1 files changed, 26 insertions, 5 deletions

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index b31ac5e5d4b9..aadfe60391b7 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
+
+Note:
+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.
         Examples:
@@ -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
         /sys/block/zram<id>/
                 disksize
@@ -60,11 +81,11 @@ size of the disk when not in use so a huge zram is wasteful.
                 compr_data_size
                 mem_used_total
 
-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