The "procs_blocked" line gives the number of processes currently blocked,
waiting for I/O to complete.
+
1.9 Ext4 file system parameters
------------------------------
-Ext4 file system have one directory per partition under /proc/fs/ext4/
-# ls /proc/fs/ext4/hdc/
-group_prealloc max_to_scan mb_groups mb_history min_to_scan order2_req
-stats stream_req
-
-mb_groups:
-This file gives the details of multiblock allocator buddy cache of free blocks
-
-mb_history:
-Multiblock allocation history.
-
-stats:
-This file indicate whether the multiblock allocator should start collecting
-statistics. The statistics are shown during unmount
-
-group_prealloc:
-The multiblock allocator normalize the block allocation request to
-group_prealloc filesystem blocks if we don't have strip value set.
-The stripe value can be specified at mount time or during mke2fs.
-
-max_to_scan:
-How long multiblock allocator can look for a best extent (in found extents)
-min_to_scan:
-How long multiblock allocator must look for a best extent
+Information about mounted ext4 file systems can be found in
+/proc/fs/ext4. Each mounted filesystem will have a directory in
+/proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
+/proc/fs/ext4/dm-0). The files in each per-device directory are shown
+in Table 1-10, below.
-order2_req:
-Multiblock allocator use 2^N search using buddies only for requests greater
-than or equal to order2_req. The request size is specfied in file system
-blocks. A value of 2 indicate only if the requests are greater than or equal
-to 4 blocks.
+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
+..............................................................................
-stream_req:
-Files smaller than stream_req are served by the stream allocator, whose
-purpose is to pack requests as close each to other as possible to
-produce smooth I/O traffic. Avalue of 16 indicate that file smaller than 16
-filesystem block size will use group based preallocation.
------------------------------------------------------------------------------
Summary
Because the NMI watchdog shares registers with oprofile, by disabling the NMI
watchdog, oprofile may have more registers to utilize.
-maps_protect
-------------
-
-Enables/Disables the protection of the per-process proc entries "maps" and
-"smaps". When enabled, the contents of these files are visible only to
-readers that are allowed to ptrace() the given process.
-
msgmni
------
dirty_background_ratio
----------------------
-Contains, as a percentage of total system memory, the number of pages at which
-the pdflush background writeback daemon will start writing out dirty data.
+Contains, as a percentage of the dirtyable system memory (free pages + mapped
+pages + file cache, not including locked pages and HugePages), the number of
+pages at which the pdflush background writeback daemon will start writing out
+dirty data.
dirty_ratio
-----------------
-Contains, as a percentage of total system memory, the number of pages at which
-a process which is generating disk writes will itself start writing out dirty
-data.
+Contains, as a percentage of the dirtyable system memory (free pages + mapped
+pages + file cache, not including locked pages and HugePages), the number of
+pages at which a process which is generating disk writes will itself start
+writing out dirty data.
dirty_writeback_centisecs
-------------------------
of memory types. If a bit of the bitmask is set, memory segments of the
corresponding memory type are dumped, otherwise they are not dumped.
-The following 4 memory types are supported:
+The following 7 memory types are supported:
- (bit 0) anonymous private memory
- (bit 1) anonymous shared memory
- (bit 2) file-backed private memory
- (bit 3) file-backed shared memory
- (bit 4) ELF header pages in file-backed private memory areas (it is
effective only if the bit 2 is cleared)
+ - (bit 5) hugetlb private memory
+ - (bit 6) hugetlb shared memory
Note that MMIO pages such as frame buffer are never dumped and vDSO pages
are always dumped regardless of the bitmask status.
-Default value of coredump_filter is 0x3; this means all anonymous memory
-segments are dumped.
+ Note bit 0-4 doesn't effect any hugetlb memory. hugetlb memory are only
+ effected by bit 5-6.
+
+Default value of coredump_filter is 0x23; this means all anonymous memory
+segments and hugetlb private memory are dumped.
If you don't want to dump all shared memory segments attached to pid 1234,
-write 1 to the process's proc file.
+write 0x21 to the process's proc file.
- $ echo 0x1 > /proc/1234/coredump_filter
+ $ echo 0x21 > /proc/1234/coredump_filter
When a new process is created, the process inherits the bitmask status from its
parent. It is useful to set up coredump_filter before the program runs.
projects / linux-2.6-omap-h63xx.git / blobdiff