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authorSergey Senozhatsky <sergey.senozhatsky@gmail.com>2014-10-09 15:29:57 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2014-10-09 22:26:03 -0400
commit015254daf1753003c19c46b90ee85a963260d270 (patch)
tree38a23db2944bfd144d2437bfe09f7c19a386dc45 /Documentation/ABI
parent461a8eee6af3b55745be64bea403ed0b743563cf (diff)
zram: use notify_free to account all free notifications
`notify_free' device attribute accounts the number of slot free notifications and internally represents the number of zram_free_page() calls. Slot free notifications are sent only when device is used as a swap device, hence `notify_free' is used only for swap devices. Since f4659d8e620d08 (zram: support REQ_DISCARD) ZRAM handles yet another one free notification (also via zram_free_page() call) -- REQ_DISCARD requests, which are sent by a filesystem, whenever some data blocks are discarded. However, there is no way to know the number of notifications in the latter case. Use `notify_free' to account the number of pages freed by zram_bio_discard() and zram_slot_free_notify(). Depending on usage scenario `notify_free' represents: a) the number of pages freed because of slot free notifications, which is equal to the number of swap_slot_free_notify() calls, so there is no behaviour change b) the number of pages freed because of REQ_DISCARD notifications Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Acked-by: Minchan Kim <minchan@kernel.org> Acked-by: Jerome Marchand <jmarchan@redhat.com> Cc: Nitin Gupta <ngupta@vflare.org> Cc: Chao Yu <chao2.yu@samsung.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation/ABI')
-rw-r--r--Documentation/ABI/testing/sysfs-block-zram13
1 files changed, 8 insertions, 5 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index b13dc993291f..a6148eaf91e5 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -77,11 +77,14 @@ What: /sys/block/zram<id>/notify_free
Date: August 2010
Contact: Nitin Gupta <ngupta@vflare.org>
Description:
- The notify_free file is read-only and specifies the number of
- swap slot free notifications received by this device. These
- notifications are sent to a swap block device when a swap slot
- is freed. This statistic is applicable only when this disk is
- being used as a swap disk.
+ The notify_free file is read-only. Depending on device usage
+ scenario it may account a) the number of pages freed because
+ of swap slot free notifications or b) the number of pages freed
+ because of REQ_DISCARD requests sent by bio. The former ones
+ are sent to a swap block device when a swap slot is freed, which
+ implies that this disk is being used as a swap disk. The latter
+ ones are sent by filesystem mounted with discard option,
+ whenever some data blocks are getting discarded.
What: /sys/block/zram<id>/zero_pages
Date: August 2010

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