2 * Copyright 2017 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
22 #include <folly/portability/Config.h>
25 * Define various MALLOCX_* macros normally provided by jemalloc. We define
26 * them so that we don't have to include jemalloc.h, in case the program is
27 * built without jemalloc support.
29 #if defined(USE_JEMALLOC) || defined(FOLLY_USE_JEMALLOC)
30 // We have JEMalloc, so use it.
31 # include <jemalloc/jemalloc.h>
33 # ifndef MALLOCX_LG_ALIGN
34 # define MALLOCX_LG_ALIGN(la) (la)
37 # define MALLOCX_ZERO (static_cast<int>(0x40))
41 // If using fbstring from libstdc++ (see comment in FBString.h), then
42 // just define stub code here to typedef the fbstring type into the
44 // This provides backwards compatibility for code that explicitly
45 // includes and uses fbstring.
46 #if defined(_GLIBCXX_USE_FB) && !defined(_LIBSTDCXX_FBSTRING)
48 #include <folly/memory/detail/MallocImpl.h>
49 #include <folly/portability/BitsFunctexcept.h>
54 using std::goodMallocSize;
55 using std::jemallocMinInPlaceExpandable;
56 using std::usingJEMalloc;
57 using std::smartRealloc;
58 using std::checkedMalloc;
59 using std::checkedCalloc;
60 using std::checkedRealloc;
63 #else // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
65 #ifdef _LIBSTDCXX_FBSTRING
66 #pragma GCC system_header
69 * Declare *allocx() and mallctl*() as weak symbols. These will be provided by
70 * jemalloc if we are using jemalloc, or will be nullptr if we are using another
71 * malloc implementation.
73 extern "C" void* mallocx(size_t, int)
74 __attribute__((__weak__));
75 extern "C" void* rallocx(void*, size_t, int)
76 __attribute__((__weak__));
77 extern "C" size_t xallocx(void*, size_t, size_t, int)
78 __attribute__((__weak__));
79 extern "C" size_t sallocx(const void*, int)
80 __attribute__((__weak__));
81 extern "C" void dallocx(void*, int)
82 __attribute__((__weak__));
83 extern "C" void sdallocx(void*, size_t, int)
84 __attribute__((__weak__));
85 extern "C" size_t nallocx(size_t, int)
86 __attribute__((__weak__));
87 extern "C" int mallctl(const char*, void*, size_t*, void*, size_t)
88 __attribute__((__weak__));
89 extern "C" int mallctlnametomib(const char*, size_t*, size_t*)
90 __attribute__((__weak__));
91 extern "C" int mallctlbymib(const size_t*, size_t, void*, size_t*, void*,
93 __attribute__((__weak__));
95 #include <bits/functexcept.h>
97 #define FOLLY_HAVE_MALLOC_H 1
99 #else // !defined(_LIBSTDCXX_FBSTRING)
101 #include <folly/memory/detail/MallocImpl.h> /* nolint */
102 #include <folly/portability/BitsFunctexcept.h> /* nolint */
106 // for malloc_usable_size
107 // NOTE: FreeBSD 9 doesn't have malloc.h. Its definitions
108 // are found in stdlib.h.
109 #if FOLLY_HAVE_MALLOC_H
124 #ifdef _LIBSTDCXX_FBSTRING
125 namespace std _GLIBCXX_VISIBILITY(default) {
126 _GLIBCXX_BEGIN_NAMESPACE_VERSION
131 // Cannot depend on Portability.h when _LIBSTDCXX_FBSTRING.
132 #if defined(__GNUC__)
133 #define FOLLY_MALLOC_NOINLINE __attribute__((__noinline__))
134 #if (__GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL) >= 40900
135 // This is for checked malloc-like functions (returns non-null pointer
136 // which cannot alias any outstanding pointer).
137 #define FOLLY_MALLOC_CHECKED_MALLOC \
138 __attribute__((__returns_nonnull__, __malloc__))
140 #define FOLLY_MALLOC_CHECKED_MALLOC __attribute__((__malloc__))
143 #define FOLLY_MALLOC_NOINLINE
144 #define FOLLY_MALLOC_CHECKED_MALLOC
148 * Determine if we are using jemalloc or not.
