| # |
| # Module which supports allocation of memory from an mmap |
| # |
| # multiprocessing/heap.py |
| # |
| # Copyright (c) 2006-2008, R Oudkerk |
| # Licensed to PSF under a Contributor Agreement. |
| # |
| |
| import bisect |
| import mmap |
| import os |
| import sys |
| import tempfile |
| import threading |
| |
| from .context import reduction, assert_spawning |
| from . import util |
| |
| __all__ = ['BufferWrapper'] |
| |
| # |
| # Inheritable class which wraps an mmap, and from which blocks can be allocated |
| # |
| |
| if sys.platform == 'win32': |
| |
| import _winapi |
| |
| class Arena(object): |
| |
| _rand = tempfile._RandomNameSequence() |
| |
| def __init__(self, size): |
| self.size = size |
| for i in range(100): |
| name = 'pym-%d-%s' % (os.getpid(), next(self._rand)) |
| buf = mmap.mmap(-1, size, tagname=name) |
| if _winapi.GetLastError() == 0: |
| break |
| # We have reopened a preexisting mmap. |
| buf.close() |
| else: |
| raise FileExistsError('Cannot find name for new mmap') |
| self.name = name |
| self.buffer = buf |
| 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) |
| # XXX Temporarily preventing buildbot failures while determining |
| # XXX the correct long-term fix. See issue 23060 |
| #assert _winapi.GetLastError() == _winapi.ERROR_ALREADY_EXISTS |
| |
| else: |
| |
| class Arena(object): |
| |
| def __init__(self, size, fd=-1): |
| self.size = size |
| self.fd = fd |
| if fd == -1: |
| self.fd, name = tempfile.mkstemp( |
| prefix='pym-%d-'%os.getpid(), dir=util.get_temp_dir()) |
| os.unlink(name) |
| util.Finalize(self, os.close, (self.fd,)) |
| with open(self.fd, 'wb', closefd=False) as f: |
| bs = 1024 * 1024 |
| if size >= bs: |
| zeros = b'\0' * bs |
| for _ in range(size // bs): |
| f.write(zeros) |
| del zeros |
| f.write(b'\0' * (size % bs)) |
| assert f.tell() == size |
| self.buffer = mmap.mmap(self.fd, self.size) |
| |
| def reduce_arena(a): |
| if a.fd == -1: |
| raise ValueError('Arena is unpicklable because ' |
| 'forking was enabled when it was created') |
| return rebuild_arena, (a.size, reduction.DupFd(a.fd)) |
| |
| def rebuild_arena(size, dupfd): |
| return Arena(size, dupfd.detach()) |
| |
| reduction.register(Arena, reduce_arena) |
| |
| # |
| # 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 |
| util.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 |
| with self._lock: |
| self._free_pending_blocks() |
| 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 |
| |
| # |
| # Class representing a chunk of an mmap -- can be inherited by child process |
| # |
| |
| class BufferWrapper(object): |
| |
| _heap = Heap() |
| |
| def __init__(self, size): |
| assert 0 <= size < sys.maxsize |
| block = BufferWrapper._heap.malloc(size) |
| self._state = (block, size) |
| util.Finalize(self, BufferWrapper._heap.free, args=(block,)) |
| |
| def create_memoryview(self): |
| (arena, start, stop), size = self._state |
| return memoryview(arena.buffer)[start:start+size] |