// 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 NULL, size_t
#include "common.h" // for MetaDataAlloc
#include "free_list.h" // for FL_Push/FL_Pop
#include "internal_logging.h" // for ASSERT
#include "system-alloc.h" // for TCMalloc_SystemAddGuard
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:
// 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_ = NULL;
free_avail_ = 0;
free_list_ = NULL;
// Reserve some space at the beginning to avoid fragmentation.
Delete(New());
}
T* New() {
// Consult free list
void* result;
if (free_list_ != NULL) {
result = FL_Pop(&free_list_);
} 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_ == NULL) {
Log(kCrash, __FILE__, __LINE__,
"FATAL ERROR: Out of memory trying to allocate internal "
"tcmalloc data (bytes, object-size)",
kAllocIncrement, sizeof(T));
}
// This guard page protects the metadata from being corrupted by a
// buffer overrun. We currently have no mechanism for freeing it, since
// we never release the metadata buffer. If that changes we'll need to
// add something like TCMalloc_SystemRemoveGuard.
size_t guard_size = TCMalloc_SystemAddGuard(free_area_,
kAllocIncrement);
free_area_ += guard_size;
free_avail_ = kAllocIncrement - guard_size;
if (free_avail_ < sizeof(T)) {
Log(kCrash, __FILE__, __LINE__,
"FATAL ERROR: Insufficient memory to guard internal tcmalloc "
"data (%d bytes, object-size %d, guard-size %d)\n",
kAllocIncrement, static_cast<int>(sizeof(T)), guard_size);
}
}
result = free_area_;
free_area_ += sizeof(T);
free_avail_ -= sizeof(T);
}
inuse_++;
return reinterpret_cast<T*>(result);
}
void Delete(T* p) {
FL_Push(&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_;
};
} // namespace tcmalloc
#endif // TCMALLOC_PAGE_HEAP_ALLOCATOR_H_