1:mod:`resource` --- Resource usage information 2============================================== 3 4.. module:: resource 5 :platform: Unix 6 :synopsis: An interface to provide resource usage information on the current process. 7 8.. moduleauthor:: Jeremy Hylton <jeremy@alum.mit.edu> 9.. sectionauthor:: Jeremy Hylton <jeremy@alum.mit.edu> 10 11-------------- 12 13This module provides basic mechanisms for measuring and controlling system 14resources utilized by a program. 15 16Symbolic constants are used to specify particular system resources and to 17request usage information about either the current process or its children. 18 19An :exc:`OSError` is raised on syscall failure. 20 21 22.. exception:: error 23 24 A deprecated alias of :exc:`OSError`. 25 26 .. versionchanged:: 3.3 27 Following :pep:`3151`, this class was made an alias of :exc:`OSError`. 28 29 30Resource Limits 31--------------- 32 33Resources usage can be limited using the :func:`setrlimit` function described 34below. Each resource is controlled by a pair of limits: a soft limit and a hard 35limit. The soft limit is the current limit, and may be lowered or raised by a 36process over time. The soft limit can never exceed the hard limit. The hard 37limit can be lowered to any value greater than the soft limit, but not raised. 38(Only processes with the effective UID of the super-user can raise a hard 39limit.) 40 41The specific resources that can be limited are system dependent. They are 42described in the :manpage:`getrlimit(2)` man page. The resources listed below 43are supported when the underlying operating system supports them; resources 44which cannot be checked or controlled by the operating system are not defined in 45this module for those platforms. 46 47 48.. data:: RLIM_INFINITY 49 50 Constant used to represent the limit for an unlimited resource. 51 52 53.. function:: getrlimit(resource) 54 55 Returns a tuple ``(soft, hard)`` with the current soft and hard limits of 56 *resource*. Raises :exc:`ValueError` if an invalid resource is specified, or 57 :exc:`error` if the underlying system call fails unexpectedly. 58 59 60.. function:: setrlimit(resource, limits) 61 62 Sets new limits of consumption of *resource*. The *limits* argument must be a 63 tuple ``(soft, hard)`` of two integers describing the new limits. A value of 64 :data:`~resource.RLIM_INFINITY` can be used to request a limit that is 65 unlimited. 66 67 Raises :exc:`ValueError` if an invalid resource is specified, if the new soft 68 limit exceeds the hard limit, or if a process tries to raise its hard limit. 69 Specifying a limit of :data:`~resource.RLIM_INFINITY` when the hard or 70 system limit for that resource is not unlimited will result in a 71 :exc:`ValueError`. A process with the effective UID of super-user can 72 request any valid limit value, including unlimited, but :exc:`ValueError` 73 will still be raised if the requested limit exceeds the system imposed 74 limit. 75 76 ``setrlimit`` may also raise :exc:`error` if the underlying system call 77 fails. 78 79 VxWorks only supports setting :data:`RLIMIT_NOFILE`. 80 81 .. audit-event:: resource.setrlimit resource,limits resource.setrlimit 82 83 84.. function:: prlimit(pid, resource[, limits]) 85 86 Combines :func:`setrlimit` and :func:`getrlimit` in one function and 87 supports to get and set the resources limits of an arbitrary process. If 88 *pid* is 0, then the call applies to the current process. *resource* and 89 *limits* have the same meaning as in :func:`setrlimit`, except that 90 *limits* is optional. 91 92 When *limits* is not given the function returns the *resource* limit of the 93 process *pid*. When *limits* is given the *resource* limit of the process is 94 set and the former resource limit is returned. 95 96 Raises :exc:`ProcessLookupError` when *pid* can't be found and 97 :exc:`PermissionError` when the user doesn't have ``CAP_SYS_RESOURCE`` for 98 the process. 99 100 .. audit-event:: resource.prlimit pid,resource,limits resource.prlimit 101 102 .. availability:: Linux 2.6.36 or later with glibc 2.13 or later. 103 104 .. versionadded:: 3.4 105 106 107These symbols define resources whose consumption can be controlled using the 108:func:`setrlimit` and :func:`getrlimit` functions described below. The values of 109these symbols are exactly the constants used by C programs. 110 111The Unix man page for :manpage:`getrlimit(2)` lists the available resources. 