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Staging: zram: Update zram documentation 

Update zram documentation to reflect transition form
ioctl to sysfs interface.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
This commit is contained in:
Nitin Gupta 2010-08-09 22:56:55 +05:30 committed by Greg Kroah-Hartman
parent 484875adbc
commit 9b9913d80b
1 changed files with 36 additions and 22 deletions
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58
drivers/staging/zram/zram.txt
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@ -5,33 +5,35 @@ Project home: http://compcache.googlecode.com/
* Introduction * Introduction
The zram module creates RAM based block devices: /dev/ramX (X = 0, 1, ...). The zram module creates RAM based block devices named /dev/zram<id>
Pages written to these disks are compressed and stored in memory itself. (<id> = 0, 1, ...). Pages written to these disks are compressed and stored
These disks allow very fast I/O and compression provides good amounts of in memory itself. These disks allow very fast I/O and compression provides
memory savings. good amounts of memory savings. Some of the usecases include /tmp storage,
use as swap disks, various caches under /var and maybe many more :)
See project home for use cases, performance numbers and a lot more. Statistics for individual zram devices are exported through sysfs nodes at
/sys/block/zram<id>/
Individual zram devices are configured and initialized using zramconfig
userspace utility as shown in examples below. See zramconfig man page for
more details.
* Usage * Usage
Following shows a typical sequence of steps for using zram. Following shows a typical sequence of steps for using zram.
1) Load Modules: 1) Load Module:
modprobe zram num_devices=4 modprobe zram num_devices=4
This creates 4 (uninitialized) devices: /dev/zram{0,1,2,3} This creates 4 devices: /dev/zram{0,1,2,3}
(num_devices parameter is optional. Default: 1) (num_devices parameter is optional. Default: 1)
2) Initialize: 2) Set Disksize (Optional):
Use zramconfig utility to configure and initialize individual Set disk size by writing the value to sysfs node 'disksize'
zram devices. For example: (in bytes). If disksize is not given, default value of 25%
zramconfig /dev/zram0 --init # uses default value of disksize_kb of RAM is used.
zramconfig /dev/zram1 --disksize_kb=102400 # 100MB /dev/zram1
*See zramconfig man page for more details and examples* # Initialize /dev/zram0 with 50MB disksize
echo $((50*1024*1024)) > /sys/block/zram0/disksize
NOTE: disksize cannot be changed if the disk contains any
data. So, for such a disk, you need to issue 'reset' (see below)
before you can change its disksize.
3) Activate: 3) Activate:
mkswap /dev/zram0 mkswap /dev/zram0
@ -41,17 +43,29 @@ Following shows a typical sequence of steps for using zram.
mount /dev/zram1 /tmp mount /dev/zram1 /tmp
4) Stats: 4) Stats:
zramconfig /dev/zram0 --stats Per-device statistics are exported as various nodes under
zramconfig /dev/zram1 --stats /sys/block/zram<id>/
disksize
num_reads
num_writes
invalid_io
notify_free
discard
zero_pages
orig_data_size
compr_data_size
mem_used_total
5) Deactivate: 5) Deactivate:
swapoff /dev/zram0 swapoff /dev/zram0
umount /dev/zram1 umount /dev/zram1
6) Reset: 6) Reset:
zramconfig /dev/zram0 --reset Write any positive value to 'reset' sysfs node
zramconfig /dev/zram1 --reset echo 1 > /sys/block/zram0/reset
(This frees memory allocated for the given device). echo 1 > /sys/block/zram1/reset
(This frees all the memory allocated for the given device).
Please report any problems at: Please report any problems at: