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Subject[PATCHv3 4/7] zram: describe device attrs in documentation
Briefly describe exported device stat attrs in zram documentation.
We will eventually get rid of per-stat sysfs nodes and, thus,
clean up Documentation/ABI/testing/sysfs-block-zram file, which is
the only source of information about device sysfs nodes.

Add `num_migrated' description, since there is no independent
`num_migrated' sysfs node (and no corresponding sysfs-block-zram
entry), it will be exported via zram<id>/mm_stat file.

At this point we can provide minimal description, because
sysfs-block-zram still contains detailed information.

Acked-by: Minchan Kim <>
Signed-off-by: Sergey Senozhatsky <>
Documentation/blockdev/zram.txt | 49 +++++++++++++++++++++++++++++------------
1 file changed, 35 insertions(+), 14 deletions(-)

diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 902c97c..5d5e8be 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -117,20 +117,41 @@ execute
echo X > /sys/class/zram-control/zram_remove

8) 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
+compact WO trigger memory compaction
+File /sys/block/zram<id>/stat
+Represents block layer statistics. Read Documentation/block/stat.txt for

9) Deactivate:
swapoff /dev/zram0

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