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authorMinchan Kim <minchan@kernel.org>2018-12-28 11:36:54 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-12-28 23:11:49 +0300
commitbb416d18b850faaa44bd3bb67c9728922c3cce98 (patch)
tree112f74c2842e9e2565911546cb0ff69c407ad393 /Documentation/ABI
parent23eddf39b2c28c05cb8f8203d38e61807d701b38 (diff)
downloadlinux-bb416d18b850faaa44bd3bb67c9728922c3cce98.tar.xz
zram: writeback throttle
If there are lots of write IO with flash device, it could have a wearout problem of storage. To overcome the problem, admin needs to design write limitation to guarantee flash health for entire product life. This patch creates a new knob "writeback_limit" for zram. writeback_limit's default value is 0 so that it doesn't limit any writeback. If admin want to measure writeback count in a certain period, he could know it via /sys/block/zram0/bd_stat's 3rd column. If admin want to limit writeback as per-day 400M, he could do it like below. MB_SHIFT=20 4K_SHIFT=12 echo $((400<<MB_SHIFT>>4K_SHIFT)) > \ /sys/block/zram0/writeback_limit. If admin want to allow further write again, he could do it like below echo 0 > /sys/block/zram0/writeback_limit If admin want to see remaining writeback budget, cat /sys/block/zram0/writeback_limit The writeback_limit count will reset whenever you reset zram (e.g., system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback happened until you reset the zram to allocate extra writeback budget in next setting is user's job. [minchan@kernel.org: v4] Link: http://lkml.kernel.org/r/20181203024045.153534-8-minchan@kernel.org Link: http://lkml.kernel.org/r/20181127055429.251614-8-minchan@kernel.org Signed-off-by: Minchan Kim <minchan@kernel.org> Reviewed-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> Cc: Joey Pabalinas <joeypabalinas@gmail.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-zram9
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 65fc33b2f53b..9d2339a485c8 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -121,3 +121,12 @@ 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.
+
+What: /sys/block/zram<id>/writeback_limit
+Date: November 2018
+Contact: Minchan Kim <minchan@kernel.org>
+Description:
+ The writeback_limit file is read-write and specifies the maximum
+ amount of writeback ZRAM can do. The limit could be changed
+ in run time and "0" means disable the limit.
+ No limit is the initial state.