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-rw-r--r--Documentation/blockdev/zram.txt11
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 4fced8a21307..257e65714c6a 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 @@ line of text and contains the following stats separated by whitespace:
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@vflare.org