diff options
| author | Minchan Kim <minchan@kernel.org> | 2018-12-28 11:36:54 +0300 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-12-28 23:11:49 +0300 |
| commit | bb416d18b850faaa44bd3bb67c9728922c3cce98 (patch) | |
| tree | 112f74c2842e9e2565911546cb0ff69c407ad393 /Documentation/ABI | |
| parent | 23eddf39b2c28c05cb8f8203d38e61807d701b38 (diff) | |
| download | linux-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-zram | 9 |
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. |