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-rw-r--r--Documentation/blockdev/zram.txt87
1 files changed, 73 insertions, 14 deletions
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