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+What: /sys/fs/ext4/<disk>/mb_stats
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ Controls whether the multiblock allocator should
+ collect statistics, which are shown during the unmount.
+ 1 means to collect statistics, 0 means not to collect
+ statistics
+
+What: /sys/fs/ext4/<disk>/mb_group_prealloc
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ The multiblock allocator will round up allocation
+ requests to a multiple of this tuning parameter if the
+ stripe size is not set in the ext4 superblock
+
+What: /sys/fs/ext4/<disk>/mb_max_to_scan
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ The maximum number of extents the multiblock allocator
+ will search to find the best extent
+
+What: /sys/fs/ext4/<disk>/mb_min_to_scan
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ The minimum number of extents the multiblock allocator
+ will search to find the best extent
+
+What: /sys/fs/ext4/<disk>/mb_order2_req
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ Tuning parameter which controls the minimum size for
+ requests (as a power of 2) where the buddy cache is
+ used
+
+What: /sys/fs/ext4/<disk>/mb_stream_req
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ Files which have fewer blocks than this tunable
+ parameter will have their blocks allocated out of a
+ block group specific preallocation pool, so that small
+ files are packed closely together. Each large file
+ will have its blocks allocated out of its own unique
+ preallocation pool.
+
+What: /sys/fs/ext4/<disk>/inode_readahead_blks
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ Tuning parameter which controls the maximum number of
+ inode table blocks that ext4's inode table readahead
+ algorithm will pre-read into the buffer cache
+
+What: /sys/fs/ext4/<disk>/delayed_allocation_blocks
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ This file is read-only and shows the number of blocks
+ that are dirty in the page cache, but which do not
+ have their location in the filesystem allocated yet.
+
+What: /sys/fs/ext4/<disk>/lifetime_write_kbytes
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ This file is read-only and shows the number of kilobytes
+ of data that have been written to this filesystem since it was
+ created.
+
+What: /sys/fs/ext4/<disk>/session_write_kbytes
+Date: March 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ This file is read-only and shows the number of
+ kilobytes of data that have been written to this
+ filesystem since it was mounted.
+
+What: /sys/fs/ext4/<disk>/inode_goal
+Date: June 2008
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ Tuning parameter which (if non-zero) controls the goal
+ inode used by the inode allocator in preference to
+ all other allocation heuristics. This is intended for
+ debugging use only, and should be 0 on production
+ systems.
+
+What: /sys/fs/ext4/<disk>/max_writeback_mb_bump
+Date: September 2009
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ The maximum number of megabytes the writeback code will
+ try to write out before move on to another inode.
+
+What: /sys/fs/ext4/<disk>/extent_max_zeroout_kb
+Date: August 2012
+Contact: "Theodore Ts'o" <tytso@mit.edu>
+Description:
+ The maximum number of kilobytes which will be zeroed
+ out in preference to creating a new uninitialized
+ extent when manipulating an inode's extent tree. Note
+ that using a larger value will increase the
+ variability of time necessary to complete a random
+ write operation (since a 4k random write might turn
+ into a much larger write due to the zeroout
+ operation).