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Commit b231cca438 ("message queues: increase range limits") changed
mqueue default value when attr parameter is specified NULL from hard
coded value to fs.mqueue.{msg,msgsize}_max sysctl value.
This made large side effect. When user need to use two mqueue
applications 1) using !NULL attr parameter and it require big message
size and 2) using NULL attr parameter and only need small size message,
app (1) require to raise fs.mqueue.msgsize_max and app (2) consume large
memory size even though it doesn't need.
Doug Ledford propsed to switch back it to static hard coded value.
However it also has a compatibility problem. Some applications might
started depend on the default value is tunable.
The solution is to separate default value from maximum value.
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>
Acked-by: Doug Ledford <dledford@redhat.com>
Acked-by: Joe Korty <joe.korty@ccur.com>
Cc: Amerigo Wang <amwang@redhat.com>
Acked-by: Serge E. Hallyn <serue@us.ibm.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
253 lines
9.1 KiB
Plaintext
253 lines
9.1 KiB
Plaintext
Documentation for /proc/sys/fs/* kernel version 2.2.10
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(c) 1998, 1999, Rik van Riel <riel@nl.linux.org>
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(c) 2009, Shen Feng<shen@cn.fujitsu.com>
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For general info and legal blurb, please look in README.
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==============================================================
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This file contains documentation for the sysctl files in
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/proc/sys/fs/ and is valid for Linux kernel version 2.2.
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The files in this directory can be used to tune and monitor
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miscellaneous and general things in the operation of the Linux
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kernel. Since some of the files _can_ be used to screw up your
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system, it is advisable to read both documentation and source
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before actually making adjustments.
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1. /proc/sys/fs
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----------------------------------------------------------
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Currently, these files are in /proc/sys/fs:
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- aio-max-nr
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- aio-nr
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- dentry-state
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- dquot-max
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- dquot-nr
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- file-max
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- file-nr
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- inode-max
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- inode-nr
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- inode-state
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- nr_open
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- overflowuid
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- overflowgid
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- suid_dumpable
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- super-max
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- super-nr
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==============================================================
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aio-nr & aio-max-nr:
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aio-nr is the running total of the number of events specified on the
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io_setup system call for all currently active aio contexts. If aio-nr
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reaches aio-max-nr then io_setup will fail with EAGAIN. Note that
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raising aio-max-nr does not result in the pre-allocation or re-sizing
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of any kernel data structures.
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==============================================================
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dentry-state:
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From linux/fs/dentry.c:
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--------------------------------------------------------------
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struct {
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int nr_dentry;
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int nr_unused;
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int age_limit; /* age in seconds */
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int want_pages; /* pages requested by system */
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int dummy[2];
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} dentry_stat = {0, 0, 45, 0,};
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--------------------------------------------------------------
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Dentries are dynamically allocated and deallocated, and
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nr_dentry seems to be 0 all the time. Hence it's safe to
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assume that only nr_unused, age_limit and want_pages are
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used. Nr_unused seems to be exactly what its name says.
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Age_limit is the age in seconds after which dcache entries
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can be reclaimed when memory is short and want_pages is
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nonzero when shrink_dcache_pages() has been called and the
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dcache isn't pruned yet.
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==============================================================
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dquot-max & dquot-nr:
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The file dquot-max shows the maximum number of cached disk
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quota entries.
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The file dquot-nr shows the number of allocated disk quota
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entries and the number of free disk quota entries.
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If the number of free cached disk quotas is very low and
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you have some awesome number of simultaneous system users,
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you might want to raise the limit.
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==============================================================
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file-max & file-nr:
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The value in file-max denotes the maximum number of file-
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handles that the Linux kernel will allocate. When you get lots
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of error messages about running out of file handles, you might
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want to increase this limit.
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Historically,the kernel was able to allocate file handles
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dynamically, but not to free them again. The three values in
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file-nr denote the number of allocated file handles, the number
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of allocated but unused file handles, and the maximum number of
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file handles. Linux 2.6 always reports 0 as the number of free
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file handles -- this is not an error, it just means that the
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number of allocated file handles exactly matches the number of
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used file handles.
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Attempts to allocate more file descriptors than file-max are
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reported with printk, look for "VFS: file-max limit <number>
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reached".
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==============================================================
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nr_open:
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This denotes the maximum number of file-handles a process can
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allocate. Default value is 1024*1024 (1048576) which should be
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enough for most machines. Actual limit depends on RLIMIT_NOFILE
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resource limit.
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==============================================================
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inode-max, inode-nr & inode-state:
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As with file handles, the kernel allocates the inode structures
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dynamically, but can't free them yet.
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The value in inode-max denotes the maximum number of inode
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handlers. This value should be 3-4 times larger than the value
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in file-max, since stdin, stdout and network sockets also
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need an inode struct to handle them. When you regularly run
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out of inodes, you need to increase this value.
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The file inode-nr contains the first two items from
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inode-state, so we'll skip to that file...
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Inode-state contains three actual numbers and four dummies.
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The actual numbers are, in order of appearance, nr_inodes,
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nr_free_inodes and preshrink.
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Nr_inodes stands for the number of inodes the system has
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allocated, this can be slightly more than inode-max because
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Linux allocates them one pageful at a time.
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Nr_free_inodes represents the number of free inodes (?) and
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preshrink is nonzero when the nr_inodes > inode-max and the
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system needs to prune the inode list instead of allocating
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more.
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==============================================================
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overflowgid & overflowuid:
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Some filesystems only support 16-bit UIDs and GIDs, although in Linux
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UIDs and GIDs are 32 bits. When one of these filesystems is mounted
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with writes enabled, any UID or GID that would exceed 65535 is translated
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to a fixed value before being written to disk.
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These sysctls allow you to change the value of the fixed UID and GID.
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The default is 65534.
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==============================================================
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suid_dumpable:
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This value can be used to query and set the core dump mode for setuid
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or otherwise protected/tainted binaries. The modes are
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0 - (default) - traditional behaviour. Any process which has changed
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privilege levels or is execute only will not be dumped
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1 - (debug) - all processes dump core when possible. The core dump is
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owned by the current user and no security is applied. This is
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intended for system debugging situations only. Ptrace is unchecked.
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2 - (suidsafe) - any binary which normally would not be dumped is dumped
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readable by root only. This allows the end user to remove
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such a dump but not access it directly. For security reasons
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core dumps in this mode will not overwrite one another or
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other files. This mode is appropriate when administrators are
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attempting to debug problems in a normal environment.
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==============================================================
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super-max & super-nr:
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These numbers control the maximum number of superblocks, and
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thus the maximum number of mounted filesystems the kernel
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can have. You only need to increase super-max if you need to
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mount more filesystems than the current value in super-max
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allows you to.
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==============================================================
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aio-nr & aio-max-nr:
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aio-nr shows the current system-wide number of asynchronous io
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requests. aio-max-nr allows you to change the maximum value
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aio-nr can grow to.
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==============================================================
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2. /proc/sys/fs/binfmt_misc
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----------------------------------------------------------
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Documentation for the files in /proc/sys/fs/binfmt_misc is
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in Documentation/binfmt_misc.txt.
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3. /proc/sys/fs/mqueue - POSIX message queues filesystem
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----------------------------------------------------------
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The "mqueue" filesystem provides the necessary kernel features to enable the
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creation of a user space library that implements the POSIX message queues
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API (as noted by the MSG tag in the POSIX 1003.1-2001 version of the System
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Interfaces specification.)
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The "mqueue" filesystem contains values for determining/setting the amount of
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resources used by the file system.
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/proc/sys/fs/mqueue/queues_max is a read/write file for setting/getting the
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maximum number of message queues allowed on the system.
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/proc/sys/fs/mqueue/msg_max is a read/write file for setting/getting the
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maximum number of messages in a queue value. In fact it is the limiting value
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for another (user) limit which is set in mq_open invocation. This attribute of
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a queue must be less or equal then msg_max.
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/proc/sys/fs/mqueue/msgsize_max is a read/write file for setting/getting the
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maximum message size value (it is every message queue's attribute set during
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its creation).
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/proc/sys/fs/mqueue/msg_default is a read/write file for setting/getting the
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default number of messages in a queue value if attr parameter of mq_open(2) is
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NULL. If it exceed msg_max, the default value is initialized msg_max.
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/proc/sys/fs/mqueue/msgsize_default is a read/write file for setting/getting
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the default message size value if attr parameter of mq_open(2) is NULL. If it
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exceed msgsize_max, the default value is initialized msgsize_max.
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4. /proc/sys/fs/epoll - Configuration options for the epoll interface
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--------------------------------------------------------
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This directory contains configuration options for the epoll(7) interface.
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max_user_watches
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----------------
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Every epoll file descriptor can store a number of files to be monitored
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for event readiness. Each one of these monitored files constitutes a "watch".
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This configuration option sets the maximum number of "watches" that are
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allowed for each user.
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Each "watch" costs roughly 90 bytes on a 32bit kernel, and roughly 160 bytes
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on a 64bit one.
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The current default value for max_user_watches is the 1/32 of the available
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low memory, divided for the "watch" cost in bytes.
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