1/*
2 * Copyright 2016-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// http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
18
19#pragma once
20
21#include <folly/CPortability.h>
22#include <folly/portability/Config.h>
23
24#if defined(FOLLY_USE_JEMALLOC) && !FOLLY_SANITIZE
25
26#include <folly/portability/SysMman.h>
27#include <jemalloc/jemalloc.h>
28
29#if (JEMALLOC_VERSION_MAJOR > 3) && defined(MADV_DONTDUMP)
30#define FOLLY_JEMALLOC_NODUMP_ALLOCATOR_SUPPORTED 1
31#if (JEMALLOC_VERSION_MAJOR == 4)
32#define FOLLY_JEMALLOC_NODUMP_ALLOCATOR_CHUNK
33#define JEMALLOC_CHUNK_OR_EXTENT chunk
34#else
35#define FOLLY_JEMALLOC_NODUMP_ALLOCATOR_EXTENT
36#define JEMALLOC_CHUNK_OR_EXTENT extent
37#endif
38#endif
39
40#endif // FOLLY_USE_JEMALLOC
41
42#include <cstddef>
43
44namespace folly {
45
46/**
47 * An allocator which uses Jemalloc to create an dedicated arena to allocate
48 * memory from. The only special property set on the allocated memory is that
49 * the memory is not dump-able.
50 *
51 * This is done by setting MADV_DONTDUMP using the `madvise` system call. A
52 * custom hook installed which is called when allocating a new chunk / extent of
53 * memory. All it does is call the original jemalloc hook to allocate the
54 * memory and then set the advise on it before returning the pointer to the
55 * allocated memory. Jemalloc does not use allocated chunks / extents across
56 * different arenas, without `munmap`-ing them first, and the advises are not
57 * sticky i.e. they are unset if `munmap` is done. Also this arena can't be used
58 * by any other part of the code by just calling `malloc`.
59 *
60 * If target system doesn't support MADV_DONTDUMP or jemalloc doesn't support
61 * custom arena hook, JemallocNodumpAllocator would fall back to using malloc /
62 * free. Such behavior can be identified by using
63 * !defined(FOLLY_JEMALLOC_NODUMP_ALLOCATOR_SUPPORTED).
64 *
65 * Similarly, if binary isn't linked with jemalloc, the logic would fall back to
66 * malloc / free.
67 */
68class JemallocNodumpAllocator {
69 public:
70 enum class State {
71 ENABLED,
72 DISABLED,
73 };
74
75 // To be used as IOBuf::FreeFunction, userData should be set to
76 // reinterpret_cast<void*>(getFlags()).
77 static void deallocate(void* p, void* userData);
78
79 explicit JemallocNodumpAllocator(State state = State::ENABLED);
80
81 void* allocate(size_t size);
82 void* reallocate(void* p, size_t size);
83 void deallocate(void* p, size_t = 0);
84
85 unsigned getArenaIndex() const {
86 return arena_index_;
87 }
88 int getFlags() const {
89 return flags_;
90 }
91
92 private:
93#ifdef FOLLY_JEMALLOC_NODUMP_ALLOCATOR_SUPPORTED
94#ifdef FOLLY_JEMALLOC_NODUMP_ALLOCATOR_CHUNK
95 static chunk_alloc_t* original_alloc_;
96 static void* alloc(
97 void* chunk,
98#else
99 static extent_hooks_t extent_hooks_;
100 static extent_alloc_t* original_alloc_;
101 static void* alloc(
102 extent_hooks_t* extent,
103 void* new_addr,
104#endif
105 size_t size,
106 size_t alignment,
107 bool* zero,
108 bool* commit,
109 unsigned arena_ind);
110#endif // FOLLY_JEMALLOC_NODUMP_ALLOCATOR_SUPPORTED
111
112 bool extend_and_setup_arena();
113
114 unsigned arena_index_{0};
115 int flags_{0};
116};
117
118/**
119 * JemallocNodumpAllocator singleton.
120 */
121JemallocNodumpAllocator& globalJemallocNodumpAllocator();
122
123} // namespace folly
124