2 * Copyright 2013 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/Portability.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 #if FOLLY_HAVE_MALLOC_H
65 #include <bits/functexcept.h>
68 * Define various ALLOCM_* macros normally provided by jemalloc. We define
69 * them so that we don't have to include jemalloc.h, in case the program is
70 * built without jemalloc support.
72 #ifndef ALLOCM_SUCCESS
74 #define ALLOCM_SUCCESS 0
75 #define ALLOCM_ERR_OOM 1
76 #define ALLOCM_ERR_NOT_MOVED 2
78 #define ALLOCM_ZERO 64
79 #define ALLOCM_NO_MOVE 128
81 #define ALLOCM_LG_ALIGN(la) (la)
83 #if defined(JEMALLOC_MANGLE) && defined(JEMALLOC_EXPERIMENTAL)
84 #define rallocm je_rallocm
85 #define allocm je_allocm
88 #endif /* ALLOCM_SUCCESS */
91 * Declare rallocm() and malloc_usable_size() as weak symbols. It
92 * will be provided by jemalloc if we are using jemalloc, or it will
93 * be NULL if we are using another malloc implementation.
95 extern "C" int rallocm(void**, size_t*, size_t, size_t, int)
96 __attribute__((weak));
97 extern "C" int allocm(void**, size_t*, size_t, int)
98 __attribute__((weak));
100 #ifdef _LIBSTDCXX_FBSTRING
101 namespace std _GLIBCXX_VISIBILITY(default) {
102 _GLIBCXX_BEGIN_NAMESPACE_VERSION
109 * Determine if we are using jemalloc or not.
111 inline bool usingJEMalloc() {
112 return rallocm != NULL;
116 * For jemalloc's size classes, see
117 * http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
119 inline size_t goodMallocSize(size_t minSize) {
120 if (!usingJEMalloc()) {
121 // Not using jemalloc - no smarts
125 // Choose smallest allocation to be 64 bytes - no tripping over
126 // cache line boundaries, and small string optimization takes care
127 // of short strings anyway.
130 if (minSize <= 512) {
131 // Round up to the next multiple of 64; we don't want to trip over
132 // cache line boundaries.
133 return (minSize + 63) & ~size_t(63);
135 if (minSize <= 3840) {
136 // Round up to the next multiple of 256
137 return (minSize + 255) & ~size_t(255);
139 if (minSize <= 4072 * 1024) {
140 // Round up to the next multiple of 4KB
141 return (minSize + 4095) & ~size_t(4095);
144 // Round up to the next multiple of 4MB
145 return (minSize + 4194303) & ~size_t(4194303);
148 // We always request "good" sizes for allocation, so jemalloc can
149 // never grow in place small blocks; they're already occupied to the
150 // brim. Blocks larger than or equal to 4096 bytes can in fact be
151 // expanded in place, and this constant reflects that.
152 static const size_t jemallocMinInPlaceExpandable = 4096;
155 * Trivial wrappers around malloc, calloc, realloc that check for allocation
156 * failure and throw std::bad_alloc in that case.
158 inline void* checkedMalloc(size_t size) {
159 void* p = malloc(size);
160 if (!p) std::__throw_bad_alloc();
164 inline void* checkedCalloc(size_t n, size_t size) {
165 void* p = calloc(n, size);
166 if (!p) std::__throw_bad_alloc();
170 inline void* checkedRealloc(void* ptr, size_t size) {
171 void* p = realloc(ptr, size);
172 if (!p) std::__throw_bad_alloc();
177 * This function tries to reallocate a buffer of which only the first
178 * currentSize bytes are used. The problem with using realloc is that
179 * if currentSize is relatively small _and_ if realloc decides it
180 * needs to move the memory chunk to a new buffer, then realloc ends
181 * up copying data that is not used. It's impossible to hook into
182 * GNU's malloc to figure whether expansion will occur in-place or as
183 * a malloc-copy-free troika. (If an expand_in_place primitive would
184 * be available, smartRealloc would use it.) As things stand, this
185 * routine just tries to call realloc() (thus benefitting of potential
186 * copy-free coalescing) unless there's too much slack memory.
188 inline void* smartRealloc(void* p,
189 const size_t currentSize,
190 const size_t currentCapacity,
191 const size_t newCapacity) {
193 assert(currentSize <= currentCapacity &&
194 currentCapacity < newCapacity);
196 if (usingJEMalloc()) {
197 // using jemalloc's API. Don't forget that jemalloc can never grow
198 // in place blocks smaller than 4096 bytes.
199 if (currentCapacity >= jemallocMinInPlaceExpandable &&
200 rallocm(&p, NULL, newCapacity, 0, ALLOCM_NO_MOVE) == ALLOCM_SUCCESS) {
201 // Managed to expand in place
204 // Cannot expand; must move
205 auto const result = checkedMalloc(newCapacity);
206 std::memcpy(result, p, currentSize);
211 // No jemalloc no honey
212 auto const slack = currentCapacity - currentSize;
213 if (slack * 2 > currentSize) {
214 // Too much slack, malloc-copy-free cycle:
215 auto const result = checkedMalloc(newCapacity);
216 std::memcpy(result, p, currentSize);
220 // If there's not too much slack, we realloc in hope of coalescing
221 return checkedRealloc(p, newCapacity);
224 #ifdef _LIBSTDCXX_FBSTRING
225 _GLIBCXX_END_NAMESPACE_VERSION
230 #endif // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
232 #endif // FOLLY_MALLOC_H_