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| -rw-r--r-- | Documentation/blockdev/zram.txt | 44 |
1 files changed, 40 insertions, 4 deletions
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 62435bb25266..5bda5031c83d 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -14,8 +14,43 @@ Statistics for individual zram devices are exported through sysfs nodes at * Usage +There are several ways to configure and manage zram device(-s): +a) using zram and zram_control sysfs attributes +b) using zramctl utility, provided by util-linux (util-linux@vger.kernel.org). + +In this document we will describe only 'manual' zram configuration steps, +IOW, zram and zram_control sysfs attributes. + +In order to get a better idea about zramctl please consult util-linux +documentation, zramctl man-page or `zramctl --help'. Please be informed +that zram maintainers do not develop/maintain util-linux or zramctl, should +you have any questions please contact util-linux@vger.kernel.org + Following shows a typical sequence of steps for using zram. +WARNING +======= +For the sake of simplicity we skip error checking parts in most of the +examples below. However, it is your sole responsibility to handle errors. + +zram sysfs attributes always return negative values in case of errors. +The list of possible return codes: +-EBUSY -- an attempt to modify an attribute that cannot be changed once +the device has been initialised. Please reset device first; +-ENOMEM -- zram was not able to allocate enough memory to fulfil your +needs; +-EINVAL -- invalid input has been provided. + +If you use 'echo', the returned value that is changed by 'echo' utility, +and, in general case, something like: + + echo 3 > /sys/block/zram0/max_comp_streams + if [ $? -ne 0 ]; + handle_error + fi + +should suffice. + 1) Load Module: modprobe zram num_devices=4 This creates 4 devices: /dev/zram{0,1,2,3} @@ -47,7 +82,7 @@ max_comp_streams adjustment. 3) Select compression algorithm Using comp_algorithm device attribute one can see available and - currently selected (shown in square brackets) compression algortithms, + currently selected (shown in square brackets) compression algorithms, change selected compression algorithm (once the device is initialised there is no way to change compression algorithm). @@ -119,7 +154,7 @@ execute 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 +A brief description of exported device attributes. For more details please read Documentation/ABI/testing/sysfs-block-zram. Name access description @@ -140,8 +175,9 @@ zero_pages RO the number of zero filled pages written to this disk orig_data_size RO uncompressed size of data stored in this disk compr_data_size RO compressed size of data stored in this disk mem_used_total RO the amount of memory allocated for this disk -mem_used_max RW the maximum amount memory zram have consumed to - store compressed data +mem_used_max RW the maximum amount of memory zram have consumed to + store the data (to reset this counter to the actual + current value, write 1 to this attribute) mem_limit RW the maximum amount of memory ZRAM can use to store the compressed data pages_compacted RO the number of pages freed during compaction |