aboutsummaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorTheodore Ts'o <tytso@mit.edu>2008-10-09 23:21:54 -0400
committerTheodore Ts'o <tytso@mit.edu>2008-10-09 23:21:54 -0400
commit37515facd001942221d68171c81c1f46d54ffdd0 (patch)
treebd06bcb139a81167ddd3e0d28843dea3441c264e
parent5e8814f2f74f53d58aa5679bf32b38a7940033fe (diff)
ext4: Improve the documentation for ext4's /proc tunables
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> Cc: Alex Tomas <bzzz@sun.com> Cc: Andreas Dilger <adilger@sun.com>
-rw-r--r--Documentation/filesystems/proc.txt70
1 files changed, 33 insertions, 37 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt
index f566ad9bcb7b..d9ac9706735b 100644
--- a/Documentation/filesystems/proc.txt
+++ b/Documentation/filesystems/proc.txt
@@ -923,45 +923,41 @@ CPUs.
923The "procs_blocked" line gives the number of processes currently blocked, 923The "procs_blocked" line gives the number of processes currently blocked,
924waiting for I/O to complete. 924waiting for I/O to complete.
925 925
926
9261.9 Ext4 file system parameters 9271.9 Ext4 file system parameters
927------------------------------ 928------------------------------
928Ext4 file system have one directory per partition under /proc/fs/ext4/ 929
929# ls /proc/fs/ext4/hdc/ 930Information about mounted ext4 file systems can be found in
930group_prealloc max_to_scan mb_groups mb_history min_to_scan order2_req 931/proc/fs/ext4. Each mounted filesystem will have a directory in
931stats stream_req 932/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
932 933/proc/fs/ext4/dm-0). The files in each per-device directory are shown
933mb_groups: 934in Table 1-10, below.
934This file gives the details of multiblock allocator buddy cache of free blocks 935
935 936Table 1-10: Files in /proc/fs/ext4/<devname>
936mb_history: 937..............................................................................
937Multiblock allocation history. 938 File Content
938 939 mb_groups details of multiblock allocator buddy cache of free blocks
939stats: 940 mb_history multiblock allocation history
940This file indicate whether the multiblock allocator should start collecting 941 stats controls whether the multiblock allocator should start
941statistics. The statistics are shown during unmount 942 collecting statistics, which are shown during the unmount
942 943 group_prealloc the multiblock allocator will round up allocation
943group_prealloc: 944 requests to a multiple of this tuning parameter if the
944The multiblock allocator normalize the block allocation request to 945 stripe size is not set in the ext4 superblock
945group_prealloc filesystem blocks if we don't have strip value set. 946 max_to_scan The maximum number of extents the multiblock allocator
946The stripe value can be specified at mount time or during mke2fs. 947 will search to find the best extent
947 948 min_to_scan The minimum number of extents the multiblock allocator
948max_to_scan: 949 will search to find the best extent
949How long multiblock allocator can look for a best extent (in found extents) 950 order2_req Tuning parameter which controls the minimum size for
950 951 requests (as a power of 2) where the buddy cache is
951min_to_scan: 952 used
952How long multiblock allocator must look for a best extent 953 stream_req Files which have fewer blocks than this tunable
953 954 parameter will have their blocks allocated out of a
954order2_req: 955 block group specific preallocation pool, so that small
955Multiblock allocator use 2^N search using buddies only for requests greater 956 files are packed closely together. Each large file
956than or equal to order2_req. The request size is specfied in file system 957 will have its blocks allocated out of its own unique
957blocks. A value of 2 indicate only if the requests are greater than or equal 958 preallocation pool.
958to 4 blocks. 959..............................................................................
959 960
960stream_req:
961Files smaller than stream_req are served by the stream allocator, whose
962purpose is to pack requests as close each to other as possible to
963produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16
964filesystem block size will use group based preallocation.
965 961
966------------------------------------------------------------------------------ 962------------------------------------------------------------------------------
967Summary 963Summary