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author | Sergey Senozhatsky <sergey.senozhatsky@gmail.com> | 2015-04-16 01:16:09 +0200 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-04-16 01:35:21 +0200 |
commit | 8f7d282c717acaae25245c61b6b60e8995ec4ef4 (patch) | |
tree | 619cd0a9f363bfccf911f0fe2fe892a5961e9f9b /Documentation | |
parent | zram: export new 'mm_stat' sysfs attrs (diff) | |
download | linux-8f7d282c717acaae25245c61b6b60e8995ec4ef4.tar.xz linux-8f7d282c717acaae25245c61b6b60e8995ec4ef4.zip |
zram: deprecate zram attrs sysfs nodes
Add Documentation/ABI/obsolete/sysfs-block-zram file and list obsolete and
deprecated attributes there. The patch also adds additional information
to zram documentation and describes the basic strategy:
- the existing RW nodes will be downgraded to WO nodes (in 4.11)
- deprecated RO sysfs nodes will eventually be removed (in 4.11)
Users will be additionally notified about deprecated attr usage by
pr_warn_once() (added to every deprecated attr _show()), as suggested by
Minchan Kim.
User space is advised to use zram<id>/stat, zram<id>/io_stat and
zram<id>/mm_stat files.
Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reported-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/ABI/obsolete/sysfs-block-zram | 119 | ||||
-rw-r--r-- | Documentation/blockdev/zram.txt | 16 |
2 files changed, 135 insertions, 0 deletions
diff --git a/Documentation/ABI/obsolete/sysfs-block-zram b/Documentation/ABI/obsolete/sysfs-block-zram new file mode 100644 index 000000000000..720ea92cfb2e --- /dev/null +++ b/Documentation/ABI/obsolete/sysfs-block-zram @@ -0,0 +1,119 @@ +What: /sys/block/zram<id>/num_reads +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The num_reads file is read-only and specifies the number of + reads (failed or successful) done on this device. + Now accessible via zram<id>/stat node. + +What: /sys/block/zram<id>/num_writes +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The num_writes file is read-only and specifies the number of + writes (failed or successful) done on this device. + Now accessible via zram<id>/stat node. + +What: /sys/block/zram<id>/invalid_io +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The invalid_io file is read-only and specifies the number of + non-page-size-aligned I/O requests issued to this device. + Now accessible via zram<id>/io_stat node. + +What: /sys/block/zram<id>/failed_reads +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The failed_reads file is read-only and specifies the number of + failed reads happened on this device. + Now accessible via zram<id>/io_stat node. + +What: /sys/block/zram<id>/failed_writes +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The failed_writes file is read-only and specifies the number of + failed writes happened on this device. + Now accessible via zram<id>/io_stat node. + +What: /sys/block/zram<id>/notify_free +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The notify_free file is read-only. Depending on device usage + scenario it may account a) the number of pages freed because + of swap slot free notifications or b) the number of pages freed + because of REQ_DISCARD requests sent by bio. The former ones + are sent to a swap block device when a swap slot is freed, which + implies that this disk is being used as a swap disk. The latter + ones are sent by filesystem mounted with discard option, + whenever some data blocks are getting discarded. + Now accessible via zram<id>/io_stat node. + +What: /sys/block/zram<id>/zero_pages +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The zero_pages file is read-only and specifies number of zero + filled pages written to this disk. No memory is allocated for + such pages. + Now accessible via zram<id>/mm_stat node. + +What: /sys/block/zram<id>/orig_data_size +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The orig_data_size file is read-only and specifies uncompressed + size of data stored in this disk. This excludes zero-filled + pages (zero_pages) since no memory is allocated for them. + Unit: bytes + Now accessible via zram<id>/mm_stat node. + +What: /sys/block/zram<id>/compr_data_size +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The compr_data_size file is read-only and specifies compressed + size of data stored in this disk. So, compression ratio can be + calculated using orig_data_size and this statistic. + Unit: bytes + Now accessible via zram<id>/mm_stat node. + +What: /sys/block/zram<id>/mem_used_total +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The mem_used_total file is read-only and specifies the amount + of memory, including allocator fragmentation and metadata + overhead, allocated for this disk. So, allocator space + efficiency can be calculated using compr_data_size and this + statistic. + Unit: bytes + Now accessible via zram<id>/mm_stat node. + +What: /sys/block/zram<id>/mem_used_max +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The mem_used_max file is read/write and specifies the amount + of maximum memory zram have consumed to store compressed data. + For resetting the value, you should write "0". Otherwise, + you could see -EINVAL. + Unit: bytes + Downgraded to write-only node: so it's possible to set new + value only; its current value is stored in zram<id>/mm_stat + node. + +What: /sys/block/zram<id>/mem_limit +Date: August 2015 +Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com> +Description: + The mem_limit file is read/write and specifies the maximum + amount of memory ZRAM can use to store the compressed data. + The limit could be changed in run time and "0" means disable + the limit. No limit is the initial state. Unit: bytes + Downgraded to write-only node: so it's possible to set new + value only; its current value is stored in zram<id>/mm_stat + node. diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 7920f4026d36..48a183e29988 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -128,6 +128,22 @@ mem_limit RW the maximum amount of memory ZRAM can use to store 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 |