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 16.. availability:: Unix, not WASI. 17 18Symbolic constants are used to specify particular system resources and to 19request usage information about either the current process or its children. 20 21An :exc:`OSError` is raised on syscall failure. 22 23 24.. exception:: error 25 26 A deprecated alias of :exc:`OSError`. 27 28 .. versionchanged:: 3.3 29 Following :pep:`3151`, this class was made an alias of :exc:`OSError`. 30 31 32Resource Limits 33--------------- 34 35Resources usage can be limited using the :func:`setrlimit` function described 36below. Each resource is controlled by a pair of limits: a soft limit and a hard 37limit. The soft limit is the current limit, and may be lowered or raised by a 38process over time. The soft limit can never exceed the hard limit. The hard 39limit can be lowered to any value greater than the soft limit, but not raised. 40(Only processes with the effective UID of the super-user can raise a hard 41limit.) 42 43The specific resources that can be limited are system dependent. They are 44described in the :manpage:`getrlimit(2)` man page. The resources listed below 45are supported when the underlying operating system supports them; resources 46which cannot be checked or controlled by the operating system are not defined in 47this module for those platforms. 48 49 50.. data:: RLIM_INFINITY 51 52 Constant used to represent the limit for an unlimited resource. 53 54 55.. function:: getrlimit(resource) 56 57 Returns a tuple ``(soft, hard)`` with the current soft and hard limits of 58 *resource*. Raises :exc:`ValueError` if an invalid resource is specified, or 59 :exc:`error` if the underlying system call fails unexpectedly. 60 61 62.. function:: setrlimit(resource, limits) 63 64 Sets new limits of consumption of *resource*. The *limits* argument must be a 65 tuple ``(soft, hard)`` of two integers describing the new limits. A value of 66 :data:`~resource.RLIM_INFINITY` can be used to request a limit that is 67 unlimited. 68 69 Raises :exc:`ValueError` if an invalid resource is specified, if the new soft 70 limit exceeds the hard limit, or if a process tries to raise its hard limit. 71 Specifying a limit of :data:`~resource.RLIM_INFINITY` when the hard or 72 system limit for that resource is not unlimited will result in a 73 :exc:`ValueError`. A process with the effective UID of super-user can 74 request any valid limit value, including unlimited, but :exc:`ValueError` 75 will still be raised if the requested limit exceeds the system imposed 76 limit. 77 78 ``setrlimit`` may also raise :exc:`error` if the underlying system call 79 fails. 80 81 VxWorks only supports setting :data:`RLIMIT_NOFILE`. 82 83 .. audit-event:: resource.setrlimit resource,limits resource.setrlimit 84 85 86.. function:: prlimit(pid, resource[, limits]) 87 88 Combines :func:`setrlimit` and :func:`getrlimit` in one function and 89 supports to get and set the resources limits of an arbitrary process. If 90 *pid* is 0, then the call applies to the current process. *resource* and 91 *limits* have the same meaning as in :func:`setrlimit`, except that 92 *limits* is optional. 93 94 When *limits* is not given the function returns the *resource* limit of the 95 process *pid*. When *limits* is given the *resource* limit of the process is 96 set and the former resource limit is returned. 97 98 Raises :exc:`ProcessLookupError` when *pid* can't be found and 99 :exc:`PermissionError` when the user doesn't have ``CAP_SYS_RESOURCE`` for 100 the process. 101 102 .. audit-event:: resource.prlimit pid,resource,limits resource.prlimit 103 104 .. availability:: Linux >= 2.6.36 with glibc >= 2.13. 105 106 .. versionadded:: 3.4 107 108 109These symbols define resources whose consumption can be controlled using the 110:func:`setrlimit` and :func:`getrlimit` functions described below. The values of 111these symbols are exactly the constants used by C programs. 112 113The Unix man page for :manpage:`getrlimit(2)` lists the available resources. 114Note that not all systems use the same symbol or same value to denote the same 115resource. This module does not attempt to mask platform differences --- symbols 116not defined for a platform will not be available from this module on that 117platform. 118 119 120.. data:: RLIMIT_CORE 121 122 The maximum size (in bytes) of a core file that the current process can create. 123 This may result in the creation of a partial core file if a larger core would be 124 required to contain the entire process image. 125 126 127.. data:: RLIMIT_CPU 128 129 The maximum amount of processor time (in seconds) that a process can use. If 130 this limit is exceeded, a :const:`SIGXCPU` signal is sent to the process. (See 131 the :mod:`signal` module documentation for information about how to catch this 132 signal and do something useful, e.g. flush open files to disk.) 133 134 135.. data:: RLIMIT_FSIZE 136 137 The maximum size of a file which the process may create. 138 139 140.. data:: RLIMIT_DATA 141 142 The maximum size (in bytes) of the process's heap. 143 144 145.. data:: RLIMIT_STACK 146 147 The maximum size (in bytes) of the call stack for the current process. This only 148 affects the stack of the main thread in a multi-threaded process. 149 150 151.. data:: RLIMIT_RSS 152 153 The maximum resident set size that should be made available to the process. 154 155 156.. data:: RLIMIT_NPROC 157 158 The maximum number of processes the current process may create. 159 160 161.. data:: RLIMIT_NOFILE 162 163 The maximum number of open file descriptors for the current process. 164 165 166.. data:: RLIMIT_OFILE 167 168 The BSD name for :const:`RLIMIT_NOFILE`. 169 170 171.. data:: RLIMIT_MEMLOCK 172 173 The maximum address space which may be locked in memory. 174 175 176.. data:: RLIMIT_VMEM 177 178 The largest area of mapped memory which the process may occupy. 179 180 .. availability:: FreeBSD >= 11. 181 182 183.. data:: RLIMIT_AS 184 185 The maximum area (in bytes) of address space which may be taken by the process. 186 187 188.. data:: RLIMIT_MSGQUEUE 189 190 The number of bytes that can be allocated for POSIX message queues. 191 192 .. availability:: Linux >= 2.6.8. 193 194 .. versionadded:: 3.4 195 196 197.. data:: RLIMIT_NICE 198 199 The ceiling for the process's nice level (calculated as 20 - rlim_cur). 200 201 .. availability:: Linux >= 2.6.12. 202 203 .. versionadded:: 3.4 204 205 206.. data:: RLIMIT_RTPRIO 207 208 The ceiling of the real-time priority. 209 210 .. availability:: Linux >= 2.6.12. 211 212 .. versionadded:: 3.4 213 214 215.. data:: RLIMIT_RTTIME 216 217 The time limit (in microseconds) on CPU time that a process can spend 218 under real-time scheduling without making a blocking syscall. 219 220 .. availability:: Linux >= 2.6.25. 221 222 .. versionadded:: 3.4 223 224 225.. data:: RLIMIT_SIGPENDING 226 227 The number of signals which the process may queue. 228 229 .. availability:: Linux >= 2.6.8. 230 231 .. versionadded:: 3.4 232 233.. data:: RLIMIT_SBSIZE 234 235 The maximum size (in bytes) of socket buffer usage for this user. 236 This limits the amount of network memory, and hence the amount of mbufs, 237 that this user may hold at any time. 238 239 .. availability:: FreeBSD. 240 241 .. versionadded:: 3.4 242 243.. data:: RLIMIT_SWAP 244 245 The maximum size (in bytes) of the swap space that may be reserved or 246 used by all of this user id's processes. 247 This limit is enforced only if bit 1 of the vm.overcommit sysctl is set. 248 Please see 249 `tuning(7) <https://man.freebsd.org/cgi/man.cgi?query=tuning&sektion=7>`__ 250 for a complete description of this sysctl. 251 252 .. availability:: FreeBSD. 253 254 .. versionadded:: 3.4 255 256.. data:: RLIMIT_NPTS 257 258 The maximum number of pseudo-terminals created by this user id. 259 260 .. availability:: FreeBSD. 261 262 .. versionadded:: 3.4 263 264.. data:: RLIMIT_KQUEUES 265 266 The maximum number of kqueues this user id is allowed to create. 267 268 .. availability:: FreeBSD >= 11. 269 270 .. versionadded:: 3.10 271 272Resource Usage 273-------------- 274 275These functions are used to retrieve resource usage information: 276 277 278.. function:: getrusage(who) 279 280 This function returns an object that describes the resources consumed by either 281 the current process or its children, as specified by the *who* parameter. The 282 *who* parameter should be specified using one of the :const:`!RUSAGE_\*` 283 constants described below. 284 285 A simple example:: 286 287 from resource import * 288 import time 289 290 # a non CPU-bound task 291 time.sleep(3) 292 print(getrusage(RUSAGE_SELF)) 293 294 # a CPU-bound task 295 for i in range(10 ** 8): 296 _ = 1 + 1 297 print(getrusage(RUSAGE_SELF)) 298 299 The fields of the return value each describe how a particular system resource 300 has been used, e.g. amount of time spent running is user mode or number of times 301 the process was swapped out of main memory. Some values are dependent on the 302 clock tick internal, e.g. the amount of memory the process is using. 