1*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_stats 2*4882a593SmuzhiyunDate: March 2008 3*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 4*4882a593SmuzhiyunDescription: 5*4882a593Smuzhiyun Controls whether the multiblock allocator should 6*4882a593Smuzhiyun collect statistics, which are shown during the unmount. 7*4882a593Smuzhiyun 1 means to collect statistics, 0 means not to collect 8*4882a593Smuzhiyun statistics 9*4882a593Smuzhiyun 10*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_group_prealloc 11*4882a593SmuzhiyunDate: March 2008 12*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 13*4882a593SmuzhiyunDescription: 14*4882a593Smuzhiyun The multiblock allocator will round up allocation 15*4882a593Smuzhiyun requests to a multiple of this tuning parameter if the 16*4882a593Smuzhiyun stripe size is not set in the ext4 superblock 17*4882a593Smuzhiyun 18*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_max_to_scan 19*4882a593SmuzhiyunDate: March 2008 20*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 21*4882a593SmuzhiyunDescription: 22*4882a593Smuzhiyun The maximum number of extents the multiblock allocator 23*4882a593Smuzhiyun will search to find the best extent 24*4882a593Smuzhiyun 25*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_min_to_scan 26*4882a593SmuzhiyunDate: March 2008 27*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 28*4882a593SmuzhiyunDescription: 29*4882a593Smuzhiyun The minimum number of extents the multiblock allocator 30*4882a593Smuzhiyun will search to find the best extent 31*4882a593Smuzhiyun 32*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_order2_req 33*4882a593SmuzhiyunDate: March 2008 34*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 35*4882a593SmuzhiyunDescription: 36*4882a593Smuzhiyun Tuning parameter which controls the minimum size for 37*4882a593Smuzhiyun requests (as a power of 2) where the buddy cache is 38*4882a593Smuzhiyun used 39*4882a593Smuzhiyun 40*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/mb_stream_req 41*4882a593SmuzhiyunDate: March 2008 42*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 43*4882a593SmuzhiyunDescription: 44*4882a593Smuzhiyun Files which have fewer blocks than this tunable 45*4882a593Smuzhiyun parameter will have their blocks allocated out of a 46*4882a593Smuzhiyun block group specific preallocation pool, so that small 47*4882a593Smuzhiyun files are packed closely together. Each large file 48*4882a593Smuzhiyun will have its blocks allocated out of its own unique 49*4882a593Smuzhiyun preallocation pool. 50*4882a593Smuzhiyun 51*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/inode_readahead_blks 52*4882a593SmuzhiyunDate: March 2008 53*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 54*4882a593SmuzhiyunDescription: 55*4882a593Smuzhiyun Tuning parameter which controls the maximum number of 56*4882a593Smuzhiyun inode table blocks that ext4's inode table readahead 57*4882a593Smuzhiyun algorithm will pre-read into the buffer cache 58*4882a593Smuzhiyun 59*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/delayed_allocation_blocks 60*4882a593SmuzhiyunDate: March 2008 61*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 62*4882a593SmuzhiyunDescription: 63*4882a593Smuzhiyun This file is read-only and shows the number of blocks 64*4882a593Smuzhiyun that are dirty in the page cache, but which do not 65*4882a593Smuzhiyun have their location in the filesystem allocated yet. 66*4882a593Smuzhiyun 67*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/lifetime_write_kbytes 68*4882a593SmuzhiyunDate: March 2008 69*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 70*4882a593SmuzhiyunDescription: 71*4882a593Smuzhiyun This file is read-only and shows the number of kilobytes 72*4882a593Smuzhiyun of data that have been written to this filesystem since it was 73*4882a593Smuzhiyun created. 74*4882a593Smuzhiyun 75*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/session_write_kbytes 76*4882a593SmuzhiyunDate: March 2008 77*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 78*4882a593SmuzhiyunDescription: 79*4882a593Smuzhiyun This file is read-only and shows the number of 80*4882a593Smuzhiyun kilobytes of data that have been written to this 81*4882a593Smuzhiyun filesystem since it was mounted. 82*4882a593Smuzhiyun 83*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/inode_goal 84*4882a593SmuzhiyunDate: June 2008 85*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 86*4882a593SmuzhiyunDescription: 87*4882a593Smuzhiyun Tuning parameter which (if non-zero) controls the goal 88*4882a593Smuzhiyun inode used by the inode allocator in preference to 89*4882a593Smuzhiyun all other allocation heuristics. This is intended for 90*4882a593Smuzhiyun debugging use only, and should be 0 on production 91*4882a593Smuzhiyun systems. 92*4882a593Smuzhiyun 93*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/max_writeback_mb_bump 94*4882a593SmuzhiyunDate: September 2009 95*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 96*4882a593SmuzhiyunDescription: 97*4882a593Smuzhiyun The maximum number of megabytes the writeback code will 98*4882a593Smuzhiyun try to write out before move on to another inode. 99*4882a593Smuzhiyun 100*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/extent_max_zeroout_kb 101*4882a593SmuzhiyunDate: August 2012 102*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 103*4882a593SmuzhiyunDescription: 104*4882a593Smuzhiyun The maximum number of kilobytes which will be zeroed 105*4882a593Smuzhiyun out in preference to creating a new uninitialized 106*4882a593Smuzhiyun extent when manipulating an inode's extent tree. Note 107*4882a593Smuzhiyun that using a larger value will increase the 108*4882a593Smuzhiyun variability of time necessary to complete a random 109*4882a593Smuzhiyun write operation (since a 4k random write might turn 110*4882a593Smuzhiyun into a much larger write due to the zeroout 111*4882a593Smuzhiyun operation). 112*4882a593Smuzhiyun 113*4882a593SmuzhiyunWhat: /sys/fs/ext4/<disk>/journal_task 114*4882a593SmuzhiyunDate: February 2019 115*4882a593SmuzhiyunContact: "Theodore Ts'o" <tytso@mit.edu> 116*4882a593SmuzhiyunDescription: 117*4882a593Smuzhiyun This file is read-only and shows the pid of journal thread in 118*4882a593Smuzhiyun current pid-namespace or 0 if task is unreachable. 119