151 inline bool usingJEMalloc() noexcept {
155 FOLLY_MALLOC_NOINLINE inline bool usingJEMalloc() noexcept {
156 // Checking for rallocx != nullptr is not sufficient; we may be in a
157 // dlopen()ed module that depends on libjemalloc, so rallocx is resolved, but
158 // the main program might be using a different memory allocator.
159 // How do we determine that we're using jemalloc? In the hackiest
160 // way possible. We allocate memory using malloc() and see if the
161 // per-thread counter of allocated memory increases. This makes me
162 // feel dirty inside. Also note that this requires jemalloc to have
163 // been compiled with --enable-stats.
164 static const bool result = [] () noexcept {
165 // Some platforms (*cough* OSX *cough*) require weak symbol checks to be
166 // in the form if (mallctl != nullptr). Not if (mallctl) or if (!mallctl)
167 // (!!). http://goo.gl/xpmctm
168 if (mallocx == nullptr || rallocx == nullptr || xallocx == nullptr
169 || sallocx == nullptr || dallocx == nullptr || sdallocx == nullptr
170 || nallocx == nullptr || mallctl == nullptr
171 || mallctlnametomib == nullptr || mallctlbymib == nullptr) {
175 // "volatile" because gcc optimizes out the reads from *counter, because
176 // it "knows" malloc doesn't modify global state...
177 /* nolint */ volatile uint64_t* counter;
178 size_t counterLen = sizeof(uint64_t*);
180 if (mallctl("thread.allocatedp", static_cast<void*>(&counter), &counterLen,
185 if (counterLen != sizeof(uint64_t*)) {
189 uint64_t origAllocated = *counter;
191 static const void* volatile ptr = malloc(1);
193 // wtf, failing to allocate 1 byte
197 return (origAllocated != *counter);
204 inline size_t goodMallocSize(size_t minSize) noexcept {
209 if (!usingJEMalloc()) {
210 // Not using jemalloc - no smarts
214 return nallocx(minSize, 0);
217 // We always request "good" sizes for allocation, so jemalloc can
218 // never grow in place small blocks; they're already occupied to the
219 // brim. Blocks larger than or equal to 4096 bytes can in fact be
220 // expanded in place, and this constant reflects that.
221 static const size_t jemallocMinInPlaceExpandable = 4096;
224 * Trivial wrappers around malloc, calloc, realloc that check for allocation
225 * failure and throw std::bad_alloc in that case.
227 inline void* checkedMalloc(size_t size) {
228 void* p = malloc(size);
230 std::__throw_bad_alloc();
235 inline void* checkedCalloc(size_t n, size_t size) {
236 void* p = calloc(n, size);
238 std::__throw_bad_alloc();
243 inline void* checkedRealloc(void* ptr, size_t size) {
244 void* p = realloc(ptr, size);
246 std::__throw_bad_alloc();
252 * This function tries to reallocate a buffer of which only the first
253 * currentSize bytes are used. The problem with using realloc is that
254 * if currentSize is relatively small _and_ if realloc decides it
255 * needs to move the memory chunk to a new buffer, then realloc ends
256 * up copying data that is not used. It's generally not a win to try
257 * to hook in to realloc() behavior to avoid copies - at least in
258 * jemalloc, realloc() almost always ends up doing a copy, because
259 * there is little fragmentation / slack space to take advantage of.
261 FOLLY_MALLOC_CHECKED_MALLOC FOLLY_MALLOC_NOINLINE inline void* smartRealloc(
263 const size_t currentSize,
264 const size_t currentCapacity,
265 const size_t newCapacity) {
267 assert(currentSize <= currentCapacity &&
268 currentCapacity < newCapacity);
270 auto const slack = currentCapacity - currentSize;
271 if (slack * 2 > currentSize) {
272 // Too much slack, malloc-copy-free cycle:
273 auto const result = checkedMalloc(newCapacity);
274 std::memcpy(result, p, currentSize);
278 // If there's not too much slack, we realloc in hope of coalescing
279 return checkedRealloc(p, newCapacity);
282 #ifdef _LIBSTDCXX_FBSTRING
283 _GLIBCXX_END_NAMESPACE_VERSION
288 #endif // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)