2 * Copyright 2014 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_
24 * Define various MALLOCX_* macros normally provided by jemalloc. We define
25 * them so that we don't have to include jemalloc.h, in case the program is
26 * built without jemalloc support.
28 #ifndef MALLOCX_LG_ALIGN
29 #define MALLOCX_LG_ALIGN(la) (la)
32 #define MALLOCX_ZERO (static_cast<int>(0x40))
35 // If using fbstring from libstdc++, then just define stub code
36 // here to typedef the fbstring type into the folly namespace.
37 // This provides backwards compatibility for code that explicitly
38 // includes and uses fbstring.
39 #if defined(_GLIBCXX_USE_FB) && !defined(_LIBSTDCXX_FBSTRING)
41 #include <folly/detail/Malloc.h>
46 using std::goodMallocSize;
47 using std::jemallocMinInPlaceExpandable;
48 using std::usingJEMalloc;
49 using std::smartRealloc;
50 using std::checkedMalloc;
51 using std::checkedCalloc;
52 using std::checkedRealloc;
55 #else // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
57 #ifdef _LIBSTDCXX_FBSTRING
58 #pragma GCC system_header
61 * Declare *allocx() and mallctl() as weak symbols. These will be provided by
62 * jemalloc if we are using jemalloc, or will be NULL if we are using another
63 * malloc implementation.
65 extern "C" void* mallocx(size_t, int)
66 __attribute__((__weak__));
67 extern "C" void* rallocx(void*, size_t, int)
68 __attribute__((__weak__));
69 extern "C" size_t xallocx(void*, size_t, size_t, int)
70 __attribute__((__weak__));
71 extern "C" size_t sallocx(const void*, int)
72 __attribute__((__weak__));
73 extern "C" void dallocx(void*, int)
74 __attribute__((__weak__));
75 extern "C" size_t nallocx(size_t, int)
76 __attribute__((__weak__));
77 extern "C" int mallctl(const char*, void*, size_t*, void*, size_t)
78 __attribute__((__weak__));
80 #include <bits/functexcept.h>
81 #define FOLLY_HAVE_MALLOC_H 1
83 #include <folly/detail/Malloc.h> /* nolint */
84 #include <folly/Portability.h>
87 // for malloc_usable_size
88 // NOTE: FreeBSD 9 doesn't have malloc.h. It's defitions
89 // are found in stdlib.h.
90 #if FOLLY_HAVE_MALLOC_H
103 #ifdef _LIBSTDCXX_FBSTRING
104 namespace std _GLIBCXX_VISIBILITY(default) {
105 _GLIBCXX_BEGIN_NAMESPACE_VERSION
110 bool usingJEMallocSlow();
113 * Determine if we are using jemalloc or not.
115 inline bool usingJEMalloc() {
116 // Checking for rallocx != NULL is not sufficient; we may be in a dlopen()ed
117 // module that depends on libjemalloc, so rallocx is resolved, but the main
118 // program might be using a different memory allocator. Look at the
119 // implementation of usingJEMallocSlow() for the (hacky) details.
120 static const bool result = usingJEMallocSlow();
125 * For jemalloc's size classes, see
126 * http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
128 inline size_t goodMallocSize(size_t minSize) noexcept {
129 if (!usingJEMalloc()) {
130 // Not using jemalloc - no smarts
135 // Choose smallest allocation to be 64 bytes - no tripping over
136 // cache line boundaries, and small string optimization takes care
137 // of short strings anyway.
139 } else if (minSize <= 512) {
140 // Round up to the next multiple of 64; we don't want to trip over
141 // cache line boundaries.
142 goodSize = (minSize + 63) & ~size_t(63);
144 // Boundaries between size classes depend on numerious factors, some of
145 // which can even be modified at run-time. Determine the good allocation
146 // size by calling nallocx() directly.
147 goodSize = nallocx(minSize, 0);
149 assert(nallocx(goodSize, 0) == goodSize);
153 // We always request "good" sizes for allocation, so jemalloc can
154 // never grow in place small blocks; they're already occupied to the
155 // brim. Blocks larger than or equal to 4096 bytes can in fact be
156 // expanded in place, and this constant reflects that.
157 static const size_t jemallocMinInPlaceExpandable = 4096;
160 * Trivial wrappers around malloc, calloc, realloc that check for allocation
161 * failure and throw std::bad_alloc in that case.
163 inline void* checkedMalloc(size_t size) {
164 void* p = malloc(size);
165 if (!p) std::__throw_bad_alloc();
169 inline void* checkedCalloc(size_t n, size_t size) {
170 void* p = calloc(n, size);
171 if (!p) std::__throw_bad_alloc();
175 inline void* checkedRealloc(void* ptr, size_t size) {
176 void* p = realloc(ptr, size);
177 if (!p) std::__throw_bad_alloc();
182 * This function tries to reallocate a buffer of which only the first
183 * currentSize bytes are used. The problem with using realloc is that
184 * if currentSize is relatively small _and_ if realloc decides it
185 * needs to move the memory chunk to a new buffer, then realloc ends
186 * up copying data that is not used. It's impossible to hook into
187 * GNU's malloc to figure whether expansion will occur in-place or as
188 * a malloc-copy-free troika. (If an expand_in_place primitive would
189 * be available, smartRealloc would use it.) As things stand, this
190 * routine just tries to call realloc() (thus benefitting of potential
191 * copy-free coalescing) unless there's too much slack memory.
193 inline void* smartRealloc(void* p,
194 const size_t currentSize,
195 const size_t currentCapacity,
196 const size_t newCapacity) {
198 assert(currentSize <= currentCapacity &&
199 currentCapacity < newCapacity);
201 if (usingJEMalloc()) {
202 // using jemalloc's API. Don't forget that jemalloc can never grow
203 // in place blocks smaller than 4096 bytes.
205 // NB: newCapacity may not be precisely equal to a jemalloc size class,
206 // i.e. newCapacity is not guaranteed to be the result of a
207 // goodMallocSize() call, therefore xallocx() may return more than
208 // newCapacity bytes of space. Use >= rather than == to check whether
209 // xallocx() successfully expanded in place.
210 if (currentCapacity >= jemallocMinInPlaceExpandable &&
211 xallocx(p, newCapacity, 0, 0) >= newCapacity) {
212 // Managed to expand in place
215 // Cannot expand; must move
216 auto const result = checkedMalloc(newCapacity);
217 std::memcpy(result, p, currentSize);
222 // No jemalloc no honey
223 auto const slack = currentCapacity - currentSize;
224 if (slack * 2 > currentSize) {
225 // Too much slack, malloc-copy-free cycle:
226 auto const result = checkedMalloc(newCapacity);
227 std::memcpy(result, p, currentSize);
231 // If there's not too much slack, we realloc in hope of coalescing
232 return checkedRealloc(p, newCapacity);
235 #ifdef _LIBSTDCXX_FBSTRING
236 _GLIBCXX_END_NAMESPACE_VERSION
241 #endif // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
243 #endif // FOLLY_MALLOC_H_