1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
|
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.
The three values in file-nr denote the number of allocated
file handles, the number of unused file handles and the maximum
number of file handles. When the allocated file handles come
close to the maximum, but the number of unused file handles is
significantly greater than 0, you've encountered a peak in your
usage of file handles and you don't need to increase the maximum.
==============================================================
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.
|
