| # |
| # Module which supports allocation of memory from an mmap |
| # |
| # multiprocessing/heap.py |
| # |
| # Copyright (c) 2006-2008, R Oudkerk |
| # All rights reserved. |
| # |
| # Redistribution and use in source and binary forms, with or without |
| # modification, are permitted provided that the following conditions |
| # are met: |
| # |
| # 1. Redistributions of source code must retain the above copyright |
| # notice, this list of conditions and the following disclaimer. |
| # 2. Redistributions in binary form must reproduce the above copyright |
| # notice, this list of conditions and the following disclaimer in the |
| # documentation and/or other materials provided with the distribution. |
| # 3. Neither the name of author nor the names of any contributors may be |
| # used to endorse or promote products derived from this software |
| # without specific prior written permission. |
| # |
| # THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND |
| # ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| # IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| # ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE |
| # FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
| # DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
| # OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| # HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
| # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
| # OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
| # SUCH DAMAGE. |
| # |
| |
| import bisect |
| import mmap |
| import tempfile |
| import os |
| import sys |
| import threading |
| import itertools |
| |
| import _multiprocessing |
| from multiprocessing.util import Finalize, info |
| from multiprocessing.forking import assert_spawning |
| |
| __all__ = ['BufferWrapper'] |
| |
| # |
| # Inheirtable class which wraps an mmap, and from which blocks can be allocated |
| # |
| |
| if sys.platform == 'win32': |
| |
| from _multiprocessing import win32 |
| |
| class Arena(object): |
| |
| _counter = itertools.count() |
| |
| def __init__(self, size): |
| self.size = size |
| self.name = 'pym-%d-%d' % (os.getpid(), next(Arena._counter)) |
| self.buffer = mmap.mmap(-1, self.size, tagname=self.name) |
| assert win32.GetLastError() == 0, 'tagname already in use' |
| self._state = (self.size, self.name) |
| |
| def __getstate__(self): |
| assert_spawning(self) |
| return self._state |
| |
| def __setstate__(self, state): |
| self.size, self.name = self._state = state |
| self.buffer = mmap.mmap(-1, self.size, tagname=self.name) |
| assert win32.GetLastError() == win32.ERROR_ALREADY_EXISTS |
| |
| else: |
| |
| class Arena(object): |
| |
| def __init__(self, size): |
| self.buffer = mmap.mmap(-1, size) |
| self.size = size |
| self.name = None |
| |
| # |
| # Class allowing allocation of chunks of memory from arenas |
| # |
| |
| class Heap(object): |
| |
| _alignment = 8 |
| |
| def __init__(self, size=mmap.PAGESIZE): |
| self._lastpid = os.getpid() |
| self._lock = threading.Lock() |
| self._size = size |
| self._lengths = [] |
| self._len_to_seq = {} |
| self._start_to_block = {} |
| self._stop_to_block = {} |
| self._allocated_blocks = set() |
| self._arenas = [] |
| # list of pending blocks to free - see free() comment below |
| self._pending_free_blocks = [] |
| |
| @staticmethod |
| def _roundup(n, alignment): |
| # alignment must be a power of 2 |
| mask = alignment - 1 |
| return (n + mask) & ~mask |
| |
| def _malloc(self, size): |
| # returns a large enough block -- it might be much larger |
| i = bisect.bisect_left(self._lengths, size) |
| if i == len(self._lengths): |
| length = self._roundup(max(self._size, size), mmap.PAGESIZE) |
| self._size *= 2 |
| info('allocating a new mmap of length %d', length) |
| arena = Arena(length) |
| self._arenas.append(arena) |
| return (arena, 0, length) |
| else: |
| length = self._lengths[i] |
| seq = self._len_to_seq[length] |
| block = seq.pop() |
| if not seq: |
| del self._len_to_seq[length], self._lengths[i] |
| |
| (arena, start, stop) = block |
| del self._start_to_block[(arena, start)] |
| del self._stop_to_block[(arena, stop)] |
| return block |
| |
| def _free(self, block): |
| # free location and try to merge with neighbours |
| (arena, start, stop) = block |
| |
| try: |
| prev_block = self._stop_to_block[(arena, start)] |
| except KeyError: |
| pass |
| else: |
| start, _ = self._absorb(prev_block) |
| |
| try: |
| next_block = self._start_to_block[(arena, stop)] |
| except KeyError: |
| pass |
| else: |
| _, stop = self._absorb(next_block) |
| |
| block = (arena, start, stop) |
| length = stop - start |
| |
| try: |
| self._len_to_seq[length].append(block) |
| except KeyError: |
| self._len_to_seq[length] = [block] |
| bisect.insort(self._lengths, length) |
| |
| self._start_to_block[(arena, start)] = block |
| self._stop_to_block[(arena, stop)] = block |
| |
| def _absorb(self, block): |
| # deregister this block so it can be merged with a neighbour |
| (arena, start, stop) = block |
| del self._start_to_block[(arena, start)] |
| del self._stop_to_block[(arena, stop)] |
| |
| length = stop - start |
| seq = self._len_to_seq[length] |
| seq.remove(block) |
| if not seq: |
| del self._len_to_seq[length] |
| self._lengths.remove(length) |
| |
| return start, stop |
| |
| def _free_pending_blocks(self): |
| # Free all the blocks in the pending list - called with the lock held. |
| while True: |
| try: |
| block = self._pending_free_blocks.pop() |
| except IndexError: |
| break |
| self._allocated_blocks.remove(block) |
| self._free(block) |
| |
| def free(self, block): |
| # free a block returned by malloc() |
| # Since free() can be called asynchronously by the GC, it could happen |
| # that it's called while self._lock is held: in that case, |
| # self._lock.acquire() would deadlock (issue #12352). To avoid that, a |
| # trylock is used instead, and if the lock can't be acquired |
| # immediately, the block is added to a list of blocks to be freed |
| # synchronously sometimes later from malloc() or free(), by calling |
| # _free_pending_blocks() (appending and retrieving from a list is not |
| # strictly thread-safe but under cPython it's atomic thanks to the GIL). |
| assert os.getpid() == self._lastpid |
| if not self._lock.acquire(False): |
| # can't acquire the lock right now, add the block to the list of |
| # pending blocks to free |
| self._pending_free_blocks.append(block) |
| else: |
| # we hold the lock |
| try: |
| self._free_pending_blocks() |
| self._allocated_blocks.remove(block) |
| self._free(block) |
| finally: |
| self._lock.release() |
| |
| def malloc(self, size): |
| # return a block of right size (possibly rounded up) |
| assert 0 <= size < sys.maxsize |
| if os.getpid() != self._lastpid: |
| self.__init__() # reinitialize after fork |
| self._lock.acquire() |
| self._free_pending_blocks() |
| try: |
| size = self._roundup(max(size,1), self._alignment) |
| (arena, start, stop) = self._malloc(size) |
| new_stop = start + size |
| if new_stop < stop: |
| self._free((arena, new_stop, stop)) |
| block = (arena, start, new_stop) |
| self._allocated_blocks.add(block) |
| return block |
| finally: |
| self._lock.release() |
| |
| # |
| # Class representing a chunk of an mmap -- can be inherited |
| # |
| |
| class BufferWrapper(object): |
| |
| _heap = Heap() |
| |
| def __init__(self, size): |
| assert 0 <= size < sys.maxsize |
| block = BufferWrapper._heap.malloc(size) |
| self._state = (block, size) |
| Finalize(self, BufferWrapper._heap.free, args=(block,)) |
| |
| def get_address(self): |
| (arena, start, stop), size = self._state |
| address, length = _multiprocessing.address_of_buffer(arena.buffer) |
| assert size <= length |
| return address + start |
| |
| def get_size(self): |
| return self._state[1] |