diff options
| author | Richard Chang <richardycc@google.com> | 2025-12-01 18:47:49 +0900 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2026-01-20 19:24:36 -0800 |
| commit | 4c1d61389e8e4307449eb2ebad997241cbf08fef (patch) | |
| tree | 1bd60c269c042a2a9c6a2eca6a8c1268b65e101d /Documentation | |
| parent | d38fab605c66778a8ddfbe2ac66c3a3eb7b2295a (diff) | |
zram: introduce writeback_compressed device attribute
Introduce witeback_compressed device attribute to toggle compressed
writeback (decompression on demand) feature.
[senozhatsky@chromium.org: rewrote original patch, added documentation]
Link: https://lkml.kernel.org/r/20251201094754.4149975-3-senozhatsky@chromium.org
Signed-off-by: Richard Chang <richardycc@google.com>
Co-developed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Stevens <stevensd@google.com>
Cc: Minchan Kim <minchan@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-block-zram | 7 | ||||
| -rw-r--r-- | Documentation/admin-guide/blockdev/zram.rst | 13 |
2 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram index 36c57de0a10a..ed10c2e4b5c2 100644 --- a/Documentation/ABI/testing/sysfs-block-zram +++ b/Documentation/ABI/testing/sysfs-block-zram @@ -150,3 +150,10 @@ Contact: Sergey Senozhatsky <senozhatsky@chromium.org> Description: The algorithm_params file is write-only and is used to setup compression algorithm parameters. + +What: /sys/block/zram<id>/writeback_compressed +Date: Decemeber 2025 +Contact: Richard Chang <richardycc@google.com> +Description: + The writeback_compressed device atrribute toggles compressed + writeback feature. diff --git a/Documentation/admin-guide/blockdev/zram.rst b/Documentation/admin-guide/blockdev/zram.rst index 3e273c1bb749..9547e4e95979 100644 --- a/Documentation/admin-guide/blockdev/zram.rst +++ b/Documentation/admin-guide/blockdev/zram.rst @@ -214,6 +214,7 @@ mem_limit WO specifies the maximum amount of memory ZRAM can writeback_limit WO specifies the maximum amount of write IO zram can write out to backing device as 4KB unit writeback_limit_enable RW show and set writeback_limit feature +writeback_compressed RW show and set compressed writeback feature comp_algorithm RW show and change the compression algorithm algorithm_params WO setup compression algorithm parameters compact WO trigger memory compaction @@ -434,6 +435,18 @@ 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. +By default zram stores written back pages in decompressed (raw) form, which +means that writeback operation involves decompression of the page before +writing it to the backing device. This behavior can be changed by enabling +`writeback_compressed` feature, which causes zram to write compressed pages +to the backing device, thus avoiding decompression overhead. To enable +this feature, execute:: + + $ echo yes > /sys/block/zramX/writeback_compressed + +Note that this feature should be configured before the `zramX` device is +initialized. + If admin wants to measure writeback count in a certain period, they could know it via /sys/block/zram0/bd_stat's 3rd column. |