1 | /* |
2 | * Copyright 2015-present Facebook, Inc. |
3 | * |
4 | * Licensed under the Apache License, Version 2.0 (the "License"); |
5 | * you may not use this file except in compliance with the License. |
6 | * You may obtain a copy of the License at |
7 | * |
8 | * http://www.apache.org/licenses/LICENSE-2.0 |
9 | * |
10 | * Unless required by applicable law or agreed to in writing, software |
11 | * distributed under the License is distributed on an "AS IS" BASIS, |
12 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
13 | * See the License for the specific language governing permissions and |
14 | * limitations under the License. |
15 | */ |
16 | |
17 | #pragma once |
18 | |
19 | #include <atomic> |
20 | #include <cassert> |
21 | #include <cstdint> |
22 | #include <system_error> |
23 | |
24 | #include <folly/portability/SysMman.h> |
25 | #include <folly/portability/Unistd.h> |
26 | |
27 | namespace folly { |
28 | namespace detail { |
29 | |
30 | class MMapAlloc { |
31 | private: |
32 | size_t computeSize(size_t size) { |
33 | long pagesize = sysconf(_SC_PAGESIZE); |
34 | size_t mmapLength = ((size - 1) & ~(pagesize - 1)) + pagesize; |
35 | assert(size <= mmapLength && mmapLength < size + pagesize); |
36 | assert((mmapLength % pagesize) == 0); |
37 | return mmapLength; |
38 | } |
39 | |
40 | public: |
41 | void* allocate(size_t size) { |
42 | auto len = computeSize(size); |
43 | |
44 | int = 0; |
45 | #if defined(MAP_POPULATE) |
46 | extraflags |= MAP_POPULATE; |
47 | #endif |
48 | // MAP_HUGETLB is a perf win, but requires cooperation from the |
49 | // deployment environment (and a change to computeSize()). |
50 | void* mem = static_cast<void*>(mmap( |
51 | nullptr, |
52 | len, |
53 | PROT_READ | PROT_WRITE, |
54 | MAP_PRIVATE | MAP_ANONYMOUS | extraflags, |
55 | -1, |
56 | 0)); |
57 | if (mem == reinterpret_cast<void*>(-1)) { |
58 | throw std::system_error(errno, std::system_category()); |
59 | } |
60 | #if !defined(MAP_POPULATE) && defined(MADV_WILLNEED) |
61 | madvise(mem, size, MADV_WILLNEED); |
62 | #endif |
63 | |
64 | return mem; |
65 | } |
66 | |
67 | void deallocate(void* p, size_t size) { |
68 | auto len = computeSize(size); |
69 | munmap(p, len); |
70 | } |
71 | }; |
72 | |
73 | template <typename Allocator> |
74 | struct GivesZeroFilledMemory : public std::false_type {}; |
75 | |
76 | template <> |
77 | struct GivesZeroFilledMemory<MMapAlloc> : public std::true_type {}; |
78 | |
79 | } // namespace detail |
80 | } // namespace folly |
81 | |