zram: introduce per-device debug_stat sysfs node
debug_stat sysfs is read-only and represents various debugging data that
zram developers may need. This file is not meant to be used by anyone
else: its content is not documented and will change any time w/o any
notice. Therefore, the output of debug_stat file contains a version
string. To avoid any confusion, we will increase the version number
every time we modify the output.
At the moment this file exports only one value -- the number of
re-compressions, IOW, the number of times compression fast path has
failed. This stat is temporary any will be useful in case if any
per-cpu compression streams regressions will be reported.
Link: http://lkml.kernel.org/r/20160513230834.GB26763@bbox
Link: http://lkml.kernel.org/r/20160511134553.12655-1-sergey.senozhatsky@gmail.com
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 2e69e83..4518d30 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -166,3 +166,12 @@
The mm_stat file is read-only and represents device's mm
statistics (orig_data_size, compr_data_size, etc.) in a format
similar to block layer statistics file format.
+
+What: /sys/block/zram<id>/debug_stat
+Date: July 2016
+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+ The debug_stat file is read-only and represents various
+ device's debugging info useful for kernel developers. Its
+ format is not documented intentionally and may change
+ anytime without any notice.