diff options
Diffstat (limited to 'Documentation/blockdev')
| -rw-r--r-- | Documentation/blockdev/nbd.txt | 48 | ||||
| -rw-r--r-- | Documentation/blockdev/zram.txt | 87 |
2 files changed, 104 insertions, 31 deletions
diff --git a/Documentation/blockdev/nbd.txt b/Documentation/blockdev/nbd.txt index 271e607304da..db242ea2bce8 100644 --- a/Documentation/blockdev/nbd.txt +++ b/Documentation/blockdev/nbd.txt @@ -1,17 +1,31 @@ - Network Block Device (TCP version) - - What is it: With this compiled in the kernel (or as a module), Linux - can use a remote server as one of its block devices. So every time - the client computer wants to read, e.g., /dev/nb0, it sends a - request over TCP to the server, which will reply with the data read. - This can be used for stations with low disk space (or even diskless) - to borrow disk space from another computer. - Unlike NFS, it is possible to put any filesystem on it, etc. - - For more information, or to download the nbd-client and nbd-server - tools, go to http://nbd.sf.net/. - - The nbd kernel module need only be installed on the client - system, as the nbd-server is completely in userspace. In fact, - the nbd-server has been successfully ported to other operating - systems, including Windows. +Network Block Device (TCP version) +================================== + +1) Overview +----------- + +What is it: With this compiled in the kernel (or as a module), Linux +can use a remote server as one of its block devices. So every time +the client computer wants to read, e.g., /dev/nb0, it sends a +request over TCP to the server, which will reply with the data read. +This can be used for stations with low disk space (or even diskless) +to borrow disk space from another computer. +Unlike NFS, it is possible to put any filesystem on it, etc. + +For more information, or to download the nbd-client and nbd-server +tools, go to http://nbd.sf.net/. + +The nbd kernel module need only be installed on the client +system, as the nbd-server is completely in userspace. In fact, +the nbd-server has been successfully ported to other operating +systems, including Windows. + +A) NBD parameters +----------------- + +max_part + Number of partitions per device (default: 0). + +nbds_max + Number of block devices that should be initialized (default: 16). + diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 7fcf9c6592ec..48a183e29988 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -98,20 +98,79 @@ size of the disk when not in use so a huge zram is wasteful. mount /dev/zram1 /tmp 7) Stats: - Per-device statistics are exported as various nodes under - /sys/block/zram<id>/ - disksize - num_reads - num_writes - failed_reads - failed_writes - invalid_io - notify_free - zero_pages - orig_data_size - compr_data_size - mem_used_total - mem_used_max +Per-device statistics are exported as various nodes under /sys/block/zram<id>/ + +A brief description of exported device attritbutes. For more details please +read Documentation/ABI/testing/sysfs-block-zram. + +Name access description +---- ------ ----------- +disksize RW show and set the device's disk size +initstate RO shows the initialization state of the device +reset WO trigger device reset +num_reads RO the number of reads +failed_reads RO the number of failed reads +num_write RO the number of writes +failed_writes RO the number of failed writes +invalid_io RO the number of non-page-size-aligned I/O requests +max_comp_streams RW the number of possible concurrent compress operations +comp_algorithm RW show and change the compression algorithm +notify_free RO the number of notifications to free pages (either + slot free notifications or REQ_DISCARD requests) +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_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 + + +WARNING +======= +per-stat sysfs attributes are considered to be deprecated. +The basic strategy is: +-- the existing RW nodes will be downgraded to WO nodes (in linux 4.11) +-- deprecated RO sysfs nodes will eventually be removed (in linux 4.11) + +The list of deprecated attributes can be found here: +Documentation/ABI/obsolete/sysfs-block-zram + +Basically, every attribute that has its own read accessible sysfs node +(e.g. num_reads) *AND* is accessible via one of the stat files (zram<id>/stat +or zram<id>/io_stat or zram<id>/mm_stat) is considered to be deprecated. + +User space is advised to use the following files to read the device statistics. + +File /sys/block/zram<id>/stat + +Represents block layer statistics. Read Documentation/block/stat.txt for +details. + +File /sys/block/zram<id>/io_stat + +The stat file represents device's I/O statistics not accounted by block +layer and, thus, not available in zram<id>/stat file. It consists of a +single line of text and contains the following stats separated by +whitespace: + failed_reads + failed_writes + invalid_io + notify_free + +File /sys/block/zram<id>/mm_stat + +The stat file represents device's mm statistics. It consists of a single +line of text and contains the following stats separated by whitespace: + orig_data_size + compr_data_size + mem_used_total + mem_limit + mem_used_max + zero_pages + num_migrated 8) Deactivate: swapoff /dev/zram0 |