Memory Leak using .net SerialPort, is there a better way?

I have a program that is used to talk to hardware over rs232. This software is used to display a stream of data that is pushed over the rs232 from the hardware as fast as it can be. The problem I am running into is that over time the private memory assigned to the program explodes, and will very rapidly cra开发者_Go百科sh the program. If I disable the hardware from sending data for about 2 minutes, then the software can clear out the memory, but only if I pause the data stream.

I am using the DataReceived event from the SerialPort, and this appears to be where the problem is at, because it will cause a memory spike even if the DataReceived function does nothing inside it. The only thing I can come up with is that every time this event is raised it creates a new thread to run, and it is happening so fast that the computer doesn't have time to run GC while the data is coming in.

Is there a more efficient way to pull data off a SerialPort object? I only care about a string when I receive a "NewLine"?

Thanks,

John Vickers

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DataReceived is executed on a different thread. I had problems with really fast data and this event caused me problems. Because of that, I created one thread and read the data myself:

while (this.serialPort.IsOpen)
{
    int b = this.serialPort.ReadByte();
    if (b != -1)
    {
        // data is good here
    }
}

But like the others said, without any code sample, there isn't much we can help you with.

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This is very unusual but it is technically possible. SerialPort uses threadpool threads to call the DataReceived event handler. As soon as it receives one or more bytes, it grabs a TP thread to notify your app. There's a lock in the event generation code, only one thread can call your event handler at a time.

A potential failure mode here is that one of these calls, likely the first one, enters a loop in your code from which it never exits. If you haven't set up the Handshake property, the device can keep sending and triggering more TP calls, all of them blocking on that lock.

Diagnose this from the Debug + Windows + Threads window. If my guess is accurate then you should see a large number of threads listed here. One of them should be inside your DataReceived event handler, double-click it and look at the call stack to see where it is stuck. The memory you are seeing consumed is eaten by the stacks of these threads, one megabyte each.

Another possibility is that your DataReceived event handling code is very slow, possibly by calling Control.Invoke(). Slow enough to not be able to keep up with the device. You now really do need to use the Handshake property to setup flow control. Or fix whatever makes it so slow. There should also be a very large number of ErrorReceived events btw, be sure to implement it so you can see this stuff going wrong.

There's an upper limit on the number of TP threads that can be running at the same time. It is rather generous, 250 times the number of cores. That can easily consume half a gigabyte of memory on a typical dual-core machine.

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Just to revive this issue.

I'm seeing a massive memory leak when using the DataReceived event.

I am using a USB 3G modem which provides a serial modem interface. I wrote a tiny program that just opens the serial port and connects to the DataReceived event. The event handler is just an empty method.

If you yank out the dongle memory starts to leak at about 10MB per second. No exception is thrown.

Spinning up a new thread and using the synchronous Read(...) method solved the problem for me. I now get an exception when I yank out the dongle that I can handle and no memory leaks.

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I developed a state-driven serial port programming language in C# and I believe it really solves nearly all of the serial port problems that everybody encounters with.

Would you please try it with the following simple state and check memory leaks ?

state Init
  recv();
  $len = length($DATA_PACKET);
  if("$len > 0") {
    log($DATA_PACKET, Debug);
  }
end state

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