Add Yield/SwitchToThread in SNES IPCRingBuffer. Improves performance on Core 2 Duo, about the same on i5, and will prevent it from going < 1 fps on a single core machine :).

BizHawk.Common/IPC/IPCRingBuffer.cs

@@ -4,13 +4,14 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
 using System.IO.MemoryMappedFiles;
+using System.Threading;
 
 
 namespace BizHawk.Common
 {
 	/// <summary>
 	/// a ring buffer suitable for IPC. It uses a spinlock to control access, so overhead can be kept to a minimum. 
-	/// you'll probably need to use this in pairs, so it will occupy two threads and degrade entirely if there is less than one processor.
+	/// you'll probably need to use this in pairs, so it will occupy two threads.
 	/// </summary>
 	public unsafe class IPCRingBuffer : IDisposable
 	{
@@ -80,6 +81,7 @@ namespace BizHawk.Common
 				if (Available > amt)
 					return;
 				//this is a greedy spinlock.
+				Thread.Yield();
 			}
 		}
 
@@ -119,6 +121,7 @@ namespace BizHawk.Common
 				if (available > 0)
 					return available;
 				//this is a greedy spinlock.
+				Thread.Yield();
 			}
 		}
 

libsnes/bsnes/target-libsnes/libsnes_pwrap.cpp

@@ -231,6 +231,7 @@ private:
 			if (Available() > amt)
 				return;
 			//this is a greedy spinlock.
+			SwitchToThread();
 		}
 	}
 
@@ -284,6 +285,7 @@ public:
 			if (available > 0)
 				return available;
 			//this is a greedy spinlock.
+			SwitchToThread();
 			//NOTE: it's annoying right now because libsnes processes die and eat a whole core.
 			//we need to gracefully exit somehow
 		}
@@ -504,71 +506,71 @@ Blob ReadPipeBlob()
 	return ret;
 }
 
-void snes_video_refresh(const uint32_t *data, unsigned width, unsigned height)
-{
+void snes_video_refresh(const uint32_t *data, unsigned width, unsigned height)
+{
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
 	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_video_refresh;
 	s_EmulationControl.cb_video_refresh_params.data = data;
 	s_EmulationControl.cb_video_refresh_params.width = width;
 	s_EmulationControl.cb_video_refresh_params.height = height;
 
-	SETCONTROL;
-}
-
-bool audio_en = false;
-static const int AUDIOBUFFER_SIZE = 44100*2;
-uint16_t audiobuffer[AUDIOBUFFER_SIZE];
-int audiobuffer_idx = 0;
-
-void SIG_FlushAudio()
-{
+	SETCONTROL;
+}
+
+bool audio_en = false;
+static const int AUDIOBUFFER_SIZE = 44100*2;
+uint16_t audiobuffer[AUDIOBUFFER_SIZE];
+int audiobuffer_idx = 0;
+
+void SIG_FlushAudio()
+{
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
 	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_audio_flush;
 	SETCONTROL;
-}
-
-//this is the raw callback from the emulator internals when a new audio sample is available
-void snes_audio_sample(uint16_t left, uint16_t right)
-{
-	if(!audio_en) return;
-
-	//if theres no room in the audio buffer, we need to send a flush signal
-	if(audiobuffer_idx == AUDIOBUFFER_SIZE)
-		SIG_FlushAudio();
-
-	audiobuffer[audiobuffer_idx++] = left;
+}
+
+//this is the raw callback from the emulator internals when a new audio sample is available
+void snes_audio_sample(uint16_t left, uint16_t right)
+{
+	if(!audio_en) return;
+
+	//if theres no room in the audio buffer, we need to send a flush signal
+	if(audiobuffer_idx == AUDIOBUFFER_SIZE)
+		SIG_FlushAudio();
+
+	audiobuffer[audiobuffer_idx++] = left;
 	audiobuffer[audiobuffer_idx++] = right;
-}
-
-void snes_input_poll(void)
-{
+}
+
+void snes_input_poll(void)
+{
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
-	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_poll;
-	SETCONTROL;
-}
-int16_t snes_input_state(unsigned port, unsigned device, unsigned index, unsigned id)
-{
+	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_poll;
+	SETCONTROL;
+}
+int16_t snes_input_state(unsigned port, unsigned device, unsigned index, unsigned id)
+{
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
-	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_state;
-	s_EmulationControl.cb_input_state_params.port = port;
-	s_EmulationControl.cb_input_state_params.device = device;
-	s_EmulationControl.cb_input_state_params.index = index;
-	s_EmulationControl.cb_input_state_params.id = id;
-	SETCONTROL;
-	return s_EmulationControl.cb_input_state_params.result;
-}
-void snes_input_notify(int index)
-{
+	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_state;
+	s_EmulationControl.cb_input_state_params.port = port;
+	s_EmulationControl.cb_input_state_params.device = device;
+	s_EmulationControl.cb_input_state_params.index = index;
+	s_EmulationControl.cb_input_state_params.id = id;
+	SETCONTROL;
+	return s_EmulationControl.cb_input_state_params.result;
+}
+void snes_input_notify(int index)
+{
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
-	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_notify;
-	s_EmulationControl.cb_input_notify_params.index = index;
-	SETCONTROL;
-}
-
+	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_input_notify;
+	s_EmulationControl.cb_input_notify_params.index = index;
+	SETCONTROL;
+}
+
 void snes_trace(const char *msg)
 {
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
-	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_trace;
+	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_trace;
 	s_EmulationControl.cb_trace_params.msg = msg;
 	SETCONTROL;
 }
@@ -606,24 +608,24 @@ public:
 
 static std::map<void*,SharedMemoryBlock*> memHandleTable;
 
-void* implementation_snes_allocSharedMemory()
-{
-	const char* memtype = s_EmulationControl.cb_allocSharedMemory_params.memtype;
-	size_t amt = s_EmulationControl.cb_allocSharedMemory_params.amt;
-
-	if(!running)
-	{
-		s_EmulationControl.cb_allocSharedMemory_params.result = NULL;
-		return NULL;
-	}
-
-	//printf("WritePipe(eMessage_SIG_allocSharedMemory)\n");
-	WritePipe(eMessage_SIG_allocSharedMemory);
-	WritePipeString(memtype);
-	WritePipe(amt);
-	
-	std::string blockname = ReadPipeString();
-
+void* implementation_snes_allocSharedMemory()
+{
+	const char* memtype = s_EmulationControl.cb_allocSharedMemory_params.memtype;
+	size_t amt = s_EmulationControl.cb_allocSharedMemory_params.amt;
+
+	if(!running)
+	{
+		s_EmulationControl.cb_allocSharedMemory_params.result = NULL;
+		return NULL;
+	}
+
+	//printf("WritePipe(eMessage_SIG_allocSharedMemory)\n");
+	WritePipe(eMessage_SIG_allocSharedMemory);
+	WritePipeString(memtype);
+	WritePipe(amt);
+	
+	std::string blockname = ReadPipeString();
+
 	auto mapfile = OpenFileMapping(FILE_MAP_READ | FILE_MAP_WRITE, FALSE, blockname.c_str());
 	
 	if(mapfile == INVALID_HANDLE_VALUE)
@@ -636,36 +638,36 @@ void* implementation_snes_allocSharedMemory()
 	smb->handle = mapfile;
 
 	memHandleTable[ptr] = smb;
-	
-	s_EmulationControl.cb_allocSharedMemory_params.result = ptr;
+	
+	s_EmulationControl.cb_allocSharedMemory_params.result = ptr;
 }
 
-void* snes_allocSharedMemory(const char* memtype, size_t amt)
-{
-	//its important that this happen before the message marshaling because allocation/free attempts can happen before the marshaling is setup (or at shutdown time, in case of errors?)
-	if(!running) return NULL;
-
+void* snes_allocSharedMemory(const char* memtype, size_t amt)
+{
+	//its important that this happen before the message marshaling because allocation/free attempts can happen before the marshaling is setup (or at shutdown time, in case of errors?)
+	if(!running) return NULL;
+
 	s_EmulationControl.exitReason = eEmulationExitReason_SIG;
 	s_EmulationControl.exitCallbackType = eEmulationCallback_snes_allocSharedMemory;
 	s_EmulationControl.cb_allocSharedMemory_params.memtype = memtype;
 	s_EmulationControl.cb_allocSharedMemory_params.amt = amt;
 	SETCONTROL;
-	
-	return s_EmulationControl.cb_allocSharedMemory_params.result;
-}
-
-void implementation_snes_freeSharedMemory()
-{
-	void* ptr = s_EmulationControl.cb_freeSharedMemory_params.ptr;
+	
+	return s_EmulationControl.cb_allocSharedMemory_params.result;
+}
+
+void implementation_snes_freeSharedMemory()
+{
+	void* ptr = s_EmulationControl.cb_freeSharedMemory_params.ptr;
 	if(!ptr) return;
 	auto smb = memHandleTable.find(ptr)->second;
 	UnmapViewOfFile(ptr);
 	CloseHandle(smb->handle);
 	//printf("WritePipe(eMessage_SIG_freeSharedMemory);\n");
-	WritePipe(eMessage_SIG_freeSharedMemory);
-	WritePipeString(smb->memtype.c_str());
-}
-
+	WritePipe(eMessage_SIG_freeSharedMemory);
+	WritePipeString(smb->memtype.c_str());
+}
+
 void snes_freeSharedMemory(void* ptr)
 {
 	//its important that this happen before the message marshaling because allocation/free attempts can happen before the marshaling is setup (or at shutdown time, in case of errors?)
@@ -997,7 +999,7 @@ TOP:
 					break;
 				}
 			case eEmulationCallback_snes_audio_flush:
-				Handle_SIG_audio_flush();
+				Handle_SIG_audio_flush();
 				break;
 			case eEmulationCallback_snes_input_poll:
 				WritePipe(eMessage_SIG_input_poll);
@@ -1203,13 +1205,13 @@ void emuthread()
 			//EDIT - well, we changed that, but.. we still want this probably, for debugging and stuff
 			for(;;)
 			{
-				SNES::scheduler.sync = SNES::Scheduler::SynchronizeMode::None;
-				SNES::scheduler.clearExitReason();
-				SNES::scheduler.enter();
-				if(SNES::scheduler.exit_reason() == SNES::Scheduler::ExitReason::FrameEvent)
-				{
-					SNES::video.update();
-					break;
+				SNES::scheduler.sync = SNES::Scheduler::SynchronizeMode::None;
+				SNES::scheduler.clearExitReason();
+				SNES::scheduler.enter();
+				if(SNES::scheduler.exit_reason() == SNES::Scheduler::ExitReason::FrameEvent)
+				{
+					SNES::video.update();
+					break;
 				}
 				//not used yet
 				if(SNES::scheduler.exit_reason() == SNES::Scheduler::ExitReason::DebuggerEvent)
@@ -1273,7 +1275,7 @@ int xmain(int argc, char** argv)
 	printf("running\n");
 
 	RunControlMessageLoop();
-	
+	
 	return 0;
 }