[PATCH 2/4] block: add a statistic table for io sector

[Guoqing Jiang <guoqing.jiang@cloud.ionos.com>]

With the sector table, so we can know the distribution of different IO
size from upper layer, which means we could have the opportunity to tune
the performance based on the mostly issued IOs.

This change is based on our internal patch from Florian-Ewald Mueller
(florian-ewald.mueller@cloud.ionos.com).

Reviewed-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
---
 Documentation/ABI/testing/sysfs-block |  9 +++++++
 block/Kconfig                         |  3 ++-
 block/blk-core.c                      | 18 +++++++++++++
 block/genhd.c                         | 37 +++++++++++++++++++++++++++
 include/linux/part_stat.h             |  3 ++-
 5 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index 4371a0f2cb5e..0ffb63469772 100644
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -36,6 +36,15 @@ Description:
 		the statistics of I/O latency for each type (read, write,
 		discard and flush) which have happened to the disk.
 
+What:		/sys/block/<disk>/io_size
+Date:		January 2021
+Contact:	Guoqing Jiang <guoqing.jiang@cloud.ionos.com>
+Description:
+		The /sys/block/<disk>/io_size files displays the I/O
+		size of disk <disk>. With it, it is convenient to know
+		the statistics of I/O size for each type (read, write,
+		discard and flush) which have happened to the disk.
+
 What:		/sys/block/<disk>/<part>/stat
 Date:		February 2008
 Contact:	Jerome Marchand <jmarchan@redhat.com>
diff --git a/block/Kconfig b/block/Kconfig
index ca3854a7e3db..ad04ec253b09 100644
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -178,7 +178,8 @@ config BLK_ADDITIONAL_DISKSTAT
 	bool "Block layer additional diskstat"
 	default n
 	help
-	Enabling this option adds io latency statistics for each block device.
+	Enabling this option adds io latency and io size statistics for each
+	block device.
 
 	If unsure, say N.
 
diff --git a/block/blk-core.c b/block/blk-core.c
index 27cd153e374b..4271c5a8e685 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1291,12 +1291,29 @@ static void blk_additional_latency(struct block_device *part, const int sgrp,
 #endif
 }
 
+static void blk_additional_sector(struct block_device *part, const int sgrp,
+				  unsigned int sectors)
+{
+#ifdef CONFIG_BLK_ADDITIONAL_DISKSTAT
+	unsigned int idx;
+
+	if (sectors == 1)
+		idx = 0;
+	else
+		idx = ilog2(sectors);
+
+	idx = (idx > (ADD_STAT_NUM - 1)) ? (ADD_STAT_NUM - 1) : idx;
+	part_stat_inc(part, size_table[idx][sgrp]);
+#endif
+}
+
 static void blk_account_io_completion(struct request *req, unsigned int bytes)
 {
 	if (req->part && blk_do_io_stat(req)) {
 		const int sgrp = op_stat_group(req_op(req));
 
 		part_stat_lock();
+		blk_additional_sector(req->part, sgrp, bytes >> SECTOR_SHIFT);
 		part_stat_add(req->part, sectors[sgrp], bytes >> 9);
 		part_stat_unlock();
 	}
@@ -1348,6 +1365,7 @@ static unsigned long __part_start_io_acct(struct block_device *part,
 	update_io_ticks(part, now, false);
 	part_stat_inc(part, ios[sgrp]);
 	part_stat_add(part, sectors[sgrp], sectors);
+	blk_additional_sector(part, sgrp, sectors);
 	part_stat_local_inc(part, in_flight[op_is_write(op)]);
 	part_stat_unlock();
 
diff --git a/block/genhd.c b/block/genhd.c
index cdbf56f05060..5c12cf7f90a0 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -1182,6 +1182,42 @@ static ssize_t io_latency_show(struct device *dev, struct device_attribute *attr
 
 static struct device_attribute dev_attr_io_latency =
 	__ATTR(io_latency, 0444, io_latency_show, NULL);
+
+static ssize_t io_size_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct block_device *bdev = dev_to_bdev(dev);
+	size_t count = 0;
+	int i, sgrp;
+
+	for (i = 0; i < ADD_STAT_NUM; i++) {
+		unsigned int from, to;
+
+		if (i == ADD_STAT_NUM - 1) {
+			from = 2 << (i - 2);
+			count += scnprintf(buf + count, PAGE_SIZE - count,
+					   "      >=%5d   KB: ", from);
+		} else {
+			if (i < 2) {
+				from = i;
+				to = i + 1;
+			} else {
+				from = 2 << (i - 2);
+				to = 2 << (i - 1);
+			}
+			count += scnprintf(buf + count, PAGE_SIZE - count,
+					   "[%5d - %-5d) KB: ", from, to);
+		}
+		for (sgrp = 0; sgrp < NR_STAT_GROUPS; sgrp++)
+			count += scnprintf(buf + count, PAGE_SIZE - count, "%lu ",
+					   part_stat_read(bdev, size_table[i][sgrp]));
+		count += scnprintf(buf + count, PAGE_SIZE - count, "\n");
+	}
+
+	return count;
+}
+
+static struct device_attribute dev_attr_io_size =
+	__ATTR(io_size, 0444, io_size_show, NULL);
 #endif
 
 static struct attribute *disk_attrs[] = {
@@ -1205,6 +1241,7 @@ static struct attribute *disk_attrs[] = {
 #endif
 #ifdef CONFIG_BLK_ADDITIONAL_DISKSTAT
 	&dev_attr_io_latency.attr,
+	&dev_attr_io_size.attr,
 #endif
 	NULL
 };
diff --git a/include/linux/part_stat.h b/include/linux/part_stat.h
index 763953238227..8a6440ec9134 100644
--- a/include/linux/part_stat.h
+++ b/include/linux/part_stat.h
@@ -11,10 +11,11 @@ struct disk_stats {
 	unsigned long merges[NR_STAT_GROUPS];
 #ifdef CONFIG_BLK_ADDITIONAL_DISKSTAT
 	/*
-	 * We measure latency (ms) for 1, 2, ..., 1024 and >=1024.
+	 * We measure latency (ms) and size (KB) for 1, 2, ..., 1024 and >=1024.
 	 */
 #define ADD_STAT_NUM	12
 	unsigned long latency_table[ADD_STAT_NUM][NR_STAT_GROUPS];
+	unsigned long size_table[ADD_STAT_NUM][NR_STAT_GROUPS];
 #endif
 	unsigned long io_ticks;
 	local_t in_flight[2];
-- 
2.17.1