From: Minchan Kim <minchan@xxxxxxxxxx> Subject: zram: add config and doc file for writeback feature This patch adds document and kconfig for using of writeback feature. Link: http://lkml.kernel.org/r/1498459987-24562-10-git-send-email-minchan@xxxxxxxxxx Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> Cc: Juneho Choi <juno.choi@xxxxxxx> Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- Documentation/ABI/testing/sysfs-block-zram | 8 ++++++++ Documentation/blockdev/zram.txt | 11 +++++++++++ drivers/block/zram/Kconfig | 12 ++++++++++++ 3 files changed, 31 insertions(+) diff -puN Documentation/ABI/testing/sysfs-block-zram~zram-add-config-and-doc-file-for-writeback-feature Documentation/ABI/testing/sysfs-block-zram --- a/Documentation/ABI/testing/sysfs-block-zram~zram-add-config-and-doc-file-for-writeback-feature +++ a/Documentation/ABI/testing/sysfs-block-zram @@ -90,3 +90,11 @@ Description: 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 <minchan@xxxxxxxxxx> +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 -puN Documentation/blockdev/zram.txt~zram-add-config-and-doc-file-for-writeback-feature Documentation/blockdev/zram.txt --- a/Documentation/blockdev/zram.txt~zram-add-config-and-doc-file-for-writeback-feature +++ a/Documentation/blockdev/zram.txt @@ -168,6 +168,7 @@ max_comp_streams RW the number of po 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 @@ line of text and contains the following 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 ngupta@xxxxxxxxxx diff -puN drivers/block/zram/Kconfig~zram-add-config-and-doc-file-for-writeback-feature drivers/block/zram/Kconfig --- a/drivers/block/zram/Kconfig~zram-add-config-and-doc-file-for-writeback-feature +++ a/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. _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
