Measure game code performance in engine

engine/engine.c

@@ -13,6 +13,14 @@
 #define FRAMERATE 60
 #define INTERVAL (1000 / FRAMERATE)
 
+#define VT100_CURSORTOPLEFT "\33[H"
+#define VT100_CLEAR "\33[2J"
+
+typedef struct {
+	double freq;
+	uint64_t start, evt, update, render;
+} perf_t;
+
 int main(int argc, char *argv[])
 {
 	int err = SDL_Init(SDL_INIT_VIDEO);
@@ -29,33 +37,54 @@ int main(int argc, char *argv[])
 	void *gamemem = calloc(1, game_conf.memsize);
 	game_init(argc, argv, gamemem, renderer);
 
-	uint64_t prevt = SDL_GetTicks64();
+	perf_t perf = { .freq = SDL_GetPerformanceFrequency() / 1000000.0 };
+	uint64_t frame = 0, prevt = SDL_GetTicks64();
 	while (1) {
-		uint64_t t = SDL_GetTicks64();
-		uint64_t dt = t - prevt;
-
+		const uint64_t t = SDL_GetTicks64();
+		const uint64_t dt = t - prevt;
 		if (dt >= INTERVAL) {
+			perf.start = SDL_GetPerformanceCounter();
+
 			// Handle all events currently in queue
 			SDL_Event evt;
 			while (SDL_PollEvent(&evt)) {
 				if (game_evthandle(gamemem, &evt) != GAMESTATUS_OK)
 					goto quit;
 			}
+			perf.evt = SDL_GetPerformanceCounter();
 
 			// Update game state
-			if (game_update(gamemem, dt) != GAMESTATUS_OK)
+			if (game_update(gamemem, INTERVAL) != GAMESTATUS_OK)
 				goto quit;
+			perf.update = SDL_GetPerformanceCounter();
 
 			// Render frame
 			SDL_RenderClear(renderer);
 			game_render(gamemem, renderer, t);
 			SDL_RenderPresent(renderer);
+			perf.render = SDL_GetPerformanceCounter();
 
-			// Set previous frame draw time
+			// Print performance if frame counter divisible by 8
+			if ((frame & 7) == 0) {
+				const double evt = (perf.evt - perf.start) / perf.freq;
+				const double update = (perf.update - perf.evt) / perf.freq;
+				const double render
+				    = (perf.render - perf.update) / perf.freq;
+				const double total = (perf.render - perf.start) / perf.freq;
+				const double total_pc = (100 * total / (1000 * INTERVAL));
+				printf(
+					VT100_CLEAR VT100_CURSORTOPLEFT
+				    "evt\t%10.3f μs\nupdate\t%10.3f μs\nrender\t"
+				    "%10.3f μs\ntotal\t%10.3f μs (%05.2f%%)\n",
+				    evt, update, render, total, total_pc);
+			}
+
+			// Increment frame counter and update time
+			++frame;
 			prevt = t;
 		}
 
-		SDL_Delay(2);
+		SDL_Delay(INTERVAL / 8);
 	}
 
 quit: