Tons of stuttering in XNA?

Question

As stated in the title, my program stutters like crazy, even though my program for the most part runs for 60 fps. During the moments it stutters, FPS momentarily drops down to 59(stats from FRAPS).

Here is an video capture of the stuttering in action. If you look closely, you can see the game stutter around 3-4 times. It is much more noticeable in real life.

http://gfycat.com/SevereCanineBabirusa

CLR Profiler shows that garbage collection doesn't run at all during that time, never mind 4 times, so it's not that.

Here's the code for movement:

            //Movement logic
            //Increase the speed
            speed = Math.Min(speed + (speedIncrement * (gameTime.ElapsedGameTime.Milliseconds / 200.0f)), maxSpeed);

            for (int i = fruits.Count - 1; i >= 0; i--)
            {
                //Move the fruits
                fruits[i].pos.Y += speed * gameTime.ElapsedGameTime.Milliseconds;
                fruits[i].rect.Y = (int)fruits[i].pos.Y;
                //Check if the fruit is past the screen. If it is, remove it from fruits
                if (fruits[i].rect.Y > screenHeight)
                {
                    fruits.Remove(fruits[i]);
                }
            }

IsFixedTimeStep is set to false, but SyncronizeWithVerticalTrace is on. Any idea what could be the cause of the stuttering?

EDIT: Apparently it was a combination of this: http://answers.microsoft.com/en-us/windows/forum/windows_7-performance/presentationfontcacheexe-uses-50-of-my-cpu/4200fe85-458f-4f19-b791-1fe5395304da and f.lux eating up my CPU/GPU cycles.

Answer 1

Try using Stopwatch to capture a start and end time at the beginning and end of your Update method to find an average time spent in Update. Then, add a branch to a breakpoint when the time exceeds the average by some threshold and take a look at the program state at that time.

You might consider recycling your objects by moving them to a pool, instead of simply forgetting about them altogether. While it probably isn't the GC interrupting the flow, it worth checking out.

Also, try building the game in Release mode instead of Debug, if you haven't done so already.

Answer 2

Set IsFixedTimestep = false. But in doing so, you'll need to consider Shawn Hargreaves' explanation first: http://xboxforums.create.msdn.com/forums/p/9934/53561.aspx#53561.