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Diffstat (limited to 'Documentation/filesystems/proc.txt')
| -rw-r--r-- | Documentation/filesystems/proc.txt | 114 |
1 files changed, 63 insertions, 51 deletions
diff --git a/Documentation/filesystems/proc.txt b/Documentation/filesystems/proc.txt index f566ad9bcb7b..bcceb99b81dd 100644 --- a/Documentation/filesystems/proc.txt +++ b/Documentation/filesystems/proc.txt @@ -923,45 +923,44 @@ CPUs. 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. +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. -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 - -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 @@ -1322,6 +1321,18 @@ debugging information is displayed on console. NMI switch that most IA32 servers have fires unknown NMI up, for example. If a system hangs up, try pressing the NMI switch. +panic_on_unrecovered_nmi +------------------------ + +The default Linux behaviour on an NMI of either memory or unknown is to continue +operation. For many environments such as scientific computing it is preferable +that the box is taken out and the error dealt with than an uncorrected +parity/ECC error get propogated. + +A small number of systems do generate NMI's for bizarre random reasons such as +power management so the default is off. That sysctl works like the existing +panic controls already in that directory. + nmi_watchdog ------------ @@ -1332,13 +1343,6 @@ determine whether or not they are still functioning properly. 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 ------ @@ -1380,15 +1384,18 @@ causes the kernel to prefer to reclaim dentries and inodes. 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 ------------------------- @@ -2408,24 +2415,29 @@ will be dumped when the <pid> process is dumped. coredump_filter is a bitmask 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. |