zram: make compression algorithm selection possible
Add and document `comp_algorithm' device attribute. This attribute allows
to show supported compression and currently selected compression
algorithms:
cat /sys/block/zram0/comp_algorithm
[lzo] lz4
and change selected compression algorithm:
echo lzo > /sys/block/zram0/comp_algorithm
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
(cherry picked from commit e46b8a030d76d3c94156c545c3f4c3676d813435)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index d67f0bb..2775966 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -64,6 +64,14 @@
number of backend's zcomp_strm compression streams (number of
concurrent compress operations).
+What: /sys/block/zram<id>/comp_algorithm
+Date: February 2014
+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+Description:
+ The comp_algorithm file is read-write and lets to show
+ available and selected compression algorithms, change
+ compression algorithm selection.
+
What: /sys/block/zram<id>/notify_free
Date: August 2010
Contact: Nitin Gupta <ngupta@vflare.org>
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index e82c03f..4ab2ce9 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -42,7 +42,21 @@
as a special case and does not support dynamic max_comp_streams. Only multi
stream backend supports dynamic max_comp_streams adjustment.
-3) Set Disksize
+3) Select compression algorithm
+ Using comp_algorithm device attribute one can see available and
+ currently selected (shown in square brackets) compression algortithms,
+ change selected compression algorithm (once the device is initialised
+ there is no way to change compression algorithm).
+
+ Examples:
+ #show supported compression algorithms
+ cat /sys/block/zram0/comp_algorithm
+ lzo [lz4]
+
+ #select lzo compression algorithm
+ echo lzo > /sys/block/zram0/comp_algorithm
+
+4) Set Disksize
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
Examples:
@@ -59,14 +73,14 @@
since we expect a 2:1 compression ratio. Note that zram uses about 0.1% of the
size of the disk when not in use so a huge zram is wasteful.
-4) Activate:
+5) Activate:
mkswap /dev/zram0
swapon /dev/zram0
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
-5) Stats:
+6) Stats:
Per-device statistics are exported as various nodes under
/sys/block/zram<id>/
disksize
@@ -80,11 +94,11 @@
compr_data_size
mem_used_total
-6) Deactivate:
+7) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
-7) Reset:
+8) Reset:
Write any positive value to 'reset' sysfs node
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset