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// -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
// Copyright (c) 2008, Google Inc.
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above
// copyright notice, this list of conditions and the following disclaimer
// in the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google Inc. nor the names of its
// contributors may be used to endorse or promote products derived from
// this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
// ---
// Author: Sanjay Ghemawat <opensource@google.com>
#ifndef TCMALLOC_PAGE_HEAP_ALLOCATOR_H_
#define TCMALLOC_PAGE_HEAP_ALLOCATOR_H_
#include <stddef.h> // for size_t
#include "common.h" // for MetaDataAlloc
#include "internal_logging.h" // for ASSERT
namespace tcmalloc {
// Simple allocator for objects of a specified type. External locking
// is required before accessing one of these objects.
template <class T>
class PageHeapAllocator {
public:
constexpr PageHeapAllocator() = default;
// We use an explicit Init function because these variables are statically
// allocated and their constructors might not have run by the time some
// other static variable tries to allocate memory.
void Init() {
ASSERT(sizeof(T) <= kAllocIncrement);
inuse_ = 0;
free_area_ = nullptr;
free_avail_ = 0;
free_list_ = nullptr;
// Reserve some space at the beginning to avoid fragmentation.
Delete(New());
}
T* New() {
// Consult free list
void* result;
if (free_list_ != nullptr) {
result = free_list_;
free_list_ = *(reinterpret_cast<void**>(result));
} else {
if (free_avail_ < sizeof(T)) {
// Need more room. We assume that MetaDataAlloc returns
// suitably aligned memory.
free_area_ = reinterpret_cast<char*>(MetaDataAlloc(kAllocIncrement));
if (free_area_ == nullptr) {
Log(kCrash, __FILE__, __LINE__,
"FATAL ERROR: Out of memory trying to allocate internal "
"tcmalloc data (bytes, object-size)",
kAllocIncrement, sizeof(T));
}
free_avail_ = kAllocIncrement;
}
result = free_area_;
free_area_ += sizeof(T);
free_avail_ -= sizeof(T);
}
inuse_++;
return reinterpret_cast<T*>(result);
}
void Delete(T* p) {
#ifndef NDEBUG
memset(static_cast<void*>(p), 0xAA, sizeof(T));
#endif
*(reinterpret_cast<void**>(p)) = free_list_;
free_list_ = p;
inuse_--;
}
int inuse() const { return inuse_; }
private:
// How much to allocate from system at a time
static const int kAllocIncrement = 128 << 10;
// Free area from which to carve new objects
char* free_area_;
size_t free_avail_;
// Free list of already carved objects
void* free_list_;
// Number of allocated but unfreed objects
int inuse_;
};
// STL-compatible allocator which forwards allocations to a PageHeapAllocator.
//
// Like PageHeapAllocator, this requires external synchronization. To avoid multiple
// separate STLPageHeapAllocator<T> from sharing the same underlying PageHeapAllocator<T>,
// the |LockingTag| template argument should be used. Template instantiations with
// different locking tags can safely be used concurrently.
template <typename T, class LockingTag>
class STLPageHeapAllocator {
public:
typedef size_t size_type;
typedef ptrdiff_t difference_type;
typedef T* pointer;
typedef const T* const_pointer;
typedef T& reference;
typedef const T& const_reference;
typedef T value_type;
template <class T1> struct rebind {
typedef STLPageHeapAllocator<T1, LockingTag> other;
};
STLPageHeapAllocator() { }
STLPageHeapAllocator(const STLPageHeapAllocator&) { }
template <class T1> STLPageHeapAllocator(const STLPageHeapAllocator<T1, LockingTag>&) { }
~STLPageHeapAllocator() { }
pointer address(reference x) const { return &x; }
const_pointer address(const_reference x) const { return &x; }
size_type max_size() const { return size_t(-1) / sizeof(T); }
void construct(pointer p, const T& val) { ::new(p) T(val); }
void construct(pointer p) { ::new(p) T(); }
void destroy(pointer p) { p->~T(); }
// There's no state, so these allocators are always equal
bool operator==(const STLPageHeapAllocator&) const { return true; }
bool operator!=(const STLPageHeapAllocator&) const { return false; }
pointer allocate(size_type n, const void* = 0) {
if (!underlying_.initialized) {
underlying_.allocator.Init();
underlying_.initialized = true;
}
CHECK_CONDITION(n == 1);
return underlying_.allocator.New();
}
void deallocate(pointer p, size_type n) {
CHECK_CONDITION(n == 1);
underlying_.allocator.Delete(p);
}
private:
struct Storage {
constexpr Storage() = default;
PageHeapAllocator<T> allocator;
bool initialized;
};
static inline Storage underlying_;
};
} // namespace tcmalloc
#endif // TCMALLOC_PAGE_HEAP_ALLOCATOR_H_