afraid it's still far from complete, but we hope it will be useful. As far as
we know, it is the first 'all-in-one' document about the /proc file system. It
is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
-SPARC, APX, etc., features, you probably won't find what you are looking for.
+SPARC, AXP, etc., features, you probably won't find what you are looking for.
It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
additions and patches are welcome and will be added to this document if you
mail them to Bodo.
process memory usage. Its seven fields are explained in Table 1-2.
-Table 1-2: Contents of the statm files
+Table 1-2: Contents of the statm files (as of 2.6.8-rc3)
..............................................................................
- File Content
- size total program size
- resident size of memory portions
- shared number of pages that are shared
- trs number of pages that are 'code'
- drs number of pages of data/stack
- lrs number of pages of library
- dt number of dirty pages
+ Field Content
+ size total program size (pages) (same as VmSize in status)
+ resident size of memory portions (pages) (same as VmRSS in status)
+ shared number of pages that are shared (i.e. backed by a file)
+ trs number of pages that are 'code' (not including libs; broken,
+ includes data segment)
+ lrs number of pages of library (always 0 on 2.6)
+ drs number of pages of data/stack (including libs; broken,
+ includes library text)
+ dt number of dirty pages (always 0 on 2.6)
..............................................................................
1.2 Kernel data
devices Available devices (block and character)
dma Used DMS channels
filesystems Supported filesystems
- driver Various drivers grouped here, currently rtc (2.4)
+ driver Various drivers grouped here, currently rtc (2.4)
execdomains Execdomains, related to security (2.4)
fb Frame Buffer devices (2.4)
fs File system parameters, currently nfs/exports (2.4)
ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
available in ZONE_NORMAL, etc...
-
-1.3 IDE devices in /proc/ide
-----------------------------
-
-The subdirectory /proc/ide contains information about all IDE devices of which
-the kernel is aware. There is one subdirectory for each IDE controller, the
-file drivers and a link for each IDE device, pointing to the device directory
-in the controller specific subtree.
-
-The file drivers contains general information about the drivers used for the
-IDE devices:
-
- > cat /proc/ide/drivers
- ide-cdrom version 4.53
- ide-disk version 1.08
-
..............................................................................
meminfo:
Writeback: 0 kB
Mapped: 280372 kB
Slab: 684068 kB
-Committed_AS: 1576424 kB
+CommitLimit: 7669796 kB
+Committed_AS: 100056 kB
PageTables: 24448 kB
-ReverseMaps: 1080904
VmallocTotal: 112216 kB
VmallocUsed: 428 kB
VmallocChunk: 111088 kB
Writeback: Memory which is actively being written back to the disk
Mapped: files which have been mmaped, such as libraries
Slab: in-kernel data structures cache
-Committed_AS: An estimate of how much RAM you would need to make a
- 99.99% guarantee that there never is OOM (out of memory)
- for this workload. Normally the kernel will overcommit
- memory. That means, say you do a 1GB malloc, nothing
- happens, really. Only when you start USING that malloc
- memory you will get real memory on demand, and just as
- much as you use. So you sort of take a mortgage and hope
- the bank doesn't go bust. Other cases might include when
- you mmap a file that's shared only when you write to it
- and you get a private copy of that data. While it normally
- is shared between processes. The Committed_AS is a
- guesstimate of how much RAM/swap you would need
- worst-case.
+ CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
+ this is the total amount of memory currently available to
+ be allocated on the system. This limit is only adhered to
+ if strict overcommit accounting is enabled (mode 2 in
+ 'vm.overcommit_memory').
+ The CommitLimit is calculated with the following formula:
+ CommitLimit = ('vm.overcommit_ratio' * Physical RAM) + Swap
+ For example, on a system with 1G of physical RAM and 7G
+ of swap with a `vm.overcommit_ratio` of 30 it would
+ yield a CommitLimit of 7.3G.
+ For more details, see the memory overcommit documentation
+ in vm/overcommit-accounting.
+Committed_AS: The amount of memory presently allocated on the system.
+ The committed memory is a sum of all of the memory which
+ has been allocated by processes, even if it has not been
+ "used" by them as of yet. A process which malloc()'s 1G
+ of memory, but only touches 300M of it will only show up
+ as using 300M of memory even if it has the address space
+ allocated for the entire 1G. This 1G is memory which has
+ been "committed" to by the VM and can be used at any time
+ by the allocating application. With strict overcommit
+ enabled on the system (mode 2 in 'vm.overcommit_memory'),
+ allocations which would exceed the CommitLimit (detailed
+ above) will not be permitted. This is useful if one needs
+ to guarantee that processes will not fail due to lack of
+ memory once that memory has been successfully allocated.
PageTables: amount of memory dedicated to the lowest level of page
tables.
- ReverseMaps: number of reverse mappings performed
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contigious block of vmalloc area which is free
+
+1.3 IDE devices in /proc/ide
+----------------------------
+
+The subdirectory /proc/ide contains information about all IDE devices of which
+the kernel is aware. There is one subdirectory for each IDE controller, the
+file drivers and a link for each IDE device, pointing to the device directory
+in the controller specific subtree.
