UriHelper.GetDisplayUrl: opportunity for performance improvement

[paulomorgado]

Notes:

• May 8th, 2024
  Updated to .NET 8.0

Summary

UriHelper.GetDisplayUrl uses a non-pooled StringBuilder that is instantiated on every invocation. Although optimized in size, it is a heap allocation with an intermediary buffer.

public static string GetDisplayUrl(this HttpRequest request)
{
    var scheme = request.Scheme ?? string.Empty;
    var host = request.Host.Value ?? string.Empty;
    var pathBase = request.PathBase.Value ?? string.Empty;
    var path = request.Path.Value ?? string.Empty;
    var queryString = request.QueryString.Value ?? string.Empty;

    // PERF: Calculate string length to allocate correct buffer size for StringBuilder.
    var length = scheme.Length + SchemeDelimiter.Length + host.Length
        + pathBase.Length + path.Length + queryString.Length;

    return new StringBuilder(length)
        .Append(scheme)
        .Append(SchemeDelimiter)
        .Append(host)
        .Append(pathBase)
        .Append(path)
        .Append(queryString)
        .ToString();
}

Motivation and goals

This method is frequently used in hot paths like redirect and rewrite rules.

From the benchmarks below, we can see that, compared to the current implementation using a StringBuilder with enough capacity, string interpolation is around 3 times better in terms of duration and around 4 times in memory used.

String.Create is even more performant.

Benchmarks

BenchmarkDotNet v0.13.12, Windows 11 (10.0.22631.3527/23H2/2023Update/SunValley3)
13th Gen Intel Core i9-13900K, 1 CPU, 32 logical and 24 physical cores
.NET SDK 8.0.300-preview.24203.14
  [Host]     : .NET 8.0.4 (8.0.424.16909), X64 RyuJIT AVX2
  DefaultJob : .NET 8.0.4 (8.0.424.16909), X64 RyuJIT AVX2

Method	scheme	host	basePath	path	query	Mean	Ratio	Gen0	Allocated	Alloc Ratio
StringBuilder	http	cname.domain.tld		/		69.988 ns	1.00	0.0288	544 B	1.00
String_Interpolation	http	cname.domain.tld		/		26.739 ns	0.38	0.0038	72 B	0.13
String_Create	http	cname.domain.tld		/		8.194 ns	0.12	0.0038	72 B	0.13
StringBuilder	http	cname.domain.tld		/	?para(...)alue3 [42]	98.486 ns	1.00	0.0446	840 B	1.00
String_Interpolation	http	cname.domain.tld		/	?para(...)alue3 [42]	31.592 ns	0.32	0.0085	160 B	0.19
String_Create	http	cname.domain.tld		/	?para(...)alue3 [42]	15.580 ns	0.16	0.0085	160 B	0.19
StringBuilder	http	cname.domain.tld		/path/one/two/three		80.926 ns	1.00	0.0314	592 B	1.00
String_Interpolation	http	cname.domain.tld		/path/one/two/three		27.104 ns	0.34	0.0059	112 B	0.19
String_Create	http	cname.domain.tld		/path/one/two/three		10.069 ns	0.12	0.0059	112 B	0.19
StringBuilder	http	cname.domain.tld		/path/one/two/three	?para(...)alue3 [42]	100.374 ns	1.00	0.0467	880 B	1.00
String_Interpolation	http	cname.domain.tld		/path/one/two/three	?para(...)alue3 [42]	32.507 ns	0.32	0.0102	192 B	0.22
String_Create	http	cname.domain.tld		/path/one/two/three	?para(...)alue3 [42]	15.831 ns	0.16	0.0102	192 B	0.22
StringBuilder	http	cname.domain.tld	/base-path	/		71.221 ns	1.00	0.0305	576 B	1.00
String_Interpolation	http	cname.domain.tld	/base-path	/		25.770 ns	0.36	0.0051	96 B	0.17
String_Create	http	cname.domain.tld	/base-path	/		11.728 ns	0.16	0.0051	96 B	0.17
StringBuilder	http	cname.domain.tld	/base-path	/	?para(...)alue3 [42]	101.443 ns	1.00	0.0459	864 B	1.00
String_Interpolation	http	cname.domain.tld	/base-path	/	?para(...)alue3 [42]	31.538 ns	0.31	0.0093	176 B	0.20
String_Create	http	cname.domain.tld	/base-path	/	?para(...)alue3 [42]	17.074 ns	0.17	0.0093	176 B	0.20
StringBuilder	http	cname.domain.tld	/base-path	/path/one/two/three		76.368 ns	1.00	0.0327	616 B	1.00
String_Interpolation	http	cname.domain.tld	/base-path	/path/one/two/three		27.561 ns	0.36	0.0068	128 B	0.21
String_Create	http	cname.domain.tld	/base-path	/path/one/two/three		11.338 ns	0.15	0.0068	128 B	0.21
StringBuilder	http	cname.domain.tld	/base-path	/path/one/two/three	?para(...)alue3 [42]	97.275 ns	1.00	0.0479	904 B	1.00
String_Interpolation	http	cname.domain.tld	/base-path	/path/one/two/three	?para(...)alue3 [42]	34.144 ns	0.35	0.0114	216 B	0.24
String_Create	http	cname.domain.tld	/base-path	/path/one/two/three	?para(...)alue3 [42]	17.378 ns	0.18	0.0115	216 B	0.24

StringBuilder

This benchmark uses the same implementation as UriHelper.GetDisplayUrl.