112Note that not all systems use the same symbol or same value to denote the same 113resource. This module does not attempt to mask platform differences --- symbols 114not defined for a platform will not be available from this module on that 115platform. 116 117 118.. data:: RLIMIT_CORE 119 120 The maximum size (in bytes) of a core file that the current process can create. 121 This may result in the creation of a partial core file if a larger core would be 122 required to contain the entire process image. 123 124 125.. data:: RLIMIT_CPU 126 127 The maximum amount of processor time (in seconds) that a process can use. If 128 this limit is exceeded, a :const:`SIGXCPU` signal is sent to the process. (See 129 the :mod:`signal` module documentation for information about how to catch this 130 signal and do something useful, e.g. flush open files to disk.) 131 132 133.. data:: RLIMIT_FSIZE 134 135 The maximum size of a file which the process may create. 136 137 138.. data:: RLIMIT_DATA 139 140 The maximum size (in bytes) of the process's heap. 141 142 143.. data:: RLIMIT_STACK 144 145 The maximum size (in bytes) of the call stack for the current process. This only 146 affects the stack of the main thread in a multi-threaded process. 147 148 149.. data:: RLIMIT_RSS 150 151 The maximum resident set size that should be made available to the process. 152 153 154.. data:: RLIMIT_NPROC 155 156 The maximum number of processes the current process may create. 157 158 159.. data:: RLIMIT_NOFILE 160 161 The maximum number of open file descriptors for the current process. 162 163 164.. data:: RLIMIT_OFILE 165 166 The BSD name for :const:`RLIMIT_NOFILE`. 167 168 169.. data:: RLIMIT_MEMLOCK 170 171 The maximum address space which may be locked in memory. 172 173 174.. data:: RLIMIT_VMEM 175 176 The largest area of mapped memory which the process may occupy. 177 178 179.. data:: RLIMIT_AS 180 181 The maximum area (in bytes) of address space which may be taken by the process. 182 183 184.. data:: RLIMIT_MSGQUEUE 185 186 The number of bytes that can be allocated for POSIX message queues. 187 188 .. availability:: Linux 2.6.8 or later. 189 190 .. versionadded:: 3.4 191 192 193.. data:: RLIMIT_NICE 194 195 The ceiling for the process's nice level (calculated as 20 - rlim_cur). 196 197 .. availability:: Linux 2.6.12 or later. 198 199 .. versionadded:: 3.4 200 201 202.. data:: RLIMIT_RTPRIO 203 204 The ceiling of the real-time priority. 205 206 .. availability:: Linux 2.6.12 or later. 207 208 .. versionadded:: 3.4 209 210 211.. data:: RLIMIT_RTTIME 212 213 The time limit (in microseconds) on CPU time that a process can spend 214 under real-time scheduling without making a blocking syscall. 215 216 .. availability:: Linux 2.6.25 or later. 217 218 .. versionadded:: 3.4 219 220 221.. data:: RLIMIT_SIGPENDING 222 223 The number of signals which the process may queue. 224 225 .. availability:: Linux 2.6.8 or later. 226 227 .. versionadded:: 3.4 228 229.. data:: RLIMIT_SBSIZE 230 231 The maximum size (in bytes) of socket buffer usage for this user. 232 This limits the amount of network memory, and hence the amount of mbufs, 233 that this user may hold at any time. 234 235 .. availability:: FreeBSD 9 or later. 236 237 .. versionadded:: 3.4 238 239.. data:: RLIMIT_SWAP 240 241 The maximum size (in bytes) of the swap space that may be reserved or 242 used by all of this user id's processes. 243 This limit is enforced only if bit 1 of the vm.overcommit sysctl is set. 244 Please see 245 `tuning(7) <https://www.freebsd.org/cgi/man.cgi?query=tuning&sektion=7>`__ 246 for a complete description of this sysctl. 247 248 .. availability:: FreeBSD 9 or later. 249 250 .. versionadded:: 3.4 251 252.. data:: RLIMIT_NPTS 253 254 The maximum number of pseudo-terminals created by this user id. 255 256 .. availability:: FreeBSD 9 or later. 257 258 .. versionadded:: 3.4 259 260.. data:: RLIMIT_KQUEUES 261 262 The maximum number of kqueues this user id is allowed to create. 263 264 .. availability:: FreeBSD 11 or later. 265 266 .. versionadded:: 3.10 267 268Resource Usage 269-------------- 270 271These functions are used to retrieve resource usage information: 272 273 274.. function:: getrusage(who) 275 276 This function returns an object that describes the resources consumed by either 277 the current process or its children, as specified by the *who* parameter. The 278 *who* parameter should be specified using one of the :const:`RUSAGE_\*` 279 constants described below. 