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107 lines
3.4 KiB
C++
107 lines
3.4 KiB
C++
/*============================================================================*/
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/*
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VFLib: https://github.com/vinniefalco/VFLib
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Copyright (C) 2008 by Vinnie Falco <vinnie.falco@gmail.com>
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This library contains portions of other open source products covered by
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separate licenses. Please see the corresponding source files for specific
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terms.
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VFLib is provided under the terms of The MIT License (MIT):
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Permission is hereby granted, free of charge, to any person obtaining a copy
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of this software and associated documentation files (the "Software"), to deal
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in the Software without restriction, including without limitation the rights
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to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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copies of the Software, and to permit persons to whom the Software is
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furnished to do so, subject to the following conditions:
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The above copyright notice and this permission notice shall be included in
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all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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IN THE SOFTWARE.
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*/
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/*============================================================================*/
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#ifndef BEAST_PAGEDFREESTORE_BEASTHEADER
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#define BEAST_PAGEDFREESTORE_BEASTHEADER
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/*============================================================================*/
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/**
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Lock-free memory allocator for fixed size pages.
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The ABA problem (http://en.wikipedia.org/wiki/ABA_problem) is avoided by
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treating freed pages as garbage, and performing a collection every second.
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@ingroup beast_concurrent
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*/
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class PagedFreeStore : private OncePerSecond
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{
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public:
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explicit PagedFreeStore (const size_t pageBytes);
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~PagedFreeStore ();
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// The available bytes per page is a little bit less
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// than requested in the constructor, due to overhead.
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//
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inline size_t getPageBytes () const
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{
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return m_pageBytesAvailable;
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}
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inline void* allocate (const size_t bytes)
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{
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if (bytes > m_pageBytes)
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Throw (Error ().fail (__FILE__, __LINE__, "the size is too large"));
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return allocate ();
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}
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void* allocate ();
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static void deallocate (void* const p);
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private:
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void* newPage ();
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void doOncePerSecond ();
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private:
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struct Page;
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typedef LockFreeStack <Page> Pages;
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struct Pool
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{
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CacheLine::Padded <Pages> fresh;
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CacheLine::Padded <Pages> garbage;
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};
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static inline void* fromPage (Page* const p);
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static inline Page* toPage (void* const p);
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void dispose (Pages& pages);
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void dispose (Pool& pool);
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private:
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const size_t m_pageBytes;
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const size_t m_pageBytesAvailable;
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CacheLine::Aligned <Pool> m_pool1; // pair of pools
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CacheLine::Aligned <Pool> m_pool2;
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Pool* volatile m_cold; // pool which is cooling down
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Pool* volatile m_hot; // pool we are currently using
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AtomicCounter m_newPagesLeft; // limit of system allocations
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#if 1
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int m_swaps;
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AtomicCounter m_total;
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AtomicCounter m_used;
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#endif
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};
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#endif
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