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https://github.com/FEX-Emu/FEX.git
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Ryan Houdek
d2c92808f5
NFC - Renames CodeBufferManager to SharedCodeBufferManager to be more explicit about it being shared between threads - Renames `CodeBuffers` to `SharedCodeBuffers` to make it more explicit about sharing these buffers between threads. - Separates the Manager to its own file so it is distinct from the rest of the CPUBackend code Makes it easier to parse ownership and lifetime semantics of these buffers.
74 lines
2.6 KiB
C++
74 lines
2.6 KiB
C++
// SPDX-License-Identifier: MIT
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/*
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$info$
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category: Thread shared code buffer management
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tags: backend|shared
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$end_info$
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*/
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#pragma once
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#include <FEXCore/fextl/memory.h>
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#include <FEXCore/Utils/SignalScopeGuards.h>
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namespace FEXCore {
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struct GuestToHostMap;
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}
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namespace FEXCore::CPU {
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struct CodeBuffer {
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uint8_t* Ptr;
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size_t AllocatedSize; // including guard page; see UsableSize()
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fextl::unique_ptr<GuestToHostMap> LookupCache;
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CodeBuffer(size_t Size);
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CodeBuffer(const CodeBuffer&) = delete;
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CodeBuffer& operator=(const CodeBuffer&) = delete;
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CodeBuffer(CodeBuffer&& oth) = delete;
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CodeBuffer& operator=(CodeBuffer&&) = delete;
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~CodeBuffer();
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/// Returns the number of bytes available for storing code
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size_t UsableSize() const {
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return AllocatedSize - FEXCore::Utils::FEX_PAGE_SIZE;
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}
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};
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/**
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* A manager that coordinates access to the CodeBuffer used for compiling new code across threads.
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*
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* The CodeBuffer is managed as a partially persistent data structure:
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* - Exactly one CodeBuffer is now designated as "active", which means data can be appended to it
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* - Lossy modifications to the active CodeBuffer will not invalidate any data in use by other threads (which is what enables save CodeBuffer sharing across threads)
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* - Instead, such lossy modifications trigger a new "version" of the data in the modifying thread. Old versions of the CodeBuffer persist as read-only data for use by the other threads.
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* - The other threads can update their version of the CodeBuffer. This will decrease the reference count and eventually trigger deallocation of the old version
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*/
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class SharedCodeBufferManager {
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public:
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// Get the CodeBuffer that was most recently allocated.
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// This is the only CodeBuffer that data may be written to.
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fextl::shared_ptr<CodeBuffer> GetLatest();
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// Allocate a new CodeBuffer with geometric growth up to an internal maximum.
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// Subsequent calls to GetLatest will point to the returned buffer.
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fextl::shared_ptr<CodeBuffer> StartLargerCodeBuffer();
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// Allocate a new CodeBuffer with maximum internal size.
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// Subsequent calls to GetLatest will point to the returned buffer.
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fextl::shared_ptr<CodeBuffer> StartMaximalCodeBuffer();
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// Write offset into the latest CodeBuffer
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std::size_t LatestOffset {};
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// Protects writes to the latest CodeBuffer and changes to LatestOffset
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FEXCore::ForkableUniqueMutex CodeBufferWriteMutex;
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virtual void OnCodeBufferAllocated(const std::shared_ptr<CodeBuffer>&) {};
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private:
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fextl::shared_ptr<CodeBuffer> Latest;
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fextl::shared_ptr<CodeBuffer> AllocateNew(size_t Size);
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};
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} // namespace FEXCore::CPU
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