280 281 A simple example:: 282 283 from resource import * 284 import time 285 286 # a non CPU-bound task 287 time.sleep(3) 288 print(getrusage(RUSAGE_SELF)) 289 290 # a CPU-bound task 291 for i in range(10 ** 8): 292 _ = 1 + 1 293 print(getrusage(RUSAGE_SELF)) 294 295 The fields of the return value each describe how a particular system resource 296 has been used, e.g. amount of time spent running is user mode or number of times 297 the process was swapped out of main memory. Some values are dependent on the 298 clock tick internal, e.g. the amount of memory the process is using. 299 300 For backward compatibility, the return value is also accessible as a tuple of 16 301 elements. 302 303 The fields :attr:`ru_utime` and :attr:`ru_stime` of the return value are 304 floating point values representing the amount of time spent executing in user 305 mode and the amount of time spent executing in system mode, respectively. The 306 remaining values are integers. Consult the :manpage:`getrusage(2)` man page for 307 detailed information about these values. A brief summary is presented here: 308 309 +--------+---------------------+---------------------------------------+ 310 | Index | Field | Resource | 311 +========+=====================+=======================================+ 312 | ``0`` | :attr:`ru_utime` | time in user mode (float seconds) | 313 +--------+---------------------+---------------------------------------+ 314 | ``1`` | :attr:`ru_stime` | time in system mode (float seconds) | 315 +--------+---------------------+---------------------------------------+ 316 | ``2`` | :attr:`ru_maxrss` | maximum resident set size | 317 +--------+---------------------+---------------------------------------+ 318 | ``3`` | :attr:`ru_ixrss` | shared memory size | 319 +--------+---------------------+---------------------------------------+ 320 | ``4`` | :attr:`ru_idrss` | unshared memory size | 321 +--------+---------------------+---------------------------------------+ 322 | ``5`` | :attr:`ru_isrss` | unshared stack size | 323 +--------+---------------------+---------------------------------------+ 324 | ``6`` | :attr:`ru_minflt` | page faults not requiring I/O | 325 +--------+---------------------+---------------------------------------+ 326 | ``7`` | :attr:`ru_majflt` | page faults requiring I/O | 327 +--------+---------------------+---------------------------------------+ 328 | ``8`` | :attr:`ru_nswap` | number of swap outs | 329 +--------+---------------------+---------------------------------------+ 330 | ``9`` | :attr:`ru_inblock` | block input operations | 331 +--------+---------------------+---------------------------------------+ 332 | ``10`` | :attr:`ru_oublock` | block output operations | 333 +--------+---------------------+---------------------------------------+ 334 | ``11`` | :attr:`ru_msgsnd` | messages sent | 335 +--------+---------------------+---------------------------------------+ 336 | ``12`` | :attr:`ru_msgrcv` | messages received | 337 +--------+---------------------+---------------------------------------+ 338 | ``13`` | :attr:`ru_nsignals` | signals received | 339 +--------+---------------------+---------------------------------------+ 340 | ``14`` | :attr:`ru_nvcsw` | voluntary context switches | 341 +--------+---------------------+---------------------------------------+ 342 | ``15`` | :attr:`ru_nivcsw` | involuntary context switches | 343 +--------+---------------------+---------------------------------------+ 344 345 This function will raise a :exc:`ValueError` if an invalid *who* parameter is 346 specified. It may also raise :exc:`error` exception in unusual circumstances. 347 348 349.. function:: getpagesize() 350 351 Returns the number of bytes in a system page. (This need not be the same as the 352 hardware page size.) 353 354The following :const:`RUSAGE_\*` symbols are passed to the :func:`getrusage` 355function to specify which processes information should be provided for. 356 357 358.. data:: RUSAGE_SELF 359 360 Pass to :func:`getrusage` to request resources consumed by the calling 361 process, which is the sum of resources used by all threads in the process. 362 363 364.. data:: RUSAGE_CHILDREN 365 366 Pass to :func:`getrusage` to request resources consumed by child processes 367 of the calling process which have been terminated and waited for. 368 369 370.. data:: RUSAGE_BOTH 371 372 Pass to :func:`getrusage` to request resources consumed by both the current 373 process and child processes. May not be available on all systems. 374 375 376.. data:: RUSAGE_THREAD 377 378 Pass to :func:`getrusage` to request resources consumed by the current 379 thread. May not be available on all systems. 380 381 .. versionadded:: 3.2 382