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| 55 | <H2><A NAME="SECTION00101410000000000000000"> |
| 56 | 8.14.1 Resource Limits</A> |
| 57 | </H2> |
| 58 | |
| 59 | <P> |
| 60 | Resources usage can be limited using the <tt class="function">setrlimit()</tt> function |
| 61 | described below. Each resource is controlled by a pair of limits: a |
| 62 | soft limit and a hard limit. The soft limit is the current limit, and |
| 63 | may be lowered or raised by a process over time. The soft limit can |
| 64 | never exceed the hard limit. The hard limit can be lowered to any |
| 65 | value greater than the soft limit, but not raised. (Only processes with |
| 66 | the effective UID of the super-user can raise a hard limit.) |
| 67 | |
| 68 | <P> |
| 69 | The specific resources that can be limited are system dependent. They |
| 70 | are described in the <span class="manpage"><i>getrlimit</i>(2)</span> man page. The resources |
| 71 | listed below are supported when the underlying operating system |
| 72 | supports them; resources which cannot be checked or controlled by the |
| 73 | operating system are not defined in this module for those platforms. |
| 74 | |
| 75 | <P> |
| 76 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 77 | <td><nobr><b><tt id='l2h-3057' xml:id='l2h-3057' class="function">getrlimit</tt></b>(</nobr></td> |
| 78 | <td><var>resource</var>)</td></tr></table></dt> |
| 79 | <dd> |
| 80 | Returns a tuple <code>(<var>soft</var>, <var>hard</var>)</code> with the current |
| 81 | soft and hard limits of <var>resource</var>. Raises <tt class="exception">ValueError</tt> if |
| 82 | an invalid resource is specified, or <tt class="exception">error</tt> if the |
| 83 | underlying system call fails unexpectedly. |
| 84 | </dl> |
| 85 | |
| 86 | <P> |
| 87 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 88 | <td><nobr><b><tt id='l2h-3058' xml:id='l2h-3058' class="function">setrlimit</tt></b>(</nobr></td> |
| 89 | <td><var>resource, limits</var>)</td></tr></table></dt> |
| 90 | <dd> |
| 91 | Sets new limits of consumption of <var>resource</var>. The <var>limits</var> |
| 92 | argument must be a tuple <code>(<var>soft</var>, <var>hard</var>)</code> of two |
| 93 | integers describing the new limits. A value of <code>-1</code> can be used to |
| 94 | specify the maximum possible upper limit. |
| 95 | |
| 96 | <P> |
| 97 | Raises <tt class="exception">ValueError</tt> if an invalid resource is specified, |
| 98 | if the new soft limit exceeds the hard limit, or if a process tries |
| 99 | to raise its hard limit (unless the process has an effective UID of |
| 100 | super-user). Can also raise <tt class="exception">error</tt> if the underlying |
| 101 | system call fails. |
| 102 | </dl> |
| 103 | |
| 104 | <P> |
| 105 | These symbols define resources whose consumption can be controlled |
| 106 | using the <tt class="function">setrlimit()</tt> and <tt class="function">getrlimit()</tt> functions |
| 107 | described below. The values of these symbols are exactly the constants |
| 108 | used by C programs. |
| 109 | |
| 110 | <P> |
| 111 | The <span class="Unix">Unix</span> man page for <span class="manpage"><i>getrlimit</i>(2)</span> lists the available |
| 112 | resources. Note that not all systems use the same symbol or same |
| 113 | value to denote the same resource. This module does not attempt to |
| 114 | mask platform differences -- symbols not defined for a platform will |