String_Interpolation

This benchmark uses string interpolation to build the URL.

String_Create

This benchmark uses String.Create and spans to build the URL.

Code

[MemoryDiagnoser]
[HideColumns("Error", "StdDev", "Median", "RatioSD")]
public class DisplayUrlBenchmark
{
    private static readonly string SchemeDelimiter = Uri.SchemeDelimiter;

    private static readonly string[] schemes = ["http"];
    private static readonly string[] hosts = ["cname.domain.tld"];
    private static readonly string[] basePaths = [null, "/base-path",];
    private static readonly string[] paths = ["/", "/path/one/two/three",];
    private static readonly string[] queries = [null, "?param1=value1&param2=value2&param3=value3",];

    public IEnumerable<object[]> Data()
    {
        foreach (var scheme in schemes)
        {
            foreach (var host in hosts)
            {
                foreach (var basePath in basePaths)
                {
                    foreach (var path in paths)
                    {
                        foreach (var query in queries)
                        {
                            yield return new object[] { scheme, new HostString(host), new PathString(basePath), new PathString(path), new QueryString(query), };
                        }
                    }
                }
            }
        }
    }

    [Benchmark(Baseline = true)]
    [ArgumentsSource(nameof(Data))]
    public string StringBuilder(string scheme, HostString host, PathString basePath, PathString path, QueryString query)
    {
        var schemeValue = scheme ?? string.Empty;
        var hostValue = host.Value ?? string.Empty;
        var basePathValue = basePath.Value ?? string.Empty;
        var pathValue = path.Value ?? string.Empty;
        var queryValue = query.Value ?? string.Empty;

        var length =
            +schemeValue.Length
            + SchemeDelimiter
            + hostValue.Length
            + basePathValue.Length
            + pathValue.Length
            + queryValue.Length;

        return new StringBuilder(length)
                .Append(schemeValue)
                .Append(SchemeDelimiter)
                .Append(hostValue)
                .Append(basePathValue)
                .Append(pathValue)
                .Append(queryValue)
                .ToString();
    }

    [Benchmark]
    [ArgumentsSource(nameof(Data))]
    public string String_Interpolation(string scheme, HostString host, PathString basePath, PathString path, QueryString query)
    {
        return $"{scheme}://{host.Value}{basePath.Value}{path.Value}{query.Value}";
    }

    [Benchmark]
    [ArgumentsSource(nameof(Data))]
    public string String_Create(string scheme, HostString host, PathString basePath, PathString path, QueryString query)
    {
        var schemeValue = scheme ?? string.Empty;
        var hostValue = host.Value ?? string.Empty;
        var basePathValue = basePath.Value ?? string.Empty;
        var pathValue = path.Value ?? string.Empty;
        var queryValue = query.Value ?? string.Empty;

        var length =
            +schemeValue.Length
            + SchemeDelimiter.Length
            + hostValue.Length
            + basePathValue.Length
            + pathValue.Length
            + queryValue.Length;

        return string.Create(
            length,
            (schemeValue, hostValue, basePathValue, pathValue, queryValue),
            static (buffer, uriParts) =>
            {
                var (scheme, host, basePath, path, query) = uriParts;

                if (scheme.Length > 0)
                {
                    scheme.CopyTo(buffer);
                    buffer = buffer.Slice(scheme.Length);
                }

                SchemeDelimiter.CopyTo(buffer);
                buffer = buffer.Slice(SchemeDelimiter.Length);

                if (host.Length > 0)
                {
                    host.CopyTo(buffer);
                    buffer = buffer.Slice(host.Length);
                }

                if (basePath.Length > 0)
                {
                    basePath.CopyTo(buffer);
                    buffer = buffer.Slice(basePath.Length);
                }

                if (path.Length > 0)
                {
                    path.CopyTo(buffer);
                    buffer = buffer.Slice(path.Length);
                }

                if (query.Length > 0)
                {
                    query.CopyTo(buffer);
                }
            });
    }
}

We've moved this issue to the Backlog milestone. This means that it is not going to be worked on for the coming release. We will reassess the backlog following the current release and consider this item at that time. To learn more about our issue management process and to have better expectation regarding different types of issues you can read our Triage Process.