path: root/Documentation
diff options
Diffstat (limited to 'Documentation')
2 files changed, 34 insertions, 6 deletions
diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
index 8aa04684162..0da9ed6b82e 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -50,7 +50,6 @@ Description:
The failed_reads file is read-only and specifies the number of
failed reads happened on this device.
What: /sys/block/zram<id>/failed_writes
Date: February 2014
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
@@ -58,6 +57,14 @@ Description:
The failed_writes file is read-only and specifies the number of
failed writes happened on this device.
+What: /sys/block/zram<id>/max_comp_streams
+Date: February 2014
+Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
+ The max_comp_streams file is read-write and specifies the
+ number of backend's zcomp_strm compression streams (number of
+ concurrent compress operations).
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 b31ac5e5d4b..aadfe60391b 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -21,7 +21,28 @@ Following shows a typical sequence of steps for using zram.
This creates 4 devices: /dev/zram{0,1,2,3}
(num_devices parameter is optional. Default: 1)
-2) Set Disksize
+2) Set max number of compression streams
+ Compression backend may use up to max_comp_streams compression streams,
+ thus allowing up to max_comp_streams concurrent compression operations.
+ By default, compression backend uses single compression stream.
+ Examples:
+ #show max compression streams number
+ cat /sys/block/zram0/max_comp_streams
+ #set max compression streams number to 3
+ echo 3 > /sys/block/zram0/max_comp_streams
+In order to enable compression backend's multi stream support max_comp_streams
+must be initially set to desired concurrency level before ZRAM device
+initialisation. Once the device initialised as a single stream compression
+backend (max_comp_streams equals to 0) changing the value of max_comp_streams
+will not take any effect, because single stream compression backend implemented
+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
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
@@ -38,14 +59,14 @@ There is little point creating a zram of greater than twice the size of memory
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.
-3) Activate:
+4) Activate:
mkswap /dev/zram0
swapon /dev/zram0
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
-4) Stats:
+5) Stats:
Per-device statistics are exported as various nodes under
@@ -60,11 +81,11 @@ size of the disk when not in use so a huge zram is wasteful.
-5) Deactivate:
+6) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
-6) Reset:
+7) Reset:
Write any positive value to 'reset' sysfs node
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset