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Diffstat (limited to 'drivers/staging/zram/zram.txt')
-rw-r--r-- | drivers/staging/zram/zram.txt | 76 |
1 files changed, 76 insertions, 0 deletions
diff --git a/drivers/staging/zram/zram.txt b/drivers/staging/zram/zram.txt new file mode 100644 index 000000000000..5f75d2987564 --- /dev/null +++ b/drivers/staging/zram/zram.txt @@ -0,0 +1,76 @@ +zram: Compressed RAM based block devices +---------------------------------------- + +Project home: http://compcache.googlecode.com/ + +* Introduction + +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 :) + +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 Module: + modprobe zram num_devices=4 + This creates 4 devices: /dev/zram{0,1,2,3} + (num_devices parameter is optional. Default: 1) + +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 + + 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 + swapon /dev/zram0 + + mkfs.ext4 /dev/zram1 + mount /dev/zram1 /tmp + +4) 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: + 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: + - Mailing list: linux-mm-cc at laptop dot org + - Issue tracker: http://code.google.com/p/compcache/issues/list + +Nitin Gupta +ngupta@vflare.org |