summaryrefslogtreecommitdiffstats
path: root/Lib/multiprocessing/heap.py
blob: 7e596ca70fa78e67576e38534f265c9b94112ba7 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
#
# Module which supports allocation of memory from an mmap
#
# multiprocessing/heap.py
#
# Copyright (c) 2007-2008, R Oudkerk --- see COPYING.txt
#

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(), Arena._counter.next())
            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 = []

    @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(self, block):
        # free a block returned by malloc()
        assert os.getpid() == self._lastpid
        self._lock.acquire()
        try:
            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.maxint
        if os.getpid() != self._lastpid:
            self.__init__()                     # reinitialize after fork
        self._lock.acquire()
        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.maxint
        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]