diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-fs-ext4 | 81 | ||||
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 30 | ||||
| -rw-r--r-- | Documentation/filesystems/proc.txt | 21 |
3 files changed, 108 insertions, 24 deletions
diff --git a/Documentation/ABI/testing/sysfs-fs-ext4 b/Documentation/ABI/testing/sysfs-fs-ext4 new file mode 100644 index 0000000..4e79074 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-fs-ext4 @@ -0,0 +1,81 @@ +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 +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. diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index cec829b..97882df 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -85,7 +85,7 @@ Note: More extensive information for getting started with ext4 can be * extent format more robust in face of on-disk corruption due to magics, * internal redundancy in tree * improved file allocation (multi-block alloc) -* fix 32000 subdirectory limit +* lift 32000 subdirectory limit imposed by i_links_count[1] * nsec timestamps for mtime, atime, ctime, create time * inode version field on disk (NFSv4, Lustre) * reduced e2fsck time via uninit_bg feature @@ -100,6 +100,9 @@ Note: More extensive information for getting started with ext4 can be * efficent new ordered mode in JBD2 and ext4(avoid using buffer head to force the ordering) +[1] Filesystems with a block size of 1k may see a limit imposed by the +directory hash tree having a maximum depth of two. + 2.2 Candidate features for future inclusion * Online defrag (patches available but not well tested) @@ -180,8 +183,8 @@ commit=nrsec (*) Ext4 can be told to sync all its data and metadata performance. barrier=<0|1(*)> This enables/disables the use of write barriers in - the jbd code. barrier=0 disables, barrier=1 enables. - This also requires an IO stack which can support +barrier(*) the jbd code. barrier=0 disables, barrier=1 enables. +nobarrier This also requires an IO stack which can support barriers, and if jbd gets an error on a barrier write, it will disable again with a warning. Write barriers enforce proper on-disk ordering @@ -189,6 +192,9 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in safe to use, at some performance penalty. If your disks are battery-backed in one way or another, disabling barriers may safely improve performance. + The mount options "barrier" and "nobarrier" can + also be used to enable or disable barriers, for + consistency with other ext4 mount options. inode_readahead=n This tuning parameter controls the maximum number of inode table blocks that ext4's inode @@ -310,6 +316,24 @@ journal_ioprio=prio The I/O priority (from 0 to 7, where 0 is the a slightly higher priority than the default I/O priority. +auto_da_alloc(*) Many broken applications don't use fsync() when +noauto_da_alloc replacing existing files via patterns such as + fd = open("foo.new")/write(fd,..)/close(fd)/ + rename("foo.new", "foo"), or worse yet, + fd = open("foo", O_TRUNC)/write(fd,..)/close(fd). + If auto_da_alloc is enabled, ext4 will detect + the replace-via-rename and replace-via-truncate + patterns and force that any delayed allocation + blocks are allocated such that at the next + journal commit, in the default data=ordered + mode, the data blocks of the new file are forced + to disk before the rename() operation is + commited. This provides roughly the same level + of guarantees as ext3, and avoids the + "zero-length" problem that can happen when a + system crashes before the delayed allocation + blocks are forced to disk. + Data Mode ========= There are 3 different data modes: diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index 830bad7..efc4fd9 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -940,27 +940,6 @@ Table 1-10: Files in /proc/fs/ext4/<devname> File Content mb_groups details of multiblock allocator buddy cache of free blocks mb_history multiblock allocation history - stats controls whether the multiblock allocator should start - collecting statistics, which are shown during the unmount - group_prealloc 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 - max_to_scan The maximum number of extents the multiblock allocator - will search to find the best extent - min_to_scan The minimum number of extents the multiblock allocator - will search to find the best extent - order2_req Tuning parameter which controls the minimum size for - requests (as a power of 2) where the buddy cache is - used - stream_req 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. -inode_readahead 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 .............................................................................. |
