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Subject[PATCH v3 6/7] zram: add bd_stat statistics
Date
bd_stat represents things happened in backing device. Currently,
it supports bd_counts, bd_reads and bd_writes which are helpful
to understand wearout of flash and memory saving.

Signed-off-by: Minchan Kim <minchan@kernel.org>
---
Documentation/ABI/testing/sysfs-block-zram | 8 ++++++
Documentation/blockdev/zram.txt | 11 ++++++++
drivers/block/zram/zram_drv.c | 29 ++++++++++++++++++++++
drivers/block/zram/zram_drv.h | 5 ++++
4 files changed, 53 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index d1f80b077885..65fc33b2f53b 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -113,3 +113,11 @@ Contact: Minchan Kim <minchan@kernel.org>
Description:
The writeback file is write-only and trigger idle and/or
huge page writeback to backing device.
+
+What: /sys/block/zram<id>/bd_stat
+Date: November 2018
+Contact: Minchan Kim <minchan@kernel.org>
+Description:
+ The bd_stat file is read-only and represents backing device's
+ statistics (bd_count, bd_reads, bd_writes) in a format
+ similar to block layer statistics file format.
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 806cdaabac83..906df97527a7 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -221,6 +221,17 @@ The stat file represents device's mm statistics. It consists of a single
pages_compacted the number of pages freed during compaction
huge_pages the number of incompressible pages

+File /sys/block/zram<id>/bd_stat
+
+The stat file represents device's backing device statistics. It consists of
+a single line of text and contains the following stats separated by whitespace:
+ bd_count size of data written in backing device.
+ Unit: 4K bytes
+ bd_reads the number of reads from backing device
+ Unit: 4K bytes
+ bd_writes the number of writes to backing device
+ Unit: 4K bytes
+
9) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 6b5a886c8f32..67168a6ecca6 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -502,6 +502,7 @@ static unsigned long alloc_block_bdev(struct zram *zram)
if (test_and_set_bit(blk_idx, zram->bitmap))
goto retry;

+ atomic64_inc(&zram->stats.bd_count);
return blk_idx;
}

@@ -511,6 +512,7 @@ static void free_block_bdev(struct zram *zram, unsigned long blk_idx)

was_set = test_and_clear_bit(blk_idx, zram->bitmap);
WARN_ON_ONCE(!was_set);
+ atomic64_dec(&zram->stats.bd_count);
}

static void zram_page_end_io(struct bio *bio)
@@ -668,6 +670,7 @@ static ssize_t writeback_store(struct device *dev,
continue;
}

+ atomic64_inc(&zram->stats.bd_writes);
/*
* We released zram_slot_lock so need to check if the slot was
* changed. If there is freeing for the slot, we can catch it
@@ -757,6 +760,7 @@ static int read_from_bdev_sync(struct zram *zram, struct bio_vec *bvec,
static int read_from_bdev(struct zram *zram, struct bio_vec *bvec,
unsigned long entry, struct bio *parent, bool sync)
{
+ atomic64_inc(&zram->stats.bd_reads);
if (sync)
return read_from_bdev_sync(zram, bvec, entry, parent);
else
@@ -1013,6 +1017,25 @@ static ssize_t mm_stat_show(struct device *dev,
return ret;
}

+#ifdef CONFIG_ZRAM_WRITEBACK
+static ssize_t bd_stat_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ struct zram *zram = dev_to_zram(dev);
+ ssize_t ret;
+
+ down_read(&zram->init_lock);
+ ret = scnprintf(buf, PAGE_SIZE,
+ "%8llu %8llu %8llu\n",
+ (u64)atomic64_read(&zram->stats.bd_count),
+ (u64)atomic64_read(&zram->stats.bd_reads),
+ (u64)atomic64_read(&zram->stats.bd_writes));
+ up_read(&zram->init_lock);
+
+ return ret;
+}
+#endif
+
static ssize_t debug_stat_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
@@ -1033,6 +1056,9 @@ static ssize_t debug_stat_show(struct device *dev,

static DEVICE_ATTR_RO(io_stat);
static DEVICE_ATTR_RO(mm_stat);
+#ifdef CONFIG_ZRAM_WRITEBACK
+static DEVICE_ATTR_RO(bd_stat);
+#endif
static DEVICE_ATTR_RO(debug_stat);

static void zram_meta_free(struct zram *zram, u64 disksize)
@@ -1759,6 +1785,9 @@ static struct attribute *zram_disk_attrs[] = {
#endif
&dev_attr_io_stat.attr,
&dev_attr_mm_stat.attr,
+#ifdef CONFIG_ZRAM_WRITEBACK
+ &dev_attr_bd_stat.attr,
+#endif
&dev_attr_debug_stat.attr,
NULL,
};
diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index 1ad74f030b6d..bc477803530d 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h
@@ -82,6 +82,11 @@ struct zram_stats {
atomic_long_t max_used_pages; /* no. of maximum pages stored */
atomic64_t writestall; /* no. of write slow paths */
atomic64_t miss_free; /* no. of missed free */
+#ifdef CONFIG_ZRAM_WRITEBACK
+ atomic64_t bd_count; /* no. of pages in backing device */
+ atomic64_t bd_reads; /* no. of reads from backing device */
+ atomic64_t bd_writes; /* no. of writes from backing device */
+#endif
};

struct zram {
--
2.20.0.rc0.387.gc7a69e6b6c-goog
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