This patch adds document and kconfig for using of writeback feature. Signed-off-by: Minchan Kim <[email protected]> --- Documentation/ABI/testing/sysfs-block-zram | 8 ++++++++ Documentation/blockdev/zram.txt | 11 +++++++++++ drivers/block/zram/Kconfig | 12 ++++++++++++ 3 files changed, 31 insertions(+)
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram index 451b6d8..c1513c7 100644 --- a/Documentation/ABI/testing/sysfs-block-zram +++ b/Documentation/ABI/testing/sysfs-block-zram @@ -90,3 +90,11 @@ Contact: Sergey Senozhatsky <[email protected]> device's debugging info useful for kernel developers. Its format is not documented intentionally and may change anytime without any notice. + +What: /sys/block/zram<id>/backing_dev +Date: June 2017 +Contact: Minchan Kim <[email protected]> +Description: + The backing_dev file is read-write and set up backing + device for zram to write incompressible pages. + For using, user should enable CONFIG_ZRAM_WRITEBACK. diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 4fced8a..257e657 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -168,6 +168,7 @@ max_comp_streams RW the number of possible concurrent compress operations comp_algorithm RW show and change the compression algorithm compact WO trigger memory compaction debug_stat RO this file is used for zram debugging purposes +backing_dev RW set up backend storage for zram to write out User space is advised to use the following files to read the device statistics. @@ -231,5 +232,15 @@ The stat file represents device's mm statistics. It consists of a single resets the disksize to zero. You must set the disksize again before reusing the device. +* Optional Feature + += writeback + +With incompressible pages, there is no memory saving with zram. +Instead, with CONFIG_ZRAM_WRITEBACK, zram can write incompressible page +to backing storage rather than keeping it in memory. +User should set up backing device via /sys/block/zramX/backing_dev +before disksize setting. + Nitin Gupta [email protected] diff --git a/drivers/block/zram/Kconfig b/drivers/block/zram/Kconfig index b8ecba6..7cd4a8e 100644 --- a/drivers/block/zram/Kconfig +++ b/drivers/block/zram/Kconfig @@ -13,3 +13,15 @@ config ZRAM disks and maybe many more. See zram.txt for more information. + +config ZRAM_WRITEBACK + bool "Write back incompressible page to backing device" + depends on ZRAM + default n + help + With incompressible page, there is no memory saving to keep it + in memory. Instead, write it out to backing device. + For this feature, admin should set up backing device via + /sys/block/zramX/backing_dev. + + See zram.txt for more infomration. -- 2.7.4
