[WIP] Low-latency cycle control

2 files changed, 22 insertions, 33 deletions

diff --git a/src/cpu/cpu.cpp b/src/cpu/cpu.cpp
index ab1240393..334ccb868 100644
--- a/src/cpu/cpu.cpp
+++ b/src/cpu/cpu.cpp
@@ -2128,10 +2128,7 @@ static void CPU_CycleIncrease(bool pressed) {
 	    
 		CPU_CycleLeft=0;CPU_Cycles=0;
 		if (CPU_CycleMax==old_cycles) CPU_CycleMax++;
-		if(CPU_CycleMax > 15000 ) 
-			LOG_MSG("CPU speed: fixed %d cycles. If you need more than 20000, try core=dynamic in DOSBox's options.",CPU_CycleMax);
-		else
-			LOG_MSG("CPU speed: fixed %d cycles.",CPU_CycleMax);
+		LOG_MSG("CPU speed: fixed %d cycles.",CPU_CycleMax);
 		GFX_SetTitle(CPU_CycleMax,-1,false);
 	}
 }
diff --git a/src/dosbox.cpp b/src/dosbox.cpp
index 688609a71..de0ee3cb1 100644
--- a/src/dosbox.cpp
+++ b/src/dosbox.cpp
@@ -160,6 +160,9 @@ bool mono_cga=false;
 void increaseticks_fixed();
 
 static constexpr auto frame_pace_us = usT(1000 * 1000 / 60);
+static constexpr uint32_t frame_pace_ms = frame_pace_us.count() / 1000;
+static int32_t target_cycles;
+
 static int frame_balance = 0;
 static int pic_balance = 0;
 static std::thread pic_pacer;
@@ -223,39 +226,27 @@ static Bitu Normal_Loop()
 void increaseticks_fixed()
 {
 	const auto ticksNew = GetTicks();
-	if (ticksNew <= ticksLast) {
-
-		while (pic_balance < 1)
-			std::this_thread::sleep_for(usT(50));
-		std::lock_guard<std::mutex> guard(pic_balance_mutex);
-		pic_balance = 0;
+	if (ticksNew > ticksLast) {
+		ticksRemain = ticksNew - ticksLast;
+		ticksLast = ticksNew;
+
+		if (ticksRemain > frame_pace_ms) {
+			CPU_CycleMax -= CPU_CycleMax / 10;
+			ticksRemain = frame_pace_ms;
+			LOG_MSG("Dropped cycles to %u", CPU_CycleMax);
+		}
+		else if (ticksRemain > 3 && CPU_CycleMax < target_cycles) {
+			CPU_CycleMax += CPU_CycleMax / 25;
+			LOG_MSG("Bumped cycles to %u", CPU_CycleMax);
+		}
 		return;
 	}
-
-	constexpr long int max_ticks_remaing = 20;
-	ticksRemain = std::min(max_ticks_remaing, ticksNew - ticksLast);
-	ticksLast = ticksNew;
-	/* 	if (ticksRemain > 20)
-	                ticksRemain = 20; */
+	while (pic_balance < 1)
+		std::this_thread::sleep_for(usT(50));
+	std::lock_guard<std::mutex> guard(pic_balance_mutex);
+	pic_balance = 0;
 }
 
-/* uint32_t t_remain = 0;
-uint32_t t_last = 0;
-
-void increaseticks_fixed()
-{
-        const uint32_t t_new = GetTicks();
-        if (t_new <= t_last) {
-                while (pic_balance < 1)
-                        std::this_thread::sleep_for(usT(50));
-                std::lock_guard<std::mutex> guard(pic_balance_mutex);
-                pic_balance = 0;
-                return;
-        }
-        t_remain = std::min(20u, t_new - t_last);
-        t_last = t_new;
-} */
-
 // For trying other delays
 #define wrap_delay(a) SDL_Delay(a)
 
@@ -406,6 +397,7 @@ void DOSBOX_RunMachine()
 		pic_pacer.detach();
 		frame_pacer = std::thread(&pace_frame);
 		frame_pacer.detach();
+		target_cycles = CPU_CycleMax;
 		started = true;
 	}