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annotate CSP2/CSP2_env/env-d9b9114564458d9d-741b3de822f2aaca6c6caa4325c4afce/lib/python3.8/multiprocessing/heap.py @ 69:33d812a61356

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planemo upload commit 2e9511a184a1ca667c7be0c6321a36dc4e3d116d
author jpayne
date Tue, 18 Mar 2025 17:55:14 -0400
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jpayne@69 1 #
jpayne@69 2 # Module which supports allocation of memory from an mmap
jpayne@69 3 #
jpayne@69 4 # multiprocessing/heap.py
jpayne@69 5 #
jpayne@69 6 # Copyright (c) 2006-2008, R Oudkerk
jpayne@69 7 # Licensed to PSF under a Contributor Agreement.
jpayne@69 8 #
jpayne@69 9
jpayne@69 10 import bisect
jpayne@69 11 from collections import defaultdict
jpayne@69 12 import mmap
jpayne@69 13 import os
jpayne@69 14 import sys
jpayne@69 15 import tempfile
jpayne@69 16 import threading
jpayne@69 17
jpayne@69 18 from .context import reduction, assert_spawning
jpayne@69 19 from . import util
jpayne@69 20
jpayne@69 21 __all__ = ['BufferWrapper']
jpayne@69 22
jpayne@69 23 #
jpayne@69 24 # Inheritable class which wraps an mmap, and from which blocks can be allocated
jpayne@69 25 #
jpayne@69 26
jpayne@69 27 if sys.platform == 'win32':
jpayne@69 28
jpayne@69 29 import _winapi
jpayne@69 30
jpayne@69 31 class Arena(object):
jpayne@69 32 """
jpayne@69 33 A shared memory area backed by anonymous memory (Windows).
jpayne@69 34 """
jpayne@69 35
jpayne@69 36 _rand = tempfile._RandomNameSequence()
jpayne@69 37
jpayne@69 38 def __init__(self, size):
jpayne@69 39 self.size = size
jpayne@69 40 for i in range(100):
jpayne@69 41 name = 'pym-%d-%s' % (os.getpid(), next(self._rand))
jpayne@69 42 buf = mmap.mmap(-1, size, tagname=name)
jpayne@69 43 if _winapi.GetLastError() == 0:
jpayne@69 44 break
jpayne@69 45 # We have reopened a preexisting mmap.
jpayne@69 46 buf.close()
jpayne@69 47 else:
jpayne@69 48 raise FileExistsError('Cannot find name for new mmap')
jpayne@69 49 self.name = name
jpayne@69 50 self.buffer = buf
jpayne@69 51 self._state = (self.size, self.name)
jpayne@69 52
jpayne@69 53 def __getstate__(self):
jpayne@69 54 assert_spawning(self)
jpayne@69 55 return self._state
jpayne@69 56
jpayne@69 57 def __setstate__(self, state):
jpayne@69 58 self.size, self.name = self._state = state
jpayne@69 59 # Reopen existing mmap
jpayne@69 60 self.buffer = mmap.mmap(-1, self.size, tagname=self.name)
jpayne@69 61 # XXX Temporarily preventing buildbot failures while determining
jpayne@69 62 # XXX the correct long-term fix. See issue 23060
jpayne@69 63 #assert _winapi.GetLastError() == _winapi.ERROR_ALREADY_EXISTS
jpayne@69 64
jpayne@69 65 else:
jpayne@69 66
jpayne@69 67 class Arena(object):
jpayne@69 68 """
jpayne@69 69 A shared memory area backed by a temporary file (POSIX).
jpayne@69 70 """
jpayne@69 71
jpayne@69 72 if sys.platform == 'linux':
jpayne@69 73 _dir_candidates = ['/dev/shm']
jpayne@69 74 else:
jpayne@69 75 _dir_candidates = []
jpayne@69 76
jpayne@69 77 def __init__(self, size, fd=-1):
jpayne@69 78 self.size = size
jpayne@69 79 self.fd = fd
jpayne@69 80 if fd == -1:
jpayne@69 81 # Arena is created anew (if fd != -1, it means we're coming
jpayne@69 82 # from rebuild_arena() below)
jpayne@69 83 self.fd, name = tempfile.mkstemp(
jpayne@69 84 prefix='pym-%d-'%os.getpid(),
jpayne@69 85 dir=self._choose_dir(size))
jpayne@69 86 os.unlink(name)
jpayne@69 87 util.Finalize(self, os.close, (self.fd,))
jpayne@69 88 os.ftruncate(self.fd, size)
jpayne@69 89 self.buffer = mmap.mmap(self.fd, self.size)
jpayne@69 90
jpayne@69 91 def _choose_dir(self, size):
jpayne@69 92 # Choose a non-storage backed directory if possible,
jpayne@69 93 # to improve performance
jpayne@69 94 for d in self._dir_candidates:
jpayne@69 95 st = os.statvfs(d)
jpayne@69 96 if st.f_bavail * st.f_frsize >= size: # enough free space?
jpayne@69 97 return d
jpayne@69 98 return util.get_temp_dir()
jpayne@69 99
jpayne@69 100 def reduce_arena(a):
jpayne@69 101 if a.fd == -1:
jpayne@69 102 raise ValueError('Arena is unpicklable because '
jpayne@69 103 'forking was enabled when it was created')
jpayne@69 104 return rebuild_arena, (a.size, reduction.DupFd(a.fd))
jpayne@69 105
jpayne@69 106 def rebuild_arena(size, dupfd):
jpayne@69 107 return Arena(size, dupfd.detach())
jpayne@69 108
jpayne@69 109 reduction.register(Arena, reduce_arena)
jpayne@69 110
jpayne@69 111 #
jpayne@69 112 # Class allowing allocation of chunks of memory from arenas
jpayne@69 113 #
jpayne@69 114
jpayne@69 115 class Heap(object):
jpayne@69 116
jpayne@69 117 # Minimum malloc() alignment
jpayne@69 118 _alignment = 8
jpayne@69 119
jpayne@69 120 _DISCARD_FREE_SPACE_LARGER_THAN = 4 * 1024 ** 2 # 4 MB
jpayne@69 121 _DOUBLE_ARENA_SIZE_UNTIL = 4 * 1024 ** 2
jpayne@69 122
jpayne@69 123 def __init__(self, size=mmap.PAGESIZE):
jpayne@69 124 self._lastpid = os.getpid()
jpayne@69 125 self._lock = threading.Lock()
jpayne@69 126 # Current arena allocation size
jpayne@69 127 self._size = size
jpayne@69 128 # A sorted list of available block sizes in arenas
jpayne@69 129 self._lengths = []
jpayne@69 130
jpayne@69 131 # Free block management:
jpayne@69 132 # - map each block size to a list of `(Arena, start, stop)` blocks
jpayne@69 133 self._len_to_seq = {}
jpayne@69 134 # - map `(Arena, start)` tuple to the `(Arena, start, stop)` block
jpayne@69 135 # starting at that offset
jpayne@69 136 self._start_to_block = {}
jpayne@69 137 # - map `(Arena, stop)` tuple to the `(Arena, start, stop)` block
jpayne@69 138 # ending at that offset
jpayne@69 139 self._stop_to_block = {}
jpayne@69 140
jpayne@69 141 # Map arenas to their `(Arena, start, stop)` blocks in use
jpayne@69 142 self._allocated_blocks = defaultdict(set)
jpayne@69 143 self._arenas = []
jpayne@69 144
jpayne@69 145 # List of pending blocks to free - see comment in free() below
jpayne@69 146 self._pending_free_blocks = []
jpayne@69 147
jpayne@69 148 # Statistics
jpayne@69 149 self._n_mallocs = 0
jpayne@69 150 self._n_frees = 0
jpayne@69 151
jpayne@69 152 @staticmethod
jpayne@69 153 def _roundup(n, alignment):
jpayne@69 154 # alignment must be a power of 2
jpayne@69 155 mask = alignment - 1
jpayne@69 156 return (n + mask) & ~mask
jpayne@69 157
jpayne@69 158 def _new_arena(self, size):
jpayne@69 159 # Create a new arena with at least the given *size*
jpayne@69 160 length = self._roundup(max(self._size, size), mmap.PAGESIZE)
jpayne@69 161 # We carve larger and larger arenas, for efficiency, until we
jpayne@69 162 # reach a large-ish size (roughly L3 cache-sized)
jpayne@69 163 if self._size < self._DOUBLE_ARENA_SIZE_UNTIL:
jpayne@69 164 self._size *= 2
jpayne@69 165 util.info('allocating a new mmap of length %d', length)
jpayne@69 166 arena = Arena(length)
jpayne@69 167 self._arenas.append(arena)
jpayne@69 168 return (arena, 0, length)
jpayne@69 169
jpayne@69 170 def _discard_arena(self, arena):
jpayne@69 171 # Possibly delete the given (unused) arena
jpayne@69 172 length = arena.size
jpayne@69 173 # Reusing an existing arena is faster than creating a new one, so
jpayne@69 174 # we only reclaim space if it's large enough.
jpayne@69 175 if length < self._DISCARD_FREE_SPACE_LARGER_THAN:
jpayne@69 176 return
jpayne@69 177 blocks = self._allocated_blocks.pop(arena)
jpayne@69 178 assert not blocks
jpayne@69 179 del self._start_to_block[(arena, 0)]
jpayne@69 180 del self._stop_to_block[(arena, length)]
jpayne@69 181 self._arenas.remove(arena)
jpayne@69 182 seq = self._len_to_seq[length]
jpayne@69 183 seq.remove((arena, 0, length))
jpayne@69 184 if not seq:
jpayne@69 185 del self._len_to_seq[length]
jpayne@69 186 self._lengths.remove(length)
jpayne@69 187
jpayne@69 188 def _malloc(self, size):
jpayne@69 189 # returns a large enough block -- it might be much larger
jpayne@69 190 i = bisect.bisect_left(self._lengths, size)
jpayne@69 191 if i == len(self._lengths):
jpayne@69 192 return self._new_arena(size)
jpayne@69 193 else:
jpayne@69 194 length = self._lengths[i]
jpayne@69 195 seq = self._len_to_seq[length]
jpayne@69 196 block = seq.pop()
jpayne@69 197 if not seq:
jpayne@69 198 del self._len_to_seq[length], self._lengths[i]
jpayne@69 199
jpayne@69 200 (arena, start, stop) = block
jpayne@69 201 del self._start_to_block[(arena, start)]
jpayne@69 202 del self._stop_to_block[(arena, stop)]
jpayne@69 203 return block
jpayne@69 204
jpayne@69 205 def _add_free_block(self, block):
jpayne@69 206 # make block available and try to merge with its neighbours in the arena
jpayne@69 207 (arena, start, stop) = block
jpayne@69 208
jpayne@69 209 try:
jpayne@69 210 prev_block = self._stop_to_block[(arena, start)]
jpayne@69 211 except KeyError:
jpayne@69 212 pass
jpayne@69 213 else:
jpayne@69 214 start, _ = self._absorb(prev_block)
jpayne@69 215
jpayne@69 216 try:
jpayne@69 217 next_block = self._start_to_block[(arena, stop)]
jpayne@69 218 except KeyError:
jpayne@69 219 pass
jpayne@69 220 else:
jpayne@69 221 _, stop = self._absorb(next_block)
jpayne@69 222
jpayne@69 223 block = (arena, start, stop)
jpayne@69 224 length = stop - start
jpayne@69 225
jpayne@69 226 try:
jpayne@69 227 self._len_to_seq[length].append(block)
jpayne@69 228 except KeyError:
jpayne@69 229 self._len_to_seq[length] = [block]
jpayne@69 230 bisect.insort(self._lengths, length)
jpayne@69 231
jpayne@69 232 self._start_to_block[(arena, start)] = block
jpayne@69 233 self._stop_to_block[(arena, stop)] = block
jpayne@69 234
jpayne@69 235 def _absorb(self, block):
jpayne@69 236 # deregister this block so it can be merged with a neighbour
jpayne@69 237 (arena, start, stop) = block
jpayne@69 238 del self._start_to_block[(arena, start)]
jpayne@69 239 del self._stop_to_block[(arena, stop)]
jpayne@69 240
jpayne@69 241 length = stop - start
jpayne@69 242 seq = self._len_to_seq[length]
jpayne@69 243 seq.remove(block)
jpayne@69 244 if not seq:
jpayne@69 245 del self._len_to_seq[length]
jpayne@69 246 self._lengths.remove(length)
jpayne@69 247
jpayne@69 248 return start, stop
jpayne@69 249
jpayne@69 250 def _remove_allocated_block(self, block):
jpayne@69 251 arena, start, stop = block
jpayne@69 252 blocks = self._allocated_blocks[arena]
jpayne@69 253 blocks.remove((start, stop))
jpayne@69 254 if not blocks:
jpayne@69 255 # Arena is entirely free, discard it from this process
jpayne@69 256 self._discard_arena(arena)
jpayne@69 257
jpayne@69 258 def _free_pending_blocks(self):
jpayne@69 259 # Free all the blocks in the pending list - called with the lock held.
jpayne@69 260 while True:
jpayne@69 261 try:
jpayne@69 262 block = self._pending_free_blocks.pop()
jpayne@69 263 except IndexError:
jpayne@69 264 break
jpayne@69 265 self._add_free_block(block)
jpayne@69 266 self._remove_allocated_block(block)
jpayne@69 267
jpayne@69 268 def free(self, block):
jpayne@69 269 # free a block returned by malloc()
jpayne@69 270 # Since free() can be called asynchronously by the GC, it could happen
jpayne@69 271 # that it's called while self._lock is held: in that case,
jpayne@69 272 # self._lock.acquire() would deadlock (issue #12352). To avoid that, a
jpayne@69 273 # trylock is used instead, and if the lock can't be acquired
jpayne@69 274 # immediately, the block is added to a list of blocks to be freed
jpayne@69 275 # synchronously sometimes later from malloc() or free(), by calling
jpayne@69 276 # _free_pending_blocks() (appending and retrieving from a list is not
jpayne@69 277 # strictly thread-safe but under CPython it's atomic thanks to the GIL).
jpayne@69 278 if os.getpid() != self._lastpid:
jpayne@69 279 raise ValueError(
jpayne@69 280 "My pid ({0:n}) is not last pid {1:n}".format(
jpayne@69 281 os.getpid(),self._lastpid))
jpayne@69 282 if not self._lock.acquire(False):
jpayne@69 283 # can't acquire the lock right now, add the block to the list of
jpayne@69 284 # pending blocks to free
jpayne@69 285 self._pending_free_blocks.append(block)
jpayne@69 286 else:
jpayne@69 287 # we hold the lock
jpayne@69 288 try:
jpayne@69 289 self._n_frees += 1
jpayne@69 290 self._free_pending_blocks()
jpayne@69 291 self._add_free_block(block)
jpayne@69 292 self._remove_allocated_block(block)
jpayne@69 293 finally:
jpayne@69 294 self._lock.release()
jpayne@69 295
jpayne@69 296 def malloc(self, size):
jpayne@69 297 # return a block of right size (possibly rounded up)
jpayne@69 298 if size < 0:
jpayne@69 299 raise ValueError("Size {0:n} out of range".format(size))
jpayne@69 300 if sys.maxsize <= size:
jpayne@69 301 raise OverflowError("Size {0:n} too large".format(size))
jpayne@69 302 if os.getpid() != self._lastpid:
jpayne@69 303 self.__init__() # reinitialize after fork
jpayne@69 304 with self._lock:
jpayne@69 305 self._n_mallocs += 1
jpayne@69 306 # allow pending blocks to be marked available
jpayne@69 307 self._free_pending_blocks()
jpayne@69 308 size = self._roundup(max(size, 1), self._alignment)
jpayne@69 309 (arena, start, stop) = self._malloc(size)
jpayne@69 310 real_stop = start + size
jpayne@69 311 if real_stop < stop:
jpayne@69 312 # if the returned block is larger than necessary, mark
jpayne@69 313 # the remainder available
jpayne@69 314 self._add_free_block((arena, real_stop, stop))
jpayne@69 315 self._allocated_blocks[arena].add((start, real_stop))
jpayne@69 316 return (arena, start, real_stop)
jpayne@69 317
jpayne@69 318 #
jpayne@69 319 # Class wrapping a block allocated out of a Heap -- can be inherited by child process
jpayne@69 320 #
jpayne@69 321
jpayne@69 322 class BufferWrapper(object):
jpayne@69 323
jpayne@69 324 _heap = Heap()
jpayne@69 325
jpayne@69 326 def __init__(self, size):
jpayne@69 327 if size < 0:
jpayne@69 328 raise ValueError("Size {0:n} out of range".format(size))
jpayne@69 329 if sys.maxsize <= size:
jpayne@69 330 raise OverflowError("Size {0:n} too large".format(size))
jpayne@69 331 block = BufferWrapper._heap.malloc(size)
jpayne@69 332 self._state = (block, size)
jpayne@69 333 util.Finalize(self, BufferWrapper._heap.free, args=(block,))
jpayne@69 334
jpayne@69 335 def create_memoryview(self):
jpayne@69 336 (arena, start, stop), size = self._state
jpayne@69 337 return memoryview(arena.buffer)[start:start+size]