u %lu %lu %lu %u %u %u %u\n",
+ seq_printf(seqf, "%4d %7d %s "
+ "%lu %lu %lu %u "
+ "%lu %lu %lu %u "
+ "%u %u %u "
+ "%lu %lu %lu %u\n",
MAJOR(part_devt(hd)), MINOR(part_devt(hd)),
disk_name(gp, hd->partno, buf),
part_stat_read(hd, ios[STAT_READ]),
@@ -1347,7 +1350,11 @@ static int diskstats_show(struct seq_file *seqf, void *v)
jiffies_to_msecs(part_stat_read(hd, ticks[STAT_WRITE])),
inflight[0],
jiffies_to_msecs(part_stat_read(hd, io_ticks)),
- jiffies_to_msecs(part_stat_read(hd, time_in_queue))
+ jiffies_to_msecs(part_stat_read(hd, time_in_queue)),
+ part_stat_read(hd, ios[STAT_DISCARD]),
+ part_stat_read(hd, merges[STAT_DISCARD]),
+ part_stat_read(hd, sectors[STAT_DISCARD]),
+ jiffies_to_msecs(part_stat_read(hd, ticks[STAT_DISCARD]))
);
}
disk_part_iter_exit(&piter);
diff --git a/block/partition-generic.c b/block/partition-generic.c
index 0ddb06722162..5a8975a1201c 100644
--- a/block/partition-generic.c
+++ b/block/partition-generic.c
@@ -130,7 +130,8 @@ ssize_t part_stat_show(struct device *dev,
return sprintf(buf,
"%8lu %8lu %8llu %8u "
"%8lu %8lu %8llu %8u "
- "%8u %8u %8u"
+ "%8u %8u %8u "
+ "%8lu %8lu %8llu %8u"
"\n",
part_stat_read(p, ios[STAT_READ]),
part_stat_read(p, merges[STAT_READ]),
@@ -142,7 +143,11 @@ ssize_t part_stat_show(struct device *dev,
jiffies_to_msecs(part_stat_read(p, ticks[STAT_WRITE])),
inflight[0],
jiffies_to_msecs(part_stat_read(p, io_ticks)),
- jiffies_to_msecs(part_stat_read(p, time_in_queue)));
+ jiffies_to_msecs(part_stat_read(p, time_in_queue)),
+ part_stat_read(p, ios[STAT_DISCARD]),
+ part_stat_read(p, merges[STAT_DISCARD]),
+ (unsigned long long)part_stat_read(p, sectors[STAT_DISCARD]),
+ jiffies_to_msecs(part_stat_read(p, ticks[STAT_DISCARD])));
}
ssize_t part_inflight_show(struct device *dev, struct device_attribute *attr,
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 2960a96d833c..f6dfb30737d8 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -360,6 +360,7 @@ enum req_flag_bits {
enum stat_group {
STAT_READ,
STAT_WRITE,
+ STAT_DISCARD,
NR_STAT_GROUPS
};
@@ -401,8 +402,15 @@ static inline bool op_is_sync(unsigned int op)
(op & (REQ_SYNC | REQ_FUA | REQ_PREFLUSH));
}
+static inline bool op_is_discard(unsigned int op)
+{
+ return (op & REQ_OP_MASK) == REQ_OP_DISCARD;
+}
+
static inline int op_stat_group(unsigned int op)
{
+ if (op_is_discard(op))
+ return STAT_DISCARD;
return op_is_write(op);
}
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index a75445446974..57864422a2c8 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -356,7 +356,8 @@ static inline void free_part_stats(struct hd_struct *part)
#define part_stat_read_accum(part, field) \
(part_stat_read(part, field[STAT_READ]) + \
- part_stat_read(part, field[STAT_WRITE]))
+ part_stat_read(part, field[STAT_WRITE]) + \
+ part_stat_read(part, field[STAT_DISCARD]))
#define part_stat_add(cpu, part, field, addnd) do { \
__part_stat_add((cpu), (part), field, addnd); \
--
2.17.1