0001 What: /sys/block/<disk>/bcache/unregister
0002 Date: November 2010
0003 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0004 Description:
0005 A write to this file causes the backing device or cache to be
0006 unregistered. If a backing device had dirty data in the cache,
0007 writeback mode is automatically disabled and all dirty data is
0008 flushed before the device is unregistered. Caches unregister
0009 all associated backing devices before unregistering themselves.
0010
0011 What: /sys/block/<disk>/bcache/clear_stats
0012 Date: November 2010
0013 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0014 Description:
0015 Writing to this file resets all the statistics for the device.
0016
0017 What: /sys/block/<disk>/bcache/cache
0018 Date: November 2010
0019 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0020 Description:
0021 For a backing device that has cache, a symlink to
0022 the bcache/ dir of that cache.
0023
0024 What: /sys/block/<disk>/bcache/cache_hits
0025 Date: November 2010
0026 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0027 Description:
0028 For backing devices: integer number of full cache hits,
0029 counted per bio. A partial cache hit counts as a miss.
0030
0031 What: /sys/block/<disk>/bcache/cache_misses
0032 Date: November 2010
0033 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0034 Description:
0035 For backing devices: integer number of cache misses.
0036
0037 What: /sys/block/<disk>/bcache/cache_hit_ratio
0038 Date: November 2010
0039 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0040 Description:
0041 For backing devices: cache hits as a percentage.
0042
0043 What: /sys/block/<disk>/bcache/sequential_cutoff
0044 Date: November 2010
0045 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0046 Description:
0047 For backing devices: Threshold past which sequential IO will
0048 skip the cache. Read and written as bytes in human readable
0049 units (i.e. echo 10M > sequntial_cutoff).
0050
0051 What: /sys/block/<disk>/bcache/bypassed
0052 Date: November 2010
0053 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0054 Description:
0055 Sum of all reads and writes that have bypassed the cache (due
0056 to the sequential cutoff). Expressed as bytes in human
0057 readable units.
0058
0059 What: /sys/block/<disk>/bcache/writeback
0060 Date: November 2010
0061 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0062 Description:
0063 For backing devices: When on, writeback caching is enabled and
0064 writes will be buffered in the cache. When off, caching is in
0065 writethrough mode; reads and writes will be added to the
0066 cache but no write buffering will take place.
0067
0068 What: /sys/block/<disk>/bcache/writeback_running
0069 Date: November 2010
0070 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0071 Description:
0072 For backing devices: when off, dirty data will not be written
0073 from the cache to the backing device. The cache will still be
0074 used to buffer writes until it is mostly full, at which point
0075 writes transparently revert to writethrough mode. Intended only
0076 for benchmarking/testing.
0077
0078 What: /sys/block/<disk>/bcache/writeback_delay
0079 Date: November 2010
0080 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0081 Description:
0082 For backing devices: In writeback mode, when dirty data is
0083 written to the cache and the cache held no dirty data for that
0084 backing device, writeback from cache to backing device starts
0085 after this delay, expressed as an integer number of seconds.
0086
0087 What: /sys/block/<disk>/bcache/writeback_percent
0088 Date: November 2010
0089 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0090 Description:
0091 For backing devices: If nonzero, writeback from cache to
0092 backing device only takes place when more than this percentage
0093 of the cache is used, allowing more write coalescing to take
0094 place and reducing total number of writes sent to the backing
0095 device. Integer between 0 and 40.
0096
0097 What: /sys/block/<disk>/bcache/synchronous
0098 Date: November 2010
0099 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0100 Description:
0101 For a cache, a boolean that allows synchronous mode to be
0102 switched on and off. In synchronous mode all writes are ordered
0103 such that the cache can reliably recover from unclean shutdown;
0104 if disabled bcache will not generally wait for writes to
0105 complete but if the cache is not shut down cleanly all data
0106 will be discarded from the cache. Should not be turned off with
0107 writeback caching enabled.
0108
0109 What: /sys/block/<disk>/bcache/discard
0110 Date: November 2010
0111 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0112 Description:
0113 For a cache, a boolean allowing discard/TRIM to be turned off
0114 or back on if the device supports it.
0115
0116 What: /sys/block/<disk>/bcache/bucket_size
0117 Date: November 2010
0118 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0119 Description:
0120 For a cache, bucket size in human readable units, as set at
0121 cache creation time; should match the erase block size of the
0122 SSD for optimal performance.
0123
0124 What: /sys/block/<disk>/bcache/nbuckets
0125 Date: November 2010
0126 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0127 Description:
0128 For a cache, the number of usable buckets.
0129
0130 What: /sys/block/<disk>/bcache/tree_depth
0131 Date: November 2010
0132 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0133 Description:
0134 For a cache, height of the btree excluding leaf nodes (i.e. a
0135 one node tree will have a depth of 0).
0136
0137 What: /sys/block/<disk>/bcache/btree_cache_size
0138 Date: November 2010
0139 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0140 Description:
0141 Number of btree buckets/nodes that are currently cached in
0142 memory; cache dynamically grows and shrinks in response to
0143 memory pressure from the rest of the system.
0144
0145 What: /sys/block/<disk>/bcache/written
0146 Date: November 2010
0147 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0148 Description:
0149 For a cache, total amount of data in human readable units
0150 written to the cache, excluding all metadata.
0151
0152 What: /sys/block/<disk>/bcache/btree_written
0153 Date: November 2010
0154 Contact: Kent Overstreet <kent.overstreet@gmail.com>
0155 Description:
0156 For a cache, sum of all btree writes in human readable units.
