The patch titled
Subject: zram: add config and doc file for writeback feature
has been added to the -mm tree. Its filename is
zram-add-config-and-doc-file-for-writeback-feature.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-add-config-and-doc-file-for-writeback-feature.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-add-config-and-doc-file-for-writeback-feature.patch
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------------------------------------------------------
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.
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
zram-clean-up-duplicated-codes-in-__zram_bvec_write.patch
zram-inlining-zram_compress.patch
zram-rename-zram_decompress_page-with-__zram_bvec_read.patch
zram-add-interface-to-specify-backing-device.patch
zram-add-free-space-management-in-backing-device.patch
zram-identify-asynchronous-ios-return-value.patch
zram-write-incompressible-pages-to-backing-device.patch
zram-read-page-from-backing-device.patch
zram-add-config-and-doc-file-for-writeback-feature.patch
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