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/*
* Copyright 2015 Facebook, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
// Functions to provide smarter use of jemalloc, if jemalloc is being used.
// http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
#ifndef FOLLY_MALLOC_H_
#define FOLLY_MALLOC_H_
/**
* Define various MALLOCX_* macros normally provided by jemalloc. We define
* them so that we don't have to include jemalloc.h, in case the program is
* built without jemalloc support.
*/
#ifndef MALLOCX_LG_ALIGN
#define MALLOCX_LG_ALIGN(la) (la)
#endif
#ifndef MALLOCX_ZERO
#define MALLOCX_ZERO (static_cast<int>(0x40))
#endif
// If using fbstring from libstdc++, then just define stub code
// here to typedef the fbstring type into the folly namespace.
// This provides backwards compatibility for code that explicitly
// includes and uses fbstring.
#if defined(_GLIBCXX_USE_FB) && !defined(_LIBSTDCXX_FBSTRING)
#include <folly/detail/Malloc.h>
#include <string>
namespace folly {
using std::goodMallocSize;
using std::jemallocMinInPlaceExpandable;
using std::usingJEMalloc;
using std::smartRealloc;
using std::checkedMalloc;
using std::checkedCalloc;
using std::checkedRealloc;
}
#else // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
#ifdef _LIBSTDCXX_FBSTRING
#pragma GCC system_header
/**
* Declare *allocx() and mallctl*() as weak symbols. These will be provided by
* jemalloc if we are using jemalloc, or will be NULL if we are using another
* malloc implementation.
*/
extern "C" void* mallocx(size_t, int)
__attribute__((__weak__));
extern "C" void* rallocx(void*, size_t, int)
__attribute__((__weak__));
extern "C" size_t xallocx(void*, size_t, size_t, int)
__attribute__((__weak__));
extern "C" size_t sallocx(const void*, int)
__attribute__((__weak__));
extern "C" void dallocx(void*, int)
__attribute__((__weak__));
extern "C" size_t nallocx(size_t, int)
__attribute__((__weak__));
extern "C" int mallctl(const char*, void*, size_t*, void*, size_t)
__attribute__((__weak__));
extern "C" int mallctlnametomib(const char*, size_t*, size_t*)
__attribute__((__weak__));
extern "C" int mallctlbymib(const size_t*, size_t, void*, size_t*, void*,
size_t)
__attribute__((__weak__));
#include <bits/functexcept.h>
#define FOLLY_HAVE_MALLOC_H 1
#else
#include <folly/detail/Malloc.h> /* nolint */
#include <folly/Portability.h>
#endif
// for malloc_usable_size
// NOTE: FreeBSD 9 doesn't have malloc.h. It's defitions
// are found in stdlib.h.
#if FOLLY_HAVE_MALLOC_H
#include <malloc.h>
#else
#include <stdlib.h>
#endif
#include <cassert>
#include <cstddef>
#include <cstdlib>
#include <cstring>
#include <new>
#ifdef _LIBSTDCXX_FBSTRING
namespace std _GLIBCXX_VISIBILITY(default) {
_GLIBCXX_BEGIN_NAMESPACE_VERSION
#else
namespace folly {
#endif
bool usingJEMallocSlow();
/**
* Determine if we are using jemalloc or not.
*/
inline bool usingJEMalloc() {
// Checking for rallocx != NULL is not sufficient; we may be in a dlopen()ed
// module that depends on libjemalloc, so rallocx is resolved, but the main
// program might be using a different memory allocator. Look at the
// implementation of usingJEMallocSlow() for the (hacky) details.
static const bool result = usingJEMallocSlow();
return result;
}
/**
* For jemalloc's size classes, see
* http://www.canonware.com/download/jemalloc/jemalloc-latest/doc/jemalloc.html
*/
inline size_t goodMallocSize(size_t minSize) noexcept {
if (!usingJEMalloc()) {
// Not using jemalloc - no smarts
return minSize;
}
size_t goodSize;
if (minSize <= 64) {
// Choose smallest allocation to be 64 bytes - no tripping over
// cache line boundaries, and small string optimization takes care
// of short strings anyway.
goodSize = 64;
} else if (minSize <= 512) {
// Round up to the next multiple of 64; we don't want to trip over
// cache line boundaries.
goodSize = (minSize + 63) & ~size_t(63);
} else {
// Boundaries between size classes depend on numerious factors, some of
// which can even be modified at run-time. Determine the good allocation
// size by calling nallocx() directly.
goodSize = nallocx(minSize, 0);
}
assert(nallocx(goodSize, 0) == goodSize);
return goodSize;
}
// We always request "good" sizes for allocation, so jemalloc can
// never grow in place small blocks; they're already occupied to the
// brim. Blocks larger than or equal to 4096 bytes can in fact be
// expanded in place, and this constant reflects that.
static const size_t jemallocMinInPlaceExpandable = 4096;
/**
* Trivial wrappers around malloc, calloc, realloc that check for allocation
* failure and throw std::bad_alloc in that case.
*/
inline void* checkedMalloc(size_t size) {
void* p = malloc(size);
if (!p) std::__throw_bad_alloc();
return p;
}
inline void* checkedCalloc(size_t n, size_t size) {
void* p = calloc(n, size);
if (!p) std::__throw_bad_alloc();
return p;
}
inline void* checkedRealloc(void* ptr, size_t size) {
void* p = realloc(ptr, size);
if (!p) std::__throw_bad_alloc();
return p;
}
/**
* This function tries to reallocate a buffer of which only the first
* currentSize bytes are used. The problem with using realloc is that
* if currentSize is relatively small _and_ if realloc decides it
* needs to move the memory chunk to a new buffer, then realloc ends
* up copying data that is not used. It's impossible to hook into
* GNU's malloc to figure whether expansion will occur in-place or as
* a malloc-copy-free troika. (If an expand_in_place primitive would
* be available, smartRealloc would use it.) As things stand, this
* routine just tries to call realloc() (thus benefitting of potential
* copy-free coalescing) unless there's too much slack memory.
*/
inline void* smartRealloc(void* p,
const size_t currentSize,
const size_t currentCapacity,
const size_t newCapacity) {
assert(p);
assert(currentSize <= currentCapacity &&
currentCapacity < newCapacity);
if (usingJEMalloc()) {
// using jemalloc's API. Don't forget that jemalloc can never grow
// in place blocks smaller than 4096 bytes.
//
// NB: newCapacity may not be precisely equal to a jemalloc size class,
// i.e. newCapacity is not guaranteed to be the result of a
// goodMallocSize() call, therefore xallocx() may return more than
// newCapacity bytes of space. Use >= rather than == to check whether
// xallocx() successfully expanded in place.
if (currentCapacity >= jemallocMinInPlaceExpandable &&
xallocx(p, newCapacity, 0, 0) >= newCapacity) {
// Managed to expand in place
return p;
}
// Cannot expand; must move
auto const result = checkedMalloc(newCapacity);
std::memcpy(result, p, currentSize);
free(p);
return result;
}
// No jemalloc no honey
auto const slack = currentCapacity - currentSize;
if (slack * 2 > currentSize) {
// Too much slack, malloc-copy-free cycle:
auto const result = checkedMalloc(newCapacity);
std::memcpy(result, p, currentSize);
free(p);
return result;
}
// If there's not too much slack, we realloc in hope of coalescing
return checkedRealloc(p, newCapacity);
}
#ifdef _LIBSTDCXX_FBSTRING
_GLIBCXX_END_NAMESPACE_VERSION
#endif
} // folly
#endif // !defined(_GLIBCXX_USE_FB) || defined(_LIBSTDCXX_FBSTRING)
#endif // FOLLY_MALLOC_H_