131 lines
4.6 KiB
C++
131 lines
4.6 KiB
C++
/*
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* Copyright (C) 2017 Apple Inc. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR
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* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#pragma once
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#include "Bits.h"
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#include "DeferredTrigger.h"
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#include "FreeList.h"
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#include "Mutex.h"
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#include <climits>
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#include <mutex>
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namespace bmalloc {
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class IsoHeapImplBase;
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template<typename Config> class IsoDirectoryBase;
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template<typename Config> class IsoHeapImpl;
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class IsoPageBase {
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public:
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static constexpr size_t pageSize = 16384;
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explicit IsoPageBase(bool isShared)
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: m_isShared(isShared)
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, m_eligibilityHasBeenNoted(true)
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, m_isInUseForAllocation(false)
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{
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}
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static IsoPageBase* pageFor(void*);
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bool isShared() const { return m_isShared; }
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protected:
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BEXPORT static void* allocatePageMemory();
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bool m_isShared : 1;
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bool m_eligibilityHasBeenNoted : 1;
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bool m_isInUseForAllocation : 1;
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};
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template<typename Config>
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class IsoPage : public IsoPageBase {
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public:
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static constexpr unsigned numObjects = pageSize / Config::objectSize;
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static_assert(numObjects, "IsoHeap size should allow at least one allocation per page");
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static IsoPage* tryCreate(IsoDirectoryBase<Config>& directory, unsigned index);
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// It's expected that you will only use this with placement new and direct destruction.
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IsoPage(IsoDirectoryBase<Config>& directory, unsigned index);
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static IsoPage* pageFor(void*);
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unsigned index() const { return m_index; }
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void free(const LockHolder&, void*);
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// Called after this page is already selected for allocation.
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FreeList startAllocating(const LockHolder&);
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// Called after the allocator picks another page to replace this one.
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void stopAllocating(const LockHolder&, FreeList);
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IsoDirectoryBase<Config>& directory() { return m_directory; }
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bool isInUseForAllocation() const { return m_isInUseForAllocation; }
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template<typename Func>
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void forEachLiveObject(const LockHolder&, const Func&);
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IsoHeapImpl<Config>& heap();
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private:
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static constexpr unsigned indexOfFirstObject()
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{
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return (sizeof(IsoPage) + Config::objectSize - 1) / Config::objectSize;
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}
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// The possible states of a page are as follows. We mark these states by their corresponding
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// eligible, empty, and committed bits (respectively).
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//
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// 000 - Deallocated. It has no objects and its memory is not paged in.
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// 111 - Empty.
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// 101 - Eligible for allocation, meaning that there is at least one free object in the page.
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// 001 - Full.
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// 001 - Currently being used for allocation.
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//
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// Note that the last two states have identical representation in the directory, which is fine - in
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// both cases we are basically telling the directory that this page is off limits. But we keep track
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// of the distinction internally.
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// We manage the bitvector ourselves. This bitvector works in a special way to enable very fast
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// freeing.
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// This must have a trivial destructor.
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DeferredTrigger<IsoPageTrigger::Eligible> m_eligibilityTrigger;
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DeferredTrigger<IsoPageTrigger::Empty> m_emptyTrigger;
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uint8_t m_numNonEmptyWords { 0 };
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static_assert(bitsArrayLength(numObjects) <= UINT8_MAX);
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unsigned m_index { UINT_MAX };
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IsoDirectoryBase<Config>& m_directory;
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unsigned m_allocBits[bitsArrayLength(numObjects)];
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};
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} // namespace bmalloc
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