jpayne@69: #
jpayne@69: # Module which supports allocation of memory from an mmap
jpayne@69: #
jpayne@69: # multiprocessing/heap.py
jpayne@69: #
jpayne@69: # Copyright (c) 2006-2008, R Oudkerk
jpayne@69: # Licensed to PSF under a Contributor Agreement.
jpayne@69: #
jpayne@69: 
jpayne@69: import bisect
jpayne@69: from collections import defaultdict
jpayne@69: import mmap
jpayne@69: import os
jpayne@69: import sys
jpayne@69: import tempfile
jpayne@69: import threading
jpayne@69: 
jpayne@69: from .context import reduction, assert_spawning
jpayne@69: from . import util
jpayne@69: 
jpayne@69: __all__ = ['BufferWrapper']
jpayne@69: 
jpayne@69: #
jpayne@69: # Inheritable class which wraps an mmap, and from which blocks can be allocated
jpayne@69: #
jpayne@69: 
jpayne@69: if sys.platform == 'win32':
jpayne@69: 
jpayne@69:     import _winapi
jpayne@69: 
jpayne@69:     class Arena(object):
jpayne@69:         """
jpayne@69:         A shared memory area backed by anonymous memory (Windows).
jpayne@69:         """
jpayne@69: 
jpayne@69:         _rand = tempfile._RandomNameSequence()
jpayne@69: 
jpayne@69:         def __init__(self, size):
jpayne@69:             self.size = size
jpayne@69:             for i in range(100):
jpayne@69:                 name = 'pym-%d-%s' % (os.getpid(), next(self._rand))
jpayne@69:                 buf = mmap.mmap(-1, size, tagname=name)
jpayne@69:                 if _winapi.GetLastError() == 0:
jpayne@69:                     break
jpayne@69:                 # We have reopened a preexisting mmap.
jpayne@69:                 buf.close()
jpayne@69:             else:
jpayne@69:                 raise FileExistsError('Cannot find name for new mmap')
jpayne@69:             self.name = name
jpayne@69:             self.buffer = buf
jpayne@69:             self._state = (self.size, self.name)
jpayne@69: 
jpayne@69:         def __getstate__(self):
jpayne@69:             assert_spawning(self)
jpayne@69:             return self._state
jpayne@69: 
jpayne@69:         def __setstate__(self, state):
jpayne@69:             self.size, self.name = self._state = state
jpayne@69:             # Reopen existing mmap
jpayne@69:             self.buffer = mmap.mmap(-1, self.size, tagname=self.name)
jpayne@69:             # XXX Temporarily preventing buildbot failures while determining
jpayne@69:             # XXX the correct long-term fix. See issue 23060
jpayne@69:             #assert _winapi.GetLastError() == _winapi.ERROR_ALREADY_EXISTS
jpayne@69: 
jpayne@69: else:
jpayne@69: 
jpayne@69:     class Arena(object):
jpayne@69:         """
jpayne@69:         A shared memory area backed by a temporary file (POSIX).
jpayne@69:         """
jpayne@69: 
jpayne@69:         if sys.platform == 'linux':
jpayne@69:             _dir_candidates = ['/dev/shm']
jpayne@69:         else:
jpayne@69:             _dir_candidates = []
jpayne@69: 
jpayne@69:         def __init__(self, size, fd=-1):
jpayne@69:             self.size = size
jpayne@69:             self.fd = fd
jpayne@69:             if fd == -1:
jpayne@69:                 # Arena is created anew (if fd != -1, it means we're coming
jpayne@69:                 # from rebuild_arena() below)
jpayne@69:                 self.fd, name = tempfile.mkstemp(
jpayne@69:                      prefix='pym-%d-'%os.getpid(),
jpayne@69:                      dir=self._choose_dir(size))
jpayne@69:                 os.unlink(name)
jpayne@69:                 util.Finalize(self, os.close, (self.fd,))
jpayne@69:                 os.ftruncate(self.fd, size)
jpayne@69:             self.buffer = mmap.mmap(self.fd, self.size)
jpayne@69: 
jpayne@69:         def _choose_dir(self, size):
jpayne@69:             # Choose a non-storage backed directory if possible,
jpayne@69:             # to improve performance
jpayne@69:             for d in self._dir_candidates:
jpayne@69:                 st = os.statvfs(d)
jpayne@69:                 if st.f_bavail * st.f_frsize >= size:  # enough free space?
jpayne@69:                     return d
jpayne@69:             return util.get_temp_dir()
jpayne@69: 
jpayne@69:     def reduce_arena(a):
jpayne@69:         if a.fd == -1:
jpayne@69:             raise ValueError('Arena is unpicklable because '
jpayne@69:                              'forking was enabled when it was created')
jpayne@69:         return rebuild_arena, (a.size, reduction.DupFd(a.fd))
jpayne@69: 
jpayne@69:     def rebuild_arena(size, dupfd):
jpayne@69:         return Arena(size, dupfd.detach())
jpayne@69: 
jpayne@69:     reduction.register(Arena, reduce_arena)
jpayne@69: 
jpayne@69: #
jpayne@69: # Class allowing allocation of chunks of memory from arenas
jpayne@69: #
jpayne@69: 
jpayne@69: class Heap(object):
jpayne@69: 
jpayne@69:     # Minimum malloc() alignment
jpayne@69:     _alignment = 8
jpayne@69: 
jpayne@69:     _DISCARD_FREE_SPACE_LARGER_THAN = 4 * 1024 ** 2  # 4 MB
jpayne@69:     _DOUBLE_ARENA_SIZE_UNTIL = 4 * 1024 ** 2
jpayne@69: 
jpayne@69:     def __init__(self, size=mmap.PAGESIZE):
jpayne@69:         self._lastpid = os.getpid()
jpayne@69:         self._lock = threading.Lock()
jpayne@69:         # Current arena allocation size
jpayne@69:         self._size = size
jpayne@69:         # A sorted list of available block sizes in arenas
jpayne@69:         self._lengths = []
jpayne@69: 
jpayne@69:         # Free block management:
jpayne@69:         # - map each block size to a list of `(Arena, start, stop)` blocks
jpayne@69:         self._len_to_seq = {}
jpayne@69:         # - map `(Arena, start)` tuple to the `(Arena, start, stop)` block
jpayne@69:         #   starting at that offset
jpayne@69:         self._start_to_block = {}
jpayne@69:         # - map `(Arena, stop)` tuple to the `(Arena, start, stop)` block
jpayne@69:         #   ending at that offset
jpayne@69:         self._stop_to_block = {}
jpayne@69: 
jpayne@69:         # Map arenas to their `(Arena, start, stop)` blocks in use
jpayne@69:         self._allocated_blocks = defaultdict(set)
jpayne@69:         self._arenas = []
jpayne@69: 
jpayne@69:         # List of pending blocks to free - see comment in free() below
jpayne@69:         self._pending_free_blocks = []
jpayne@69: 
jpayne@69:         # Statistics
jpayne@69:         self._n_mallocs = 0
jpayne@69:         self._n_frees = 0
jpayne@69: 
jpayne@69:     @staticmethod
jpayne@69:     def _roundup(n, alignment):
jpayne@69:         # alignment must be a power of 2
jpayne@69:         mask = alignment - 1
jpayne@69:         return (n + mask) & ~mask
jpayne@69: 
jpayne@69:     def _new_arena(self, size):
jpayne@69:         # Create a new arena with at least the given *size*
jpayne@69:         length = self._roundup(max(self._size, size), mmap.PAGESIZE)
jpayne@69:         # We carve larger and larger arenas, for efficiency, until we
jpayne@69:         # reach a large-ish size (roughly L3 cache-sized)
jpayne@69:         if self._size < self._DOUBLE_ARENA_SIZE_UNTIL:
jpayne@69:             self._size *= 2
jpayne@69:         util.info('allocating a new mmap of length %d', length)
jpayne@69:         arena = Arena(length)
jpayne@69:         self._arenas.append(arena)
jpayne@69:         return (arena, 0, length)
jpayne@69: 
jpayne@69:     def _discard_arena(self, arena):
jpayne@69:         # Possibly delete the given (unused) arena
jpayne@69:         length = arena.size
jpayne@69:         # Reusing an existing arena is faster than creating a new one, so
jpayne@69:         # we only reclaim space if it's large enough.
jpayne@69:         if length < self._DISCARD_FREE_SPACE_LARGER_THAN:
jpayne@69:             return
jpayne@69:         blocks = self._allocated_blocks.pop(arena)
jpayne@69:         assert not blocks
jpayne@69:         del self._start_to_block[(arena, 0)]
jpayne@69:         del self._stop_to_block[(arena, length)]
jpayne@69:         self._arenas.remove(arena)
jpayne@69:         seq = self._len_to_seq[length]
jpayne@69:         seq.remove((arena, 0, length))
jpayne@69:         if not seq:
jpayne@69:             del self._len_to_seq[length]
jpayne@69:             self._lengths.remove(length)
jpayne@69: 
jpayne@69:     def _malloc(self, size):
jpayne@69:         # returns a large enough block -- it might be much larger
jpayne@69:         i = bisect.bisect_left(self._lengths, size)
jpayne@69:         if i == len(self._lengths):
jpayne@69:             return self._new_arena(size)
jpayne@69:         else:
jpayne@69:             length = self._lengths[i]
jpayne@69:             seq = self._len_to_seq[length]
jpayne@69:             block = seq.pop()
jpayne@69:             if not seq:
jpayne@69:                 del self._len_to_seq[length], self._lengths[i]
jpayne@69: 
jpayne@69:         (arena, start, stop) = block
jpayne@69:         del self._start_to_block[(arena, start)]
jpayne@69:         del self._stop_to_block[(arena, stop)]
jpayne@69:         return block
jpayne@69: 
jpayne@69:     def _add_free_block(self, block):
jpayne@69:         # make block available and try to merge with its neighbours in the arena
jpayne@69:         (arena, start, stop) = block
jpayne@69: 
jpayne@69:         try:
jpayne@69:             prev_block = self._stop_to_block[(arena, start)]
jpayne@69:         except KeyError:
jpayne@69:             pass
jpayne@69:         else:
jpayne@69:             start, _ = self._absorb(prev_block)
jpayne@69: 
jpayne@69:         try:
jpayne@69:             next_block = self._start_to_block[(arena, stop)]
jpayne@69:         except KeyError:
jpayne@69:             pass
jpayne@69:         else:
jpayne@69:             _, stop = self._absorb(next_block)
jpayne@69: 
jpayne@69:         block = (arena, start, stop)
jpayne@69:         length = stop - start
jpayne@69: 
jpayne@69:         try:
jpayne@69:             self._len_to_seq[length].append(block)
jpayne@69:         except KeyError:
jpayne@69:             self._len_to_seq[length] = [block]
jpayne@69:             bisect.insort(self._lengths, length)
jpayne@69: 
jpayne@69:         self._start_to_block[(arena, start)] = block
jpayne@69:         self._stop_to_block[(arena, stop)] = block
jpayne@69: 
jpayne@69:     def _absorb(self, block):
jpayne@69:         # deregister this block so it can be merged with a neighbour
jpayne@69:         (arena, start, stop) = block
jpayne@69:         del self._start_to_block[(arena, start)]
jpayne@69:         del self._stop_to_block[(arena, stop)]
jpayne@69: 
jpayne@69:         length = stop - start
jpayne@69:         seq = self._len_to_seq[length]
jpayne@69:         seq.remove(block)
jpayne@69:         if not seq:
jpayne@69:             del self._len_to_seq[length]
jpayne@69:             self._lengths.remove(length)
jpayne@69: 
jpayne@69:         return start, stop
jpayne@69: 
jpayne@69:     def _remove_allocated_block(self, block):
jpayne@69:         arena, start, stop = block
jpayne@69:         blocks = self._allocated_blocks[arena]
jpayne@69:         blocks.remove((start, stop))
jpayne@69:         if not blocks:
jpayne@69:             # Arena is entirely free, discard it from this process
jpayne@69:             self._discard_arena(arena)
jpayne@69: 
jpayne@69:     def _free_pending_blocks(self):
jpayne@69:         # Free all the blocks in the pending list - called with the lock held.
jpayne@69:         while True:
jpayne@69:             try:
jpayne@69:                 block = self._pending_free_blocks.pop()
jpayne@69:             except IndexError:
jpayne@69:                 break
jpayne@69:             self._add_free_block(block)
jpayne@69:             self._remove_allocated_block(block)
jpayne@69: 
jpayne@69:     def free(self, block):
jpayne@69:         # free a block returned by malloc()
jpayne@69:         # Since free() can be called asynchronously by the GC, it could happen
jpayne@69:         # that it's called while self._lock is held: in that case,
jpayne@69:         # self._lock.acquire() would deadlock (issue #12352). To avoid that, a
jpayne@69:         # trylock is used instead, and if the lock can't be acquired
jpayne@69:         # immediately, the block is added to a list of blocks to be freed
jpayne@69:         # synchronously sometimes later from malloc() or free(), by calling
jpayne@69:         # _free_pending_blocks() (appending and retrieving from a list is not
jpayne@69:         # strictly thread-safe but under CPython it's atomic thanks to the GIL).
jpayne@69:         if os.getpid() != self._lastpid:
jpayne@69:             raise ValueError(
jpayne@69:                 "My pid ({0:n}) is not last pid {1:n}".format(
jpayne@69:                     os.getpid(),self._lastpid))
jpayne@69:         if not self._lock.acquire(False):
jpayne@69:             # can't acquire the lock right now, add the block to the list of
jpayne@69:             # pending blocks to free
jpayne@69:             self._pending_free_blocks.append(block)
jpayne@69:         else:
jpayne@69:             # we hold the lock
jpayne@69:             try:
jpayne@69:                 self._n_frees += 1
jpayne@69:                 self._free_pending_blocks()
jpayne@69:                 self._add_free_block(block)
jpayne@69:                 self._remove_allocated_block(block)
jpayne@69:             finally:
jpayne@69:                 self._lock.release()
jpayne@69: 
jpayne@69:     def malloc(self, size):
jpayne@69:         # return a block of right size (possibly rounded up)
jpayne@69:         if size < 0:
jpayne@69:             raise ValueError("Size {0:n} out of range".format(size))
jpayne@69:         if sys.maxsize <= size:
jpayne@69:             raise OverflowError("Size {0:n} too large".format(size))
jpayne@69:         if os.getpid() != self._lastpid:
jpayne@69:             self.__init__()                     # reinitialize after fork
jpayne@69:         with self._lock:
jpayne@69:             self._n_mallocs += 1
jpayne@69:             # allow pending blocks to be marked available
jpayne@69:             self._free_pending_blocks()
jpayne@69:             size = self._roundup(max(size, 1), self._alignment)
jpayne@69:             (arena, start, stop) = self._malloc(size)
jpayne@69:             real_stop = start + size
jpayne@69:             if real_stop < stop:
jpayne@69:                 # if the returned block is larger than necessary, mark
jpayne@69:                 # the remainder available
jpayne@69:                 self._add_free_block((arena, real_stop, stop))
jpayne@69:             self._allocated_blocks[arena].add((start, real_stop))
jpayne@69:             return (arena, start, real_stop)
jpayne@69: 
jpayne@69: #
jpayne@69: # Class wrapping a block allocated out of a Heap -- can be inherited by child process
jpayne@69: #
jpayne@69: 
jpayne@69: class BufferWrapper(object):
jpayne@69: 
jpayne@69:     _heap = Heap()
jpayne@69: 
jpayne@69:     def __init__(self, size):
jpayne@69:         if size < 0:
jpayne@69:             raise ValueError("Size {0:n} out of range".format(size))
jpayne@69:         if sys.maxsize <= size:
jpayne@69:             raise OverflowError("Size {0:n} too large".format(size))
jpayne@69:         block = BufferWrapper._heap.malloc(size)
jpayne@69:         self._state = (block, size)
jpayne@69:         util.Finalize(self, BufferWrapper._heap.free, args=(block,))
jpayne@69: 
jpayne@69:     def create_memoryview(self):
jpayne@69:         (arena, start, stop), size = self._state
jpayne@69:         return memoryview(arena.buffer)[start:start+size]