/* * Copyright (C) 2017 Apple 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: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. 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. * * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``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 APPLE INC. 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. */ #pragma once #include "Bits.h" #include "DeferredTrigger.h" #include "FreeList.h" #include <climits> namespace bmalloc { template<typename Config> class IsoDirectoryBase; template<typename Config> class IsoHeapImpl; class IsoPageBase { public: static constexpr size_t pageSize = 16384; protected: BEXPORT static void* allocatePageMemory(); }; template<typename Config> class IsoPage : public IsoPageBase { public: static constexpr unsigned numObjects = pageSize / Config::objectSize; static_assert(numObjects, "IsoHeap size should allow at least one allocation per page"); static IsoPage* tryCreate(IsoDirectoryBase<Config>& directory, unsigned index); // It's expected that you will only use this with placement new and direct destruction. IsoPage(IsoDirectoryBase<Config>& directory, unsigned index); static IsoPage* pageFor(void*); unsigned index() const { return m_index; } void free(void*); // Called after this page is already selected for allocation. FreeList startAllocating(); // Called after the allocator picks another page to replace this one. void stopAllocating(FreeList freeList); IsoDirectoryBase<Config>& directory() { return m_directory; } bool isInUseForAllocation() const { return m_isInUseForAllocation; } template<typename Func> void forEachLiveObject(const Func&); IsoHeapImpl<Config>& heap(); private: static constexpr unsigned indexOfFirstObject() { return (sizeof(IsoPage) + Config::objectSize - 1) / Config::objectSize; } IsoDirectoryBase<Config>& m_directory; unsigned m_index { UINT_MAX }; // The possible states of a page are as follows. We mark these states by their corresponding // eligible, empty, and committed bits (respectively). // // 000 - Deallocated. It has no objects and its memory is not paged in. // 111 - Empty. // 101 - Eligible for allocation, meaning that there is at least one free object in the page. // 001 - Full. // 001 - Currently being used for allocation. // // Note that the last two states have identical representation in the directory, which is fine - in // both cases we are basically telling the directory that this page is off limits. But we keep track // of the distinction internally. // We manage the bitvector ourselves. This bitvector works in a special way to enable very fast // freeing. // This must have a trivial destructor. unsigned m_allocBits[bitsArrayLength(numObjects)]; unsigned m_numNonEmptyWords { 0 }; bool m_eligibilityHasBeenNoted { true }; bool m_isInUseForAllocation { false }; DeferredTrigger<IsoPageTrigger::Eligible> m_eligibilityTrigger; DeferredTrigger<IsoPageTrigger::Empty> m_emptyTrigger; }; } // namespace bmalloc