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Avoid allocating the CandidateSet when there's a single match #9622

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Merged
davidfowl merged 3 commits into from
Apr 22, 2019
Merged

Avoid allocating the CandidateSet when there's a single match #9622

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337fcae
Avoid allocating the CandidateSet when there's a single match
davidfowl Apr 21, 2019
ae20d99
Remove RVD allocation in the fast path
davidfowl Apr 21, 2019
cd3d266
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davidfowl Apr 22, 2019
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29 changes: 25 additions & 4 deletions src/Http/Routing/src/Matching/DfaMatcher.cs
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
// Copyright (c) .NET Foundation. All rights reserved.
// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
Expand Down Expand Up @@ -53,7 +53,8 @@ public sealed override Task MatchAsync(HttpContext httpContext, EndpointSelector
// FindCandidateSet will process the DFA and return a candidate set. This does
// some preliminary matching of the URL (mostly the literal segments).
var (candidates, policies) = FindCandidateSet(httpContext, path, segments);
if (candidates.Length == 0)
var candidateCount = candidates.Length;
if (candidateCount == 0)
{
if (log)
{
Expand All @@ -68,6 +69,26 @@ public sealed override Task MatchAsync(HttpContext httpContext, EndpointSelector
Logger.CandidatesFound(_logger, path, candidates);
}

var policyCount = policies.Length;

// This is a fast path for single candidate, 0 policies and default selector
if (policyCount == 0 && candidateCount == 1 && _selector is DefaultEndpointSelector)
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{
ref var candidate = ref candidates[0];
var flags = candidate.Flags;
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// Just strict path matching
if (flags == Candidate.CandidateFlags.None)
{
// TODO: Remove this allocation
context.RouteValues = new RouteValueDictionary();
context.Endpoint = candidate.Endpoint;

// We're done
return Task.CompletedTask;
}
}

// At this point we have a candidate set, defined as a list of endpoints in
// priority order.
//
Expand All @@ -83,7 +104,7 @@ public sealed override Task MatchAsync(HttpContext httpContext, EndpointSelector
// `candidateSet` is the mutable state that we pass to the EndpointSelector.
var candidateSet = new CandidateSet(candidates);

for (var i = 0; i < candidates.Length; i++)
for (var i = 0; i < candidateCount; i++)
{
// PERF: using ref here to avoid copying around big structs.
//
Expand Down Expand Up @@ -165,7 +186,7 @@ public sealed override Task MatchAsync(HttpContext httpContext, EndpointSelector
}
}

if (policies.Length == 0)
if (policyCount == 0)
{
// Perf: avoid a state machine if there are no polices
return _selector.SelectAsync(httpContext, context, candidateSet);
Expand Down