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Diffstat (limited to 'drivers/staging/zram/zram.txt')
| -rw-r--r-- | drivers/staging/zram/zram.txt | 58 |
1 files changed, 36 insertions, 22 deletions
diff --git a/drivers/staging/zram/zram.txt b/drivers/staging/zram/zram.txt index 520edc1..5f75d29 100644 --- a/drivers/staging/zram/zram.txt +++ b/drivers/staging/zram/zram.txt @@ -5,33 +5,35 @@ Project home: http://compcache.googlecode.com/ * Introduction -The zram module creates RAM based block devices: /dev/ramX (X = 0, 1, ...). -Pages written to these disks are compressed and stored in memory itself. -These disks allow very fast I/O and compression provides good amounts of -memory savings. +The zram module creates RAM based block devices named /dev/zram<id> +(<id> = 0, 1, ...). Pages written to these disks are compressed and stored +in memory itself. These disks allow very fast I/O and compression provides +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. - -Individual zram devices are configured and initialized using zramconfig -userspace utility as shown in examples below. See zramconfig man page for -more details. +Statistics for individual zram devices are exported through sysfs nodes at +/sys/block/zram<id>/ * Usage Following shows a typical sequence of steps for using zram. -1) Load Modules: +1) Load Module: 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) -2) Initialize: - Use zramconfig utility to configure and initialize individual - zram devices. For example: - zramconfig /dev/zram0 --init # uses default value of disksize_kb - zramconfig /dev/zram1 --disksize_kb=102400 # 100MB /dev/zram1 +2) Set Disksize (Optional): + Set disk size by writing the value to sysfs node 'disksize' + (in bytes). If disksize is not given, default value of 25% + of RAM is used. + + # Initialize /dev/zram0 with 50MB disksize + echo $((50*1024*1024)) > /sys/block/zram0/disksize - *See zramconfig man page for more details and examples* + 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: mkswap /dev/zram0 @@ -41,17 +43,29 @@ Following shows a typical sequence of steps for using zram. mount /dev/zram1 /tmp 4) Stats: - zramconfig /dev/zram0 --stats - zramconfig /dev/zram1 --stats + Per-device statistics are exported as various nodes under + /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: swapoff /dev/zram0 umount /dev/zram1 6) Reset: - zramconfig /dev/zram0 --reset - zramconfig /dev/zram1 --reset - (This frees memory allocated for the given device). + Write any positive value to 'reset' sysfs node + echo 1 > /sys/block/zram0/reset + echo 1 > /sys/block/zram1/reset + + (This frees all the memory allocated for the given device). Please report any problems at: |