| 115 | not be available from this module on that platform. |
| 116 | |
| 117 | <P> |
| 118 | <dl><dt><b><tt id='l2h-3059' xml:id='l2h-3059'>RLIMIT_CORE</tt></b></dt> |
| 119 | <dd> |
| 120 | The maximum size (in bytes) of a core file that the current process |
| 121 | can create. This may result in the creation of a partial core file |
| 122 | if a larger core would be required to contain the entire process |
| 123 | image. |
| 124 | </dd></dl> |
| 125 | |
| 126 | <P> |
| 127 | <dl><dt><b><tt id='l2h-3060' xml:id='l2h-3060'>RLIMIT_CPU</tt></b></dt> |
| 128 | <dd> |
| 129 | The maximum amount of processor time (in seconds) that a process can |
| 130 | use. If this limit is exceeded, a <tt class="constant">SIGXCPU</tt> signal is sent to |
| 131 | the process. (See the <tt class="module"><a href="module-signal.html">signal</a></tt> module documentation for |
| 132 | information about how to catch this signal and do something useful, |
| 133 | e.g. flush open files to disk.) |
| 134 | </dd></dl> |
| 135 | |
| 136 | <P> |
| 137 | <dl><dt><b><tt id='l2h-3061' xml:id='l2h-3061'>RLIMIT_FSIZE</tt></b></dt> |
| 138 | <dd> |
| 139 | The maximum size of a file which the process may create. This only |
| 140 | affects the stack of the main thread in a multi-threaded process. |
| 141 | </dd></dl> |
| 142 | |
| 143 | <P> |
| 144 | <dl><dt><b><tt id='l2h-3062' xml:id='l2h-3062'>RLIMIT_DATA</tt></b></dt> |
| 145 | <dd> |
| 146 | The maximum size (in bytes) of the process's heap. |
| 147 | </dd></dl> |
| 148 | |
| 149 | <P> |
| 150 | <dl><dt><b><tt id='l2h-3063' xml:id='l2h-3063'>RLIMIT_STACK</tt></b></dt> |
| 151 | <dd> |
| 152 | The maximum size (in bytes) of the call stack for the current |
| 153 | process. |
| 154 | </dd></dl> |
| 155 | |
| 156 | <P> |
| 157 | <dl><dt><b><tt id='l2h-3064' xml:id='l2h-3064'>RLIMIT_RSS</tt></b></dt> |
| 158 | <dd> |
| 159 | The maximum resident set size that should be made available to the |
| 160 | process. |
| 161 | </dd></dl> |
| 162 | |
| 163 | <P> |
| 164 | <dl><dt><b><tt id='l2h-3065' xml:id='l2h-3065'>RLIMIT_NPROC</tt></b></dt> |
| 165 | <dd> |
| 166 | The maximum number of processes the current process may create. |
| 167 | </dd></dl> |
| 168 | |
| 169 | <P> |
| 170 | <dl><dt><b><tt id='l2h-3066' xml:id='l2h-3066'>RLIMIT_NOFILE</tt></b></dt> |
| 171 | <dd> |
| 172 | The maximum number of open file descriptors for the current |
| 173 | process. |
| 174 | </dd></dl> |
| 175 | |
| 176 | <P> |
| 177 | <dl><dt><b><tt id='l2h-3067' xml:id='l2h-3067'>RLIMIT_OFILE</tt></b></dt> |
| 178 | <dd> |
| 179 | The BSD name for <tt class="constant">RLIMIT_NOFILE</tt>. |
| 180 | </dd></dl> |
| 181 | |
| 182 | <P> |
| 183 | <dl><dt><b><tt id='l2h-3068' xml:id='l2h-3068'>RLIMIT_MEMLOCK</tt></b></dt> |
| 184 | <dd> |
| 185 | The maximum address space which may be locked in memory. |
| 186 | </dd></dl> |
| 187 | |
| 188 | <P> |
| 189 | <dl><dt><b><tt id='l2h-3069' xml:id='l2h-3069'>RLIMIT_VMEM</tt></b></dt> |
| 190 | <dd> |
| 191 | The largest area of mapped memory which the process may occupy. |
| 192 | </dd></dl> |
| 193 | |
| 194 | <P> |
| 195 | <dl><dt><b><tt id='l2h-3070' xml:id='l2h-3070'>RLIMIT_AS</tt></b></dt> |
| 196 | <dd> |
| 197 | The maximum area (in bytes) of address space which may be taken by |
| 198 | the process. |
| 199 | </dd></dl> |
| 200 | |
| 201 | <P> |
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