Hi Sergey,

On Tue, Aug 19, 2014 at 08:25:00PM +0900, Sergey Senozhatsky wrote:

Hello,

On (08/19/14 13:45), Chao Yu wrote:

quoted

quoted

On (08/15/14 11:27), Chao Yu wrote:

quoted

Now we have supported handling discard request which is sended by filesystem,
but no interface could be used to show information of discard.
This patch adds num_discards to stat discarded pages, then export it to sysfs
for displaying.

a side question: we account discarded pages via slot free notify in
notify_free and via req_discard in num_discards. how about accounting
both of them in num_discards? because, after all, they account a number
of discarded pages (zram_free_page()). or there any particular reason we
want to distinguish.

Yeah, I agree with you as I have no such reason unless there are our users'
explicitly requirement for showing notify_free/num_discards separately later.

How do you think of sending another patch to merge these two counts?

Minchan, what do you think? let's account discarded pages in one place.

First of all, I'd like to know why we need num_discards.
It should be in description and depends on it whether we should merge both
counts or separate.

Thanks.

quoted

One more thing is that I am missing to update document of zram, sorry about
that, let me update it in v2.

thanks.

	-ss

quoted

Thanks,
Yu

quoted

	-ss

quoted

Signed-off-by: Chao Yu <redacted>
---
 Documentation/ABI/testing/sysfs-block-zram | 10 ++++++++++
 drivers/block/zram/zram_drv.c              |  3 +++
 drivers/block/zram/zram_drv.h              |  1 +
 3 files changed, 14 insertions(+)

diff --git a/Documentation/ABI/testing/sysfs-block-zram

b/Documentation/ABI/testing/sysfs-block-zram

quoted

index 70ec992..fa8936e 100644

--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram

@@ -57,6 +57,16 @@ Description:
 		The failed_writes file is read-only and specifies the number of
 		failed writes happened on this device.

+
+What:		/sys/block/zram<id>/num_discards
+Date:		August 2014
+Contact:	Chao Yu <chao2.yu@samsung.com>
+Description:
+		The num_discards file is read-only and specifies the number of
+		physical blocks which are discarded by this device. These blocks
+		are included in discard request which is sended by filesystem as
+		the blocks are no longer used.
+
 What:		/sys/block/zram<id>/max_comp_streams
 Date:		February 2014
 Contact:	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>

diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index d00831c..904e7a5 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c

@@ -606,6 +606,7 @@ static void zram_bio_discard(struct zram *zram, u32 index,
 		bit_spin_lock(ZRAM_ACCESS, &meta->table[index].value);
 		zram_free_page(zram, index);
 		bit_spin_unlock(ZRAM_ACCESS, &meta->table[index].value);
+		atomic64_inc(&zram->stats.num_discards);
 		index++;
 		n -= PAGE_SIZE;
 	}

@@ -866,6 +867,7 @@ ZRAM_ATTR_RO(num_reads);
 ZRAM_ATTR_RO(num_writes);
 ZRAM_ATTR_RO(failed_reads);
 ZRAM_ATTR_RO(failed_writes);
+ZRAM_ATTR_RO(num_discards);
 ZRAM_ATTR_RO(invalid_io);
 ZRAM_ATTR_RO(notify_free);
 ZRAM_ATTR_RO(zero_pages);

@@ -879,6 +881,7 @@ static struct attribute *zram_disk_attrs[] = {
 	&dev_attr_num_writes.attr,
 	&dev_attr_failed_reads.attr,
 	&dev_attr_failed_writes.attr,
+	&dev_attr_num_discards.attr,
 	&dev_attr_invalid_io.attr,
 	&dev_attr_notify_free.attr,
 	&dev_attr_zero_pages.attr,

diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
index e0f725c..2994aaf 100644
--- a/drivers/block/zram/zram_drv.h
+++ b/drivers/block/zram/zram_drv.h

@@ -86,6 +86,7 @@ struct zram_stats {
 	atomic64_t num_writes;	/* --do-- */
 	atomic64_t failed_reads;	/* can happen when memory is too low */
 	atomic64_t failed_writes;	/* can happen when memory is too low */
+	atomic64_t num_discards;	/* no. of discarded pages */
 	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
 	atomic64_t notify_free;	/* no. of swap slot free notifications */
 	atomic64_t zero_pages;		/* no. of zero filled pages */
--

2.0.1.474.g72c7794

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Kind regards,
Minchan Kim

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