+
+The file drivers contains general information about the drivers used for the
+IDE devices:
+
+ > cat /proc/ide/drivers
+ ide-cdrom version 4.53
+ ide-disk version 1.08
+
More detailed information can be found in the controller specific
subdirectories. These are named ide0, ide1 and so on. Each of these
directories contains the files shown in table 1-4.
The value in file-max denotes the maximum number of file handles that the
Linux kernel will allocate. When you get a lot of error messages about running
out of file handles, you might want to raise this limit. The default value is
-4096. To change it, just write the new number into the file:
+10% of RAM in kilobytes. To change it, just write the new number into the
+file:
# cat /proc/sys/fs/file-max
4096
This method of revision is useful for all customizable parameters of the
kernel - simply echo the new value to the corresponding file.
-The three values in file-nr denote the number of allocated file handles, the
-number of used file handles, and the maximum number of file handles. When the
-allocated file handles come close to the maximum, but the number of actually
-used ones is far behind, you've encountered a peak in your usage of file
-handles and you don't need to increase the maximum.
+Historically, the three values in file-nr denoted the number of allocated file
+handles, the number of allocated but unused file handles, and the maximum
+number of file handles. Linux 2.6 always reports 0 as the number of free file
+handles -- this is not an error, it just means that the number of allocated
+file handles exactly matches the number of used file handles.
+
+Attempts to allocate more file descriptors than file-max are reported with
+printk, look for "VFS: file-max limit <number> reached".
inode-state and inode-nr
------------------------
The location where the modprobe binary is located. The kernel uses this
program to load modules on demand.
+unknown_nmi_panic
+-----------------
+
+The value in this file affects behavior of handling NMI. When the value is
+non-zero, unknown NMI is trapped and then panic occurs. At that time, kernel
+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.
+
+[NOTE]
+ This function and oprofile share a NMI callback. Therefore this function
+ cannot be enabled when oprofile is activated.
+ And NMI watchdog will be disabled when the value in this file is set to
+ non-zero.
+
+
2.4 /proc/sys/vm - The virtual memory subsystem
-----------------------------------------------
The files in this directory can be used to tune the operation of the virtual
memory (VM) subsystem of the Linux kernel.
+vfs_cache_pressure
+------------------
+
+Controls the tendency of the kernel to reclaim the memory which is used for
+caching of directory and inode objects.
+
+At the default value of vfs_cache_pressure=100 the kernel will attempt to
+reclaim dentries and inodes at a "fair" rate with respect to pagecache and
+swapcache reclaim. Decreasing vfs_cache_pressure causes the kernel to prefer
+to retain dentry and inode caches. Increasing vfs_cache_pressure beyond 100
+causes the kernel to prefer to reclaim dentries and inodes.
+
dirty_background_ratio
----------------------
Data which has been dirty in-memory for longer than this interval will be
written out next time a pdflush daemon wakes up.
+legacy_va_layout
+----------------
+
+If non-zero, this sysctl disables the new 32-bit mmap mmap layout - the kernel
+will use the legacy (2.4) layout for all processes.
+
lower_zone_protection
---------------------
and thrash the system to death, so large and/or important servers will want to
set this value to 0.
+nr_hugepages and hugetlb_shm_group
+----------------------------------
+
+nr_hugepages configures number of hugetlb page reserved for the system.
+
+hugetlb_shm_group contains group id that is allowed to create SysV shared
+memory segment using hugetlb page.
+
+laptop_mode
+-----------
+
+laptop_mode is a knob that controls "laptop mode". All the things that are
+controlled by this knob are discussed in Documentation/laptop-mode.txt.
+
+block_dump
+----------
+
+block_dump enables block I/O debugging when set to a nonzero value. More
+information on block I/O debugging is in Documentation/laptop-mode.txt.
+
+swap_token_timeout
+------------------
+
+This file contains valid hold time of swap out protection token. The Linux
+VM has token based thrashing control mechanism and uses the token to prevent
+unnecessary page faults in thrashing situation. The unit of the value is
+second. The value would be useful to tune thrashing behavior.
+
2.5 /proc/sys/dev - Device specific parameters
----------------------------------------------
Writing to this file results in a flush of the routing cache.
-gc_elastic, gc_interval, gc_min_interval, gc_tresh, gc_timeout
---------------------------------------------------------------
+gc_elasticity, gc_interval, gc_min_interval_ms, gc_timeout, gc_thresh
+---------------------------------------------------------------------
Values to control the frequency and behavior of the garbage collection
-algorithm for the routing cache.
+algorithm for the routing cache. gc_min_interval is deprecated and replaced
+by gc_min_interval_ms.
+
max_size
--------
command to write value into these files, thereby changing the default settings
of the kernel.
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git://git.onelab.eu / linux-2.6.git / blobdiff