Question

I am developing a program to log data from a incoming serial communication. I have to invoke the serial box by sending a command, to recieve something. All this works fine, but i have a problem.

The program have to be run from a netbook ( approx: 1,5 gHZ, 2 gig ram ), and it can’t keep up when i ask it to save these information to a XML file.

I am only getting communication every 5 second, i am not reading the file anywhere.

I use xml.save(string filename) to save the file.

Is there another, better way, to save the information to my XML, or should i use an alternative?

If i should use an alternative, which should it be?

Edit:
Added some code:

            XmlDocument xml = new XmlDocument();
            xml.Load(logFile);

            XmlNode p = xml.GetElementsByTagName("records")[0];
            for (int i = 0; i < newDat.Length; i++)
            {
                XmlNode q = xml.CreateElement("record");

                XmlNode a = xml.CreateElement("time");
                XmlNode b = xml.CreateElement("temp");
                XmlNode c = xml.CreateElement("addr");

                a.AppendChild(xml.CreateTextNode(outDat[i, 0]));
                b.AppendChild(xml.CreateTextNode(outDat[i, 1]));
                c.AppendChild(xml.CreateTextNode(outDat[i, 2]));

                sendTime = outDat[i, 0];

                points.Add(outDat[i, 2], outDat[i, 1]);

                q.AppendChild(a);
                q.AppendChild(b);
                q.AppendChild(c);

                p.AppendChild(q);
            }

            xml.AppendChild(p);
            xml.Save(this.logFile);

This is the XML related code, running once every 5 seconds. I am reading (I get no error), adding some childs, and then saving it again. It is when I save that I get the error.

Answer 1

You may want to look at using an XMLWriter and building the XML file by hand. That would allow you to open a file and keep it open for the duration of the logging, appending one XML fragment at a time, as you read in data. The XMLReader class is optimized for forward-only writing to an XMLStream.

The above approach should be much faster when compared to using the Save method to serialize (save) a full XML document each time you read data and when you really only want to append a new fragment at the end.

EDIT

Based on the code sample you posted, it’s the Load and Save that’s causing the unnecessary performance bottleneck. Every time you’re adding a log entry you’re essentially loading the full XML document and behind the scenes parsing it into a full-blown XML tree. Then you modify the tree (by adding nodes) and then serialize it all to disk again. This is very very counter productive.

My proposed solution is really the way to go: create and open the log file only once; then use an XMLWriter to write out the XML elements one by one, each time you read new data; this way you’re not holding the full contents of the XML log in memory and you’re only appending small chunks of data at the end of a file – which should be unnoticeable in terms of overhead; at the end, simply close the root XML tag, close the XMLWriter and close the file. That’s it! This is guaranteed to not slow down your UI even if you implement it synchronously, on the UI thread.