XElement - LoadOptions.SetLineInfo - very slow & memory times 2

[304NotModified]

Hi,

I noticed that using XElement.Load(stream, LoadOptions.SetLineInfo) is very slow and memory consuming is times 2 compared to XElement.Load(stream, LoadOptions.None)

See table. For the completeness, I also added the results for the generated for class (XSD to C#) - which is very fast and not using much memory but is lacking the lineinfo.

Tested it with a XML file of 914MB

Method	Memory	Time
XElement without lineinfo (LoadOptions.None)	2.213.541 Mb (2.271.092.736 bytes)	27 Sec (26.502 ms)
XElement with lineinfo (LoadOptions.SetLineInfo)	5.523.492 Mb (5.667.102.720 bytes)	46 Sec (45.781 ms)
Own "XElement" without lineinfo	2.825.026 Mb (2.898.477.056 bytes)	25 Sec (24.584 ms)
Own "XElement" with lineinfo	2.825.226 Mb (2.898.681.856 bytes)	26 Sec (25.969 ms)
XSD generated classes	845.057 Mb (867.028.992 bytes)	27 Sec (26.966 ms)

Own "XElement"

The funny part is that I wrote my own "XElement" in the past, and there is nearly no difference in capturing the lineInfo compared to non-capure. I'm doing for all element and all attributes XmlPosition.Create(reader):

public struct XmlPosition
{
    public XmlPosition(int lineNumber, int columnNumber)
    {
        if (lineNumber < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(lineNumber));
        }

        if (columnNumber < 0)
        {
            throw new ArgumentOutOfRangeException(nameof(columnNumber));
        }

        LineNumber = lineNumber;
        ColumnNumber = columnNumber;
    }
    
    public int LineNumber { get; }

    public int ColumnNumber { get;  }

    public static XmlPosition Create(System.Xml.XmlReader reader)
    {
        if(reader is IXmlLineInfo lineInfo)
        {
            return new XmlPosition(lineInfo.LineNumber, lineInfo.LinePosition);
        }
        
        throw new NotImplementedException("ow noos");
    }
}

So I can't understand why the XElement is using so much memory/time for SetLineInfo!

XmlReaderSettings

PS: also tried, but no significant change.

var options = new XmlReaderSettings();
options.IgnoreWhitespace = true;
options.DtdProcessing = DtdProcessing.Ignore;
options.MaxCharactersFromEntities = 10000000L;
options.Async = true;
options.CloseInput = true;


XElement xml;
using (XmlReader reader = XmlReader.Create(s, options))
{
    xml = XElement.Load(reader, LoadOptions.SetLineInfo);
}

Test

• using Process.GetCurrentProcess().WorkingSet64 for memory
• using System.Diagnostics.StopWatch for timings

Env

Tested with .NET Core 2.2, Windows Server 2016 datacenter

[krwq]

@304NotModified this is something we would have to investigate. Do you have your xml file somewhere permanently available? Do you perhaps have perf logs with and without line info available to compare?

Would you be interested in doing the investigation/fixes?

PS. We have merged corefx and coreclr into dotnet/runtime repo so that's where the issue should be filed (it will get moved there eventually)

[danmoseley]

@304NotModified as an aside, we recommend using Benchmark.NET for profiling. This is what we use ourselves. Although, in this case the difference seems to be large enough that it doesn't matter...