SPU: Implement execution wake-up delay

Utilities/Thread.cpp

@@ -2322,14 +2322,14 @@ thread_state thread_ctrl::state()
 	return static_cast<thread_state>(_this->m_sync & 3);
 }
 
-void thread_ctrl::_wait_for(u64 usec, [[maybe_unused]] bool alert /* true */)
+void thread_ctrl::wait_for(u64 usec, [[maybe_unused]] bool alert /* true */)
 {
 	auto _this = g_tls_this_thread;
 
 #ifdef __linux__
 	static thread_local struct linux_timer_handle_t
 	{
-		// Allocate timer only if needed (i.e. someone calls _wait_for with alert and short period)
+		// Allocate timer only if needed (i.e. someone calls wait_for with alert and short period)
 		const int m_timer = timerfd_create(CLOCK_MONOTONIC, 0);
 
 		linux_timer_handle_t() noexcept
@@ -2383,6 +2383,58 @@ void thread_ctrl::_wait_for(u64 usec, [[maybe_unused]] bool alert /* true */)
 	list.wait(atomic_wait_timeout{usec <= 0xffff'ffff'ffff'ffff / 1000 ? usec * 1000 : 0xffff'ffff'ffff'ffff});
 }
 
+void thread_ctrl::wait_for_accurate(u64 usec)
+{
+	if (!usec)
+	{
+		return;
+	}
+
+	using namespace std::chrono_literals;
+
+	const auto until = std::chrono::steady_clock::now() + 1us * usec;
+
+	while (true)
+	{
+#ifdef __linux__
+		// NOTE: Assumption that timer initialization has succeeded
+		u64 host_min_quantum = usec <= 1000 ? 10 : 50;
+#else
+		// Host scheduler quantum for windows (worst case)
+		// NOTE: On ps3 this function has very high accuracy
+		constexpr u64 host_min_quantum = 500;
+#endif
+		if (usec >= host_min_quantum)
+		{
+#ifdef __linux__
+			// Do not wait for the last quantum to avoid loss of accuracy
+			wait_for(usec - ((usec % host_min_quantum) + host_min_quantum), false);
+#else
+			// Wait on multiple of min quantum for large durations to avoid overloading low thread cpus
+			wait_for(usec - (usec % host_min_quantum), false);
+#endif
+		}
+		// TODO: Determine best value for yield delay
+		else if (usec >= host_min_quantum / 2)
+		{
+			std::this_thread::yield();
+		}
+		else
+		{
+			busy_wait(100);
+		}
+
+		const auto current = std::chrono::steady_clock::now();
+
+		if (current >= until)
+		{
+			break;
+		}
+
+		usec = (until - current).count();
+	}
+}
+
 std::string thread_ctrl::get_name_cached()
 {
 	auto _this = thread_ctrl::g_tls_this_thread;