58 lines
1.6 KiB
C++
58 lines
1.6 KiB
C++
/*
|
|
* Copyright (c) Facebook, Inc. and its affiliates.
|
|
*
|
|
* 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.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <memory>
|
|
|
|
namespace folly {
|
|
namespace fibers {
|
|
|
|
class StackCacheEntry;
|
|
|
|
/**
|
|
* Stack allocator that protects an extra memory page after
|
|
* the end of the stack.
|
|
* Will only add extra memory pages up to a certain number of allocations
|
|
* to avoid creating too many memory maps for the process.
|
|
*/
|
|
class GuardPageAllocator {
|
|
public:
|
|
/**
|
|
* @param guardPagesPerStack Protect a small number of fiber stacks
|
|
* with this many guard pages. If 0, acts as std::allocator.
|
|
*/
|
|
explicit GuardPageAllocator(size_t guardPagesPerStack);
|
|
~GuardPageAllocator();
|
|
|
|
/**
|
|
* @return pointer to the bottom of the allocated stack of `size' bytes.
|
|
*/
|
|
unsigned char* allocate(size_t size);
|
|
|
|
/**
|
|
* Deallocates the previous result of an `allocate(size)' call.
|
|
*/
|
|
void deallocate(unsigned char* limit, size_t size);
|
|
|
|
private:
|
|
std::unique_ptr<StackCacheEntry> stackCache_;
|
|
std::allocator<unsigned char> fallbackAllocator_;
|
|
size_t guardPagesPerStack_{0};
|
|
};
|
|
} // namespace fibers
|
|
} // namespace folly
|