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Cache parameter writer lