2 * Copyright 2012 Facebook, Inc.
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
8 * http://www.apache.org/licenses/LICENSE-2.0
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.
17 // Functions to provide smarter use of jemalloc, if jemalloc is being used.
18 // http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
20 #ifndef FOLLY_MALLOC_H_
21 #define FOLLY_MALLOC_H_
23 // If using fbstring from libstdc++, then just define stub code
24 // here to typedef the fbstring type into the folly namespace.
25 // This provides backwards compatibility for code that explicitly
26 // includes and uses fbstring.
27 #if defined(_GLIBCXX_USE_FB) && !defined(_LIBSTDCXX_FBSTRING)
31 using std::goodMallocSize;
32 using std::jemallocMinInPlaceExpandable;
33 using std::usingJEMalloc;
34 using std::smartRealloc;
35 using std::checkedMalloc;
36 using std::checkedCalloc;
37 using std::checkedRealloc;
40 #else // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
42 #ifdef _LIBSTDCXX_FBSTRING
43 #pragma GCC system_header
44 #define FOLLY_HAVE_MALLOC_H 1
46 #include "folly-config.h"
49 // for malloc_usable_size
50 // NOTE: FreeBSD 9 doesn't have malloc.h. It's defitions
51 // are found in stdlib.h.
52 #ifdef FOLLY_HAVE_MALLOC_H
65 #include <bits/functexcept.h>
68 * Declare rallocm() and malloc_usable_size() as weak symbols. It
69 * will be provided by jemalloc if we are using jemalloc, or it will
70 * be NULL if we are using another malloc implementation.
72 extern "C" int rallocm(void**, size_t*, size_t, size_t, int)
73 __attribute__((weak));
76 * Define the ALLOCM_SUCCESS, ALLOCM_ZERO, and ALLOCM_NO_MOVE constants
77 * normally provided by jemalloc. We define them so that we don't have to
78 * include jemalloc.h, in case the program is built without jemalloc support.
80 #ifndef ALLOCM_SUCCESS
81 #define ALLOCM_SUCCESS 0
82 #define ALLOCM_ERR_OOM 1
83 #define ALLOCM_ERR_NOT_MOVED 2
85 #define ALLOCM_ZERO 64
86 #define ALLOCM_NO_MOVE 128
87 #define ALLOCM_LG_ALIGN(la) (la)
90 #ifdef _LIBSTDCXX_FBSTRING
91 namespace std _GLIBCXX_VISIBILITY(default) {
92 _GLIBCXX_BEGIN_NAMESPACE_VERSION
99 * Determine if we are using jemalloc or not.
101 inline bool usingJEMalloc() {
102 return rallocm != NULL;
106 * For jemalloc's size classes, see
107 * http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
109 inline size_t goodMallocSize(size_t minSize) {
110 if (!usingJEMalloc()) {
111 // Not using jemalloc - no smarts
115 // Choose smallest allocation to be 64 bytes - no tripping over
116 // cache line boundaries, and small string optimization takes care
117 // of short strings anyway.
120 if (minSize <= 512) {
121 // Round up to the next multiple of 64; we don't want to trip over
122 // cache line boundaries.
123 return (minSize + 63) & ~size_t(63);
125 if (minSize <= 3840) {
126 // Round up to the next multiple of 256
127 return (minSize + 255) & ~size_t(255);
129 if (minSize <= 4072 * 1024) {
130 // Round up to the next multiple of 4KB
131 return (minSize + 4095) & ~size_t(4095);
134 // Round up to the next multiple of 4MB
135 return (minSize + 4194303) & ~size_t(4194303);
138 // We always request "good" sizes for allocation, so jemalloc can
139 // never grow in place small blocks; they're already occupied to the
140 // brim. Blocks larger than or equal to 4096 bytes can in fact be
141 // expanded in place, and this constant reflects that.
142 static const size_t jemallocMinInPlaceExpandable = 4096;
145 * Trivial wrappers around malloc, calloc, realloc that check for allocation
146 * failure and throw std::bad_alloc in that case.
148 inline void* checkedMalloc(size_t size) {
149 void* p = malloc(size);
150 if (!p) std::__throw_bad_alloc();
154 inline void* checkedCalloc(size_t n, size_t size) {
155 void* p = calloc(n, size);
156 if (!p) std::__throw_bad_alloc();
160 inline void* checkedRealloc(void* ptr, size_t size) {
161 void* p = realloc(ptr, size);
162 if (!p) std::__throw_bad_alloc();
167 * This function tries to reallocate a buffer of which only the first
168 * currentSize bytes are used. The problem with using realloc is that
169 * if currentSize is relatively small _and_ if realloc decides it
170 * needs to move the memory chunk to a new buffer, then realloc ends
171 * up copying data that is not used. It's impossible to hook into
172 * GNU's malloc to figure whether expansion will occur in-place or as
173 * a malloc-copy-free troika. (If an expand_in_place primitive would
174 * be available, smartRealloc would use it.) As things stand, this
175 * routine just tries to call realloc() (thus benefitting of potential
176 * copy-free coalescing) unless there's too much slack memory.
178 inline void* smartRealloc(void* p,
179 const size_t currentSize,
180 const size_t currentCapacity,
181 const size_t newCapacity) {
183 assert(currentSize <= currentCapacity &&
184 currentCapacity < newCapacity);
186 if (usingJEMalloc()) {
187 // using jemalloc's API. Don't forget that jemalloc can never grow
188 // in place blocks smaller than 4096 bytes.
189 if (currentCapacity >= jemallocMinInPlaceExpandable &&
190 rallocm(&p, NULL, newCapacity, 0, ALLOCM_NO_MOVE) == ALLOCM_SUCCESS) {
191 // Managed to expand in place
194 // Cannot expand; must move
195 auto const result = checkedMalloc(newCapacity);
196 std::memcpy(result, p, currentSize);
201 // No jemalloc no honey
202 auto const slack = currentCapacity - currentSize;
203 if (slack * 2 > currentSize) {
204 // Too much slack, malloc-copy-free cycle:
205 auto const result = checkedMalloc(newCapacity);
206 std::memcpy(result, p, currentSize);
210 // If there's not too much slack, we realloc in hope of coalescing
211 return checkedRealloc(p, newCapacity);
214 #ifdef _LIBSTDCXX_FBSTRING
215 _GLIBCXX_END_NAMESPACE_VERSION
220 #endif // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
222 #endif // FOLLY_MALLOC_H_