303 304 For backward compatibility, the return value is also accessible as a tuple of 16 305 elements. 306 307 The fields :attr:`ru_utime` and :attr:`ru_stime` of the return value are 308 floating-point values representing the amount of time spent executing in user 309 mode and the amount of time spent executing in system mode, respectively. The 310 remaining values are integers. Consult the :manpage:`getrusage(2)` man page for 311 detailed information about these values. A brief summary is presented here: 312 313 +--------+---------------------+---------------------------------------+ 314 | Index | Field | Resource | 315 +========+=====================+=======================================+ 316 | ``0`` | :attr:`ru_utime` | time in user mode (float seconds) | 317 +--------+---------------------+---------------------------------------+ 318 | ``1`` | :attr:`ru_stime` | time in system mode (float seconds) | 319 +--------+---------------------+---------------------------------------+ 320 | ``2`` | :attr:`ru_maxrss` | maximum resident set size | 321 +--------+---------------------+---------------------------------------+ 322 | ``3`` | :attr:`ru_ixrss` | shared memory size | 323 +--------+---------------------+---------------------------------------+ 324 | ``4`` | :attr:`ru_idrss` | unshared memory size | 325 +--------+---------------------+---------------------------------------+ 326 | ``5`` | :attr:`ru_isrss` | unshared stack size | 327 +--------+---------------------+---------------------------------------+ 328 | ``6`` | :attr:`ru_minflt` | page faults not requiring I/O | 329 +--------+---------------------+---------------------------------------+ 330 | ``7`` | :attr:`ru_majflt` | page faults requiring I/O | 331 +--------+---------------------+---------------------------------------+ 332 | ``8`` | :attr:`ru_nswap` | number of swap outs | 333 +--------+---------------------+---------------------------------------+ 334 | ``9`` | :attr:`ru_inblock` | block input operations | 335 +--------+---------------------+---------------------------------------+ 336 | ``10`` | :attr:`ru_oublock` | block output operations | 337 +--------+---------------------+---------------------------------------+ 338 | ``11`` | :attr:`ru_msgsnd` | messages sent | 339 +--------+---------------------+---------------------------------------+ 340 | ``12`` | :attr:`ru_msgrcv` | messages received | 341 +--------+---------------------+---------------------------------------+ 342 | ``13`` | :attr:`ru_nsignals` | signals received | 343 +--------+---------------------+---------------------------------------+ 344 | ``14`` | :attr:`ru_nvcsw` | voluntary context switches | 345 +--------+---------------------+---------------------------------------+ 346 | ``15`` | :attr:`ru_nivcsw` | involuntary context switches | 347 +--------+---------------------+---------------------------------------+ 348 349 This function will raise a :exc:`ValueError` if an invalid *who* parameter is 350 specified. It may also raise :exc:`error` exception in unusual circumstances. 351 352 353.. function:: getpagesize() 354 355 Returns the number of bytes in a system page. (This need not be the same as the 356 hardware page size.) 357 358The following :const:`!RUSAGE_\*` symbols are passed to the :func:`getrusage` 359function to specify which processes information should be provided for. 360 361 362.. data:: RUSAGE_SELF 363 364 Pass to :func:`getrusage` to request resources consumed by the calling 365 process, which is the sum of resources used by all threads in the process. 366 367 368.. data:: RUSAGE_CHILDREN 369 370 Pass to :func:`getrusage` to request resources consumed by child processes 371 of the calling process which have been terminated and waited for. 372 373 374.. data:: RUSAGE_BOTH 375 376 Pass to :func:`getrusage` to request resources consumed by both the current 377 process and child processes. May not be available on all systems. 378 379 380.. data:: RUSAGE_THREAD 381 382 Pass to :func:`getrusage` to request resources consumed by the current 383 thread. May not be available on all systems. 384 385 .. versionadded:: 3.2 386