First Commit

common/ReadbackSpinManager.h

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+// SPDX-FileCopyrightText: 2002-2025 PCSX2 Dev Team
+// SPDX-License-Identifier: GPL-3.0+
+
+#pragma once
+
+#include "Pcsx2Defs.h"
+
+#include <vector>
+
+/// A class for calculating optimal spin values to trick OSes into not powering down GPUs while waiting for readbacks
+class ReadbackSpinManager
+{
+public:
+	struct Event
+	{
+		s64 size;
+		u32 begin;
+		u32 end;
+	};
+
+private:
+	double m_spins_per_unit_time = 0;
+	double m_total_spin_time = 0;
+	double m_total_spin_cycles = 0;
+	std::vector<Event> m_frames[3];
+	u32 m_current_frame = 0;
+	u32 m_reference_frame = 0;
+	u32 m_reference_frame_idx = 0;
+
+public:
+	struct DrawSubmittedReturn
+	{
+		u32 id;
+		u32 recommended_spin;
+	};
+
+	/// Call when a readback is requested
+	void ReadbackRequested();
+	/// Call at the end of a frame
+	void NextFrame();
+	/// Call when a command buffer is submitted to the GPU
+	/// `size` is used to attempt to find patterns in submissions, and can be any metric that approximates the amount of work in a submission (draw calls, command encoders, etc)
+	/// Returns an id to be passed to `DrawCompleted`, and the recommended number of spin cycles to perform on the GPU in order to keep it busy
+	DrawSubmittedReturn DrawSubmitted(u64 size);
+	/// Call once a draw has been finished by the GPU and you have begin/end data for it
+	/// `begin_time` and `end_time` can be in any unit as long as it's consistent.  It's okay if they roll over, as long as it happens less than once every few frames.
+	void DrawCompleted(u32 id, u32 begin_time, u32 end_time);
+	/// Call when a spin completes to help the manager figure out how quickly your GPU spins
+	void SpinCompleted(u32 cycles, u32 begin_time, u32 end_time);
+	/// Get the calculated number of spins per unit of time
+	/// Note: May be zero when there's insufficient data
+	double SpinsPerUnitTime() const { return m_spins_per_unit_time; }
+};