254 lines
8.9 KiB
Plaintext
254 lines
8.9 KiB
Plaintext
Documentation for /proc/sys/fs/* kernel version 2.2.10
|
|
(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
|
|
(c) 2009, Shen Feng<shen@cn.fujitsu.com>
|
|
|
|
For general info and legal blurb, please look in README.
|
|
|
|
==============================================================
|
|
|
|
This file contains documentation for the sysctl files in
|
|
/proc/sys/fs/ and is valid for Linux kernel version 2.2.
|
|
|
|
The files in this directory can be used to tune and monitor
|
|
miscellaneous and general things in the operation of the Linux
|
|
kernel. Since some of the files _can_ be used to screw up your
|
|
system, it is advisable to read both documentation and source
|
|
before actually making adjustments.
|
|
|
|
1. /proc/sys/fs
|
|
----------------------------------------------------------
|
|
|
|
Currently, these files are in /proc/sys/fs:
|
|
- aio-max-nr
|
|
- aio-nr
|
|
- dentry-state
|
|
- dquot-max
|
|
- dquot-nr
|
|
- file-max
|
|
- file-nr
|
|
- inode-max
|
|
- inode-nr
|
|
- inode-state
|
|
- nr_open
|
|
- overflowuid
|
|
- overflowgid
|
|
- suid_dumpable
|
|
- super-max
|
|
- super-nr
|
|
|
|
==============================================================
|
|
|
|
aio-nr & aio-max-nr:
|
|
|
|
aio-nr is the running total of the number of events specified on the
|
|
io_setup system call for all currently active aio contexts. If aio-nr
|
|
reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
|
|
raising aio-max-nr does not result in the pre-allocation or re-sizing
|
|
of any kernel data structures.
|
|
|
|
==============================================================
|
|
|
|
dentry-state:
|
|
|
|
From linux/fs/dentry.c:
|
|
--------------------------------------------------------------
|
|
struct {
|
|
int nr_dentry;
|
|
int nr_unused;
|
|
int age_limit; /* age in seconds */
|
|
int want_pages; /* pages requested by system */
|
|
int dummy[2];
|
|
} dentry_stat = {0, 0, 45, 0,};
|
|
--------------------------------------------------------------
|
|
|
|
Dentries are dynamically allocated and deallocated, and
|
|
nr_dentry seems to be 0 all the time. Hence it's safe to
|
|
assume that only nr_unused, age_limit and want_pages are
|
|
used. Nr_unused seems to be exactly what its name says.
|
|
Age_limit is the age in seconds after which dcache entries
|
|
can be reclaimed when memory is short and want_pages is
|
|
nonzero when shrink_dcache_pages() has been called and the
|
|
dcache isn't pruned yet.
|
|
|
|
==============================================================
|
|
|
|
dquot-max & dquot-nr:
|
|
|
|
The file dquot-max shows the maximum number of cached disk
|
|
quota entries.
|
|
|
|
The file dquot-nr shows the number of allocated disk quota
|
|
entries and the number of free disk quota entries.
|
|
|
|
If the number of free cached disk quotas is very low and
|
|
you have some awesome number of simultaneous system users,
|
|
you might want to raise the limit.
|
|
|
|
==============================================================
|
|
|
|
file-max & file-nr:
|
|
|
|
The kernel allocates file handles dynamically, but as yet it
|
|
doesn't free them again.
|
|
|
|
The value in file-max denotes the maximum number of file-
|
|
handles that the Linux kernel will allocate. When you get lots
|
|
of error messages about running out of file handles, you might
|
|
want to increase this limit.
|
|
|
|
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".
|
|
==============================================================
|
|
|
|
nr_open:
|
|
|
|
This denotes the maximum number of file-handles a process can
|
|
allocate. Default value is 1024*1024 (1048576) which should be
|
|
enough for most machines. Actual limit depends on RLIMIT_NOFILE
|
|
resource limit.
|
|
|
|
==============================================================
|
|
|
|
inode-max, inode-nr & inode-state:
|
|
|
|
As with file handles, the kernel allocates the inode structures
|
|
dynamically, but can't free them yet.
|
|
|
|
The value in inode-max denotes the maximum number of inode
|
|
handlers. This value should be 3-4 times larger than the value
|
|
in file-max, since stdin, stdout and network sockets also
|
|
need an inode struct to handle them. When you regularly run
|
|
out of inodes, you need to increase this value.
|
|
|
|
The file inode-nr contains the first two items from
|
|
inode-state, so we'll skip to that file...
|
|
|
|
Inode-state contains three actual numbers and four dummies.
|
|
The actual numbers are, in order of appearance, nr_inodes,
|
|
nr_free_inodes and preshrink.
|
|
|
|
Nr_inodes stands for the number of inodes the system has
|
|
allocated, this can be slightly more than inode-max because
|
|
Linux allocates them one pageful at a time.
|
|
|
|
Nr_free_inodes represents the number of free inodes (?) and
|
|
preshrink is nonzero when the nr_inodes > inode-max and the
|
|
system needs to prune the inode list instead of allocating
|
|
more.
|
|
|
|
==============================================================
|
|
|
|
overflowgid & overflowuid:
|
|
|
|
Some filesystems only support 16-bit UIDs and GIDs, although in Linux
|
|
UIDs and GIDs are 32 bits. When one of these filesystems is mounted
|
|
with writes enabled, any UID or GID that would exceed 65535 is translated
|
|
to a fixed value before being written to disk.
|
|
|
|
These sysctls allow you to change the value of the fixed UID and GID.
|
|
The default is 65534.
|
|
|
|
==============================================================
|
|
|
|
suid_dumpable:
|
|
|
|
This value can be used to query and set the core dump mode for setuid
|
|
or otherwise protected/tainted binaries. The modes are
|
|
|
|
0 - (default) - traditional behaviour. Any process which has changed
|
|
privilege levels or is execute only will not be dumped
|
|
1 - (debug) - all processes dump core when possible. The core dump is
|
|
owned by the current user and no security is applied. This is
|
|
intended for system debugging situations only. Ptrace is unchecked.
|
|
2 - (suidsafe) - any binary which normally would not be dumped is dumped
|
|
readable by root only. This allows the end user to remove
|
|
such a dump but not access it directly. For security reasons
|
|
core dumps in this mode will not overwrite one another or
|
|
other files. This mode is appropriate when administrators are
|
|
attempting to debug problems in a normal environment.
|
|
|
|
==============================================================
|
|
|
|
super-max & super-nr:
|
|
|
|
These numbers control the maximum number of superblocks, and
|
|
thus the maximum number of mounted filesystems the kernel
|
|
can have. You only need to increase super-max if you need to
|
|
mount more filesystems than the current value in super-max
|
|
allows you to.
|
|
|
|
==============================================================
|
|
|
|
aio-nr & aio-max-nr:
|
|
|
|
aio-nr shows the current system-wide number of asynchronous io
|
|
requests. aio-max-nr allows you to change the maximum value
|
|
aio-nr can grow to.
|
|
|
|
==============================================================
|
|
|
|
|
|
2. /proc/sys/fs/binfmt_misc
|
|
----------------------------------------------------------
|
|
|
|
Documentation for the files in /proc/sys/fs/binfmt_misc is
|
|
in Documentation/binfmt_misc.txt.
|
|
|
|
|
|
3. /proc/sys/fs/mqueue - POSIX message queues filesystem
|
|
----------------------------------------------------------
|
|
|
|
The "mqueue" filesystem provides the necessary kernel features to enable the
|
|
creation of a user space library that implements the POSIX message queues
|
|
API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System
|
|
Interfaces specification.)
|
|
|
|
The "mqueue" filesystem contains values for determining/setting the amount of
|
|
resources used by the file system.
|
|
|
|
/proc/sys/fs/mqueue/queues_max is a read/write file for setting/getting the
|
|
maximum number of message queues allowed on the system.
|
|
|
|
/proc/sys/fs/mqueue/msg_max is a read/write file for setting/getting the
|
|
maximum number of messages in a queue value. In fact it is the limiting value
|
|
for another (user) limit which is set in mq_open invocation. This attribute of
|
|
a queue must be less or equal then msg_max.
|
|
|
|
/proc/sys/fs/mqueue/msgsize_max is a read/write file for setting/getting the
|
|
maximum message size value (it is every message queue's attribute set during
|
|
its creation).
|
|
|
|
|
|
4. /proc/sys/fs/epoll - Configuration options for the epoll interface
|
|
--------------------------------------------------------
|
|
|
|
This directory contains configuration options for the epoll(7) interface.
|
|
|
|
max_user_instances
|
|
------------------
|
|
|
|
This is the maximum number of epoll file descriptors that a single user can
|
|
have open at a given time. The default value is 128, and should be enough
|
|
for normal users.
|
|
|
|
max_user_watches
|
|
----------------
|
|
|
|
Every epoll file descriptor can store a number of files to be monitored
|
|
for event readiness. Each one of these monitored files constitutes a "watch".
|
|
This configuration option sets the maximum number of "watches" that are
|
|
allowed for each user.
|
|
Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
|
|
on a 64bit one.
|
|
The current default value for max_user_watches is the 1/32 of the available
|
|
low memory, divided for the "watch" cost in bytes.
|
|
|