Resource Limits - Revision history

188.94.20.43: /* Determining the Page Size */

2013-04-16T14:06:33Z

‎Determining the Page Size

Glenn: +cat

2011-10-21T18:50:39Z

+cat

Bobnormal: add leading reference to cgroups

2010-02-18T10:12:52Z

add leading reference to cgroups

66.100.227.144: /* Determinig the Page Size */ fixed spelling

2008-07-07T00:55:35Z

‎Determinig the Page Size: fixed spelling

Bertl: typical page sizes

2007-10-12T11:03:28Z

typical page sizes

89.247.223.59: N tag is obsolete

2006-11-30T15:21:23Z

N tag is obsolete

Hollow at 23:14, 28 October 2006

2006-10-28T23:14:10Z

Hollow at 17:15, 28 October 2006

2006-10-28T17:15:37Z

Hollow at 17:00, 28 October 2006

2006-10-28T17:00:40Z

Hollow at 16:55, 28 October 2006

2006-10-28T16:55:10Z

New page

Most properties related to system resources, might it be the memory consumption, the number of processes or file-handles, qualify for imposing limits on them.

The Linux kernel provides the getrlimit and setrlimit system calls to get and set resource limits respectively. Each resource has an associated soft and hard limit. The soft limit is the value that the kernel enforces for the corresponding resource. The hard limit acts as a ceiling for the soft limit: an unprivileged process may only set its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit. A privileged process (under Linux: one with the CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit value.

The Linux-VServer kernel extends this system to provide resource limits for whole contexts, not just single processes. Additionally a few new limit types were introduced to be able to fine tune the existing limits.

Additionally the context limit system keeps track of observed maxima and resource limit hits, to provide some feedback for the administrator. See [[Context Accounting]] for details.

__FORCETOC__

== List of resource limits ==

Below is a list of resource limits used for contexts and processes within. The tables contain the following information:

; ID : Resource limit ID
; Name : Human readable identifier used in userspace utilities
; procfs : Name used in /proc/virtual/*/limit
; ulimit : command line switch for the ulimit utility
; Unit : Aprropriate unit for the limit
; Tag : Special resource limit code to denote if resources are accounted, enforced (see below)
; Description : Description of capability/flag effects

=== Special resource limit codes ===

The tag column may contain one or more of the following tags:

{| class="wikitable_inline"
! Tag
! Description
|-
| A
| Limit will be accounted
|-
| E
| Limit will be enforced
|-
| N
| The limit can be set with vlimit using its name, rather than its number
|}

=== Linux Resource Limits ===

Below is a list of resource limits available in vanilla Linux (>=2.6.18).

{| class="wikitable_list"
! ID
! Name
! procfs
! ulimit
! Tag
! Unit
! Description
|-
| 0
| CPU
| --
| -t
|
| ms
| CPU time in ms
|-
| 1
| FSIZE
| --
| -f
|
| KiB
| Maximum filesize
|-
| 2
| DATA
| --
| -d
|
| KiB
| max data size
|-
| 3
| STACK
| --
| -s
|
| KiB
| max stack size
|-
| 4
| CORE
| --
| -c
|
| KiB
| max core file size
|-
| 5
| RSS
| RSS
| -m
| AEN
| page
| max resident set size
|-
| 6
| NPROC
| PROC
| -u
| AEN
| 1
| max number of processes
|-
| 7
| NOFILE
| FILES
| -n
| AEN
| 1
| max number of open files
|-
| 8
| MEMLOCK
| VML
| -l
| AEN
| page
| max locked-in-memory address space
|-
| 9
| AS
| VM
| -v
| AEN
| page
| address space limit
|-
| 10
| LOCKS
| LOCKS
| -x
| AEN
| 1
| maximum file locks held
|-
| 11
| SIGPENDING
| --
| -i
|
| 1
| max number of pending signals
|-
| 12
| MSGQUEUE
| MSGQ
| -q
| AE
| Byte
| maximum bytes in POSIX mqueues
|-
| 13
| NICE
| --
|
|
| 1
| max nice prio allowed to raise to
|-
| 14
| RTPRIO
| --
| -r
|
| 1
| maximum realtime priority
|}

=== Linux-VServer Resource Limits ===

Below is a list of additional resource limits available in the Linux-VServer kernel.

{| class="wikitable_list"
! ID
! Name
! procfs
! Tag
! Unit
! Description
|-
| 16
| NSOCK
| SOCK
| AE
| 1
| max number of open sockets
|-
| 17
| OPENFD
| OFD
| AE
| 1
| max number of open filedescriptors
|-
| 18
| ANON
| ANON
| AE
| page
| anonymous memory limit
|-
| 19
| SHMEM
| SHM
| AE
| page
| shared memory limit
|-
| 20
| SEMARY
| SEMA
| A
| 1
| max number of semaphore arrays
|-
| 21
| NSEMS
| SEMS
| A
| 1
| max number of semaphores
|-
| 22
| DENTRY
| DENT
| AE
| 1
| max number of dentry structs
|}

== Determinig the Page Size ==

You can use the following program to determine the page size for your architecture (if it supports the getpagesize() function)

<pre>
#include <stdlib.h>
#include <stdint.h>
#include <unistd.h>

int main(int argc, char *argv[])
{
int page_size = getpagesize();
printf("The page size is %d\n", page_size);
exit(0);
}
</pre>

Here's how to compile and run it (assuming you save it as pagesize.c):

<pre>
# gcc pagesize.c -o pagesize
# ./pagesize
The page size is 4096
</pre>

'''Note''': Whether getpagesize() is present as a Linux system call depends on the architecture. If it is, it returns the kernel symbol PAGE_SIZE, which is architecture and machine model dependent. Generally, one uses binaries that are architecture but not machine model dependent, in order to have a single binary distribution per architecture. This means that a user program should not find PAGE_SIZE at compile time from a header file, but use an actual system call, at least for those architectures (like sun4) where this dependency exists. Here libc4, libc5, glibc 2.0 fail because their getpagesize() returns a statically derived value, and does not use a system call. Things are OK in glibc 2.1.

If you prefer, you can get the pagesize using python, just start a python console and write:

<pre>
>>> import resource
>>> resource.getpagesize()
4096
</pre>

== Configure Resource Limits in util-vserver ==

For example, if the adress space size (AS) and the resident set size (RSS) should be limited, the appropriate config files should be the following. You might have to create parent directories first.

<pre>
# ls -al /etc/vservers/myguest/rlimits
total 28
drwxr-xr-x 2 root root 4096 2005-08-24 12:37 .
drwxr-xr-x 5 root root 4096 2005-08-24 00:22 ..
-rw-r--r-- 1 root root 6 2005-08-24 12:43 as
-rw-r--r-- 1 root root 6 2005-08-24 12:37 rss

# cat /etc/vservers/myguest/rlimits/as
90000

# cat /etc/vservers/myguest/rlimits/rss
10000
</pre>

← Older revision		Revision as of 18:50, 21 October 2011
Line 312:		Line 312:
	10000		10000
	</pre>		</pre>
		+
		+	[[Category:Documentation]]

← Older revision		Revision as of 10:12, 18 February 2010
Line 1:		Line 1:
		+	'''NOTE: This page describes Linux <tt>rlimit</tt> support (an SVr4/BSD4.3/POSIX.1-2001 standard). vServers can also be managed using the Linux Control Group (<tt>cgroup</tt>) system, for information on Control Group based resource management, see [[util-vserver:Cgroups\|util-vserver - Cgroups]].'''
		+
	Most properties related to system resources, might it be the memory consumption, the number of processes or file-handles, qualify for imposing limits on them.		Most properties related to system resources, might it be the memory consumption, the number of processes or file-handles, qualify for imposing limits on them.

← Older revision		Revision as of 11:03, 12 October 2007
Line 266:		Line 266:
	4096		4096
	</pre>		</pre>
		+
		+	Here are some typical page sizes ...
		+
		+	{\| class="wikitable_list"
		+	! arch
		+	! pagesize
		+	\|-
		+	\| arm, extensa, s390, sh64, x86, x86_64, v850
		+	\| 4k
		+	\|-
		+	\| alpha, cris
		+	\| 8k
		+	\|-
		+	\| m68k, sparc
		+	\| 4k, 8k
		+	\|-
		+	\| powerpc
		+	\| 4k, 64k
		+	\|-
		+	\| parisc
		+	\| 4k, 16k, 64k
		+	\|-
		+	\| ia64, mips
		+	\| 4k, 8k, 16k, 64k
		+	\|}

	== Configure Resource Limits in util-vserver ==		== Configure Resource Limits in util-vserver ==

@@ Line 202: / Line 202: @@
 | ANON
 | ANON
-| AEN
+| AN
 | page
 | Maximum anonymous memory size

← Older revision		Revision as of 14:06, 16 April 2013
Line 267:		Line 267:
	>>> resource.getpagesize()		>>> resource.getpagesize()
	4096		4096
		+	</pre>
		+
		+	Most Linux operating systems also just support a simple native command
		+
		+	<pre>
		+	getconf PAGESIZE
	</pre>		</pre>

@@ Line 232: / Line 232: @@
 |}
-== Determinig the Page Size ==
+== Determining the Page Size ==
 You can use the following program to determine the page size for your architecture (if it supports the getpagesize() function)

@@ Line 34: / Line 34: @@
 | E
 | Limit will be enforced
 |}
@@ Line 152: / Line 149: @@
 | MSGQ
 | -q
-| AEN
+| AE
 | Byte
 | Maximum bytes in POSIX mqueues
@@ Line 188: / Line 185: @@
 | NSOCK
 | SOCK
-| AEN
+| AE
 | 1
 | Maximum number of open sockets
@@ Line 195: / Line 192: @@
 | OPENFD
 | OFD
-| AEN
+| AE
 | 1
 | Maximum number of open file descriptors
@@ Line 202: / Line 199: @@
 | ANON
 | ANON
-| AN
+| A
 | page
 | Maximum anonymous memory size
@@ Line 209: / Line 206: @@
 | SHMEM
 | SHM
-| AEN
+| AE
 | page
 | Maximum shared memory size
@@ Line 216: / Line 213: @@
 | SEMARY
 | SEMA
-| AN
+| A
 | 1
 | Maximum number of semaphore arrays
@@ Line 223: / Line 220: @@
 | NSEMS
 | SEMS
-| AN
+| A
 | 1
 | Maximum number of semaphores
@@ Line 230: / Line 227: @@
 | DENTRY
 | DENT
-| AEN
+| AE
 | 1
 | Maximum number of dentry structs

@@ Line 9: / Line 9: @@
 __FORCETOC__
-== List of resource limits ==
+== List of Resource Limits ==
 Below is a list of resource limits used for contexts and processes within. The tables contain the following information:
@@ Line 21: / Line 21: @@
 ; Description : Description of capability/flag effects
-=== Special resource limit codes ===
+=== Special Resource Limit Codes ===
 The tag column may contain one or more of the following tags:
@@ Line 66: / Line 66: @@
+|
 | KiB
-| Maximum filesize
+| Maximum file size
 |-
 | 2
@@ Line 74: / Line 74: @@
+|
 | KiB
-| max data size
+| Maximum size of the data segment
 |-
 | 3
@@ Line 82: / Line 82: @@
+|
 | KiB
-| max stack size
+| Maximum stack size
 |-
 | 4
@@ Line 90: / Line 90: @@
+|
 | KiB
-| max core file size
+| Maximum core file size
 |-
 | 5
@@ Line 98: / Line 98: @@
 | AE
 | page
-| max resident set size
+| Maximum resident set size
 |-
 | 6
@@ Line 106: / Line 106: @@
 | AE
 | 1
-| max number of processes
+| Maximum number of processes
 |-
 | 7
@@ Line 114: / Line 114: @@
 | AE
 | 1
-| max number of open files
+| Maximum number of open files
 |-
 | 8
@@ Line 122: / Line 122: @@
 | AE
 | page
-| max locked-in-memory address space
+| Maximum locked-in-memory address space
 |-
 | 9
@@ Line 130: / Line 130: @@
 | AE
 | page
-| address space limit
+| Maximum address space size
 |-
 | 10
@@ Line 138: / Line 138: @@
 | AE
 | 1
-| maximum file locks held
+| Maximum file locks held
 |-
 | 11
@@ Line 146: / Line 146: @@
+|
 | 1
-| max number of pending signals
+| Maximum number of pending signals
 |-
 | 12
@@ Line 154: / Line 154: @@
 | AEN
 | Byte
-| maximum bytes in POSIX mqueues
+| Maximum bytes in POSIX mqueues
 |-
 | 13
@@ Line 162: / Line 162: @@
+|
 | 1
-| max nice prio allowed to raise to
+| Maximum nice prio allowed to raise to
 |-
 | 14
@@ Line 170: / Line 170: @@
+|
 | 1
-| maximum realtime priority
+| Maximum realtime priority
 |}
@@ Line 190: / Line 190: @@
 | AEN
 | 1
-| max number of open sockets
+| Maximum number of open sockets
 |-
 | 17
@@ Line 197: / Line 197: @@
 | AEN
 | 1
-| max number of open filedescriptors
+| Maximum number of open file descriptors
 |-
 | 18
@@ Line 204: / Line 204: @@
 | AEN
 | page
-| anonymous memory limit
+| Maximum anonymous memory size
 |-
 | 19
@@ Line 211: / Line 211: @@
 | AEN
 | page
-| shared memory limit
+| Maximum shared memory size
 |-
 | 20
@@ Line 218: / Line 218: @@
 | AN
 | 1
-| max number of semaphore arrays
+| Maximum number of semaphore arrays
 |-
 | 21
@@ Line 225: / Line 225: @@
 | AN
 | 1
-| max number of semaphores
+| Maximum number of semaphores
 |-
 | 22
@@ Line 232: / Line 232: @@
 | AEN
 | 1
-| max number of dentry structs
+| Maximum number of dentry structs
 |}

@@ Line 1: / Line 1: @@
 Most properties related to system resources, might it be the memory consumption, the number of processes or file-handles, qualify for imposing limits on them.
-The Linux kernel provides the getrlimit and setrlimit system calls to get and set resource limits respectively.  Each resource has an associated soft and hard limit. The soft limit is the value that the kernel enforces for the corresponding resource.  The hard limit acts as a ceiling for the soft limit: an unprivileged process may only set its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit.  A privileged process (under Linux: one with the CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit value.
+The Linux kernel provides the getrlimit and setrlimit system calls to get and set resource limits ''per process''.  Each resource has an associated soft and hard limit. The soft limit is the value that the kernel enforces for the corresponding resource.  The hard limit acts as a ceiling for the soft limit: an unprivileged process may only set its soft limit to a value in the range from 0 up to the hard limit, and (irreversibly) lower its hard limit.  A privileged process (one with the CAP_SYS_RESOURCE capability) may make arbitrary changes to either limit value.
-The Linux-VServer kernel extends this system to provide resource limits for whole contexts, not just single processes. Additionally a few new limit types were introduced to be able to fine tune the existing limits.
+The Linux-VServer kernel extends this system to provide resource limits for ''whole contexts'', not just single processes. Additionally a few new limit types missing in the vanilla kernel were introduced.
 Additionally the context limit system keeps track of observed maxima and resource limit hits, to provide some feedback for the administrator. See [[Context Accounting]] for details.
@@ Line 36: / Line 36: @@
 |-
 | N
-| The limit can be set with vlimit using its name, rather than its number
+| The limit cannot be set with vlimit using its name. Use its number instead.
 |}
@@ Line 96: / Line 96: @@
 | RSS
 | -m
-| AEN
+| AE
 | page
 | max resident set size
@@ Line 104: / Line 104: @@
 | PROC
 | -u
-| AEN
+| AE
 | 1
 | max number of processes
@@ Line 112: / Line 112: @@
 | FILES
 | -n
-| AEN
+| AE
 | 1
 | max number of open files
@@ Line 120: / Line 120: @@
 | VML
 | -l
-| AEN
+| AE
 | page
 | max locked-in-memory address space
@@ Line 128: / Line 128: @@
 | VM
 | -v
-| AEN
+| AE
 | page
 | address space limit
@@ Line 136: / Line 136: @@
 | LOCKS
 | -x
-| AEN
+| AE
 | 1
 | maximum file locks held
@@ Line 152: / Line 152: @@
 | MSGQ
 | -q
-| AE
+| AEN
 | Byte
 | maximum bytes in POSIX mqueues
@@ Line 188: / Line 188: @@
 | NSOCK
 | SOCK
-| AE
+| AEN
 | 1
 | max number of open sockets
@@ Line 195: / Line 195: @@
 | OPENFD
 | OFD
-| AE
+| AEN
 | 1
 | max number of open filedescriptors
@@ Line 202: / Line 202: @@
 | ANON
 | ANON
-| AE
+| AEN
 | page
 | anonymous memory limit
@@ Line 209: / Line 209: @@
 | SHMEM
 | SHM
-| AE
+| AEN
 | page
 | shared memory limit
@@ Line 216: / Line 216: @@
 | SEMARY
 | SEMA
-| A
+| AN
 | 1
 | max number of semaphore arrays
@@ Line 223: / Line 223: @@
 | NSEMS
 | SEMS
-| A
+| AN
 | 1
 | max number of semaphores
@@ Line 230: / Line 230: @@
 | DENTRY
 | DENT
-| AE
+| AEN
 | 1
 | max number of dentry structs