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-rw-r--r--Documentation/blockdev/zram.txt29
1 files changed, 24 insertions, 5 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 48a183e29988..c4de576093af 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -19,7 +19,9 @@ Following shows a typical sequence of steps for using zram.
1) Load Module:
modprobe zram num_devices=4
This creates 4 devices: /dev/zram{0,1,2,3}
- (num_devices parameter is optional. Default: 1)
+
+num_devices parameter is optional and tells zram how many devices should be
+pre-created. Default: 1.
2) Set max number of compression streams
Compression backend may use up to max_comp_streams compression streams,
@@ -97,7 +99,24 @@ size of the disk when not in use so a huge zram is wasteful.
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
-7) Stats:
+7) Add/remove zram devices
+
+zram provides a control interface, which enables dynamic (on-demand) device
+addition and removal.
+
+In order to add a new /dev/zramX device, perform read operation on hot_add
+attribute. This will return either new device's device id (meaning that you
+can use /dev/zram<id>) or error code.
+
+Example:
+ cat /sys/class/zram-control/hot_add
+ 1
+
+To remove the existing /dev/zramX device (where X is a device id)
+execute
+ echo X > /sys/class/zram-control/hot_remove
+
+8) Stats:
Per-device statistics are exported as various nodes under /sys/block/zram<id>/
A brief description of exported device attritbutes. For more details please
@@ -126,7 +145,7 @@ mem_used_max RW the maximum amount memory zram have consumed to
mem_limit RW the maximum amount of memory ZRAM can use to store
the compressed data
num_migrated RO the number of objects migrated migrated by compaction
-
+compact WO trigger memory compaction
WARNING
=======
@@ -172,11 +191,11 @@ line of text and contains the following stats separated by whitespace:
zero_pages
num_migrated
-8) Deactivate:
+9) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
-9) Reset:
+10) Reset:
Write any positive value to 'reset' sysfs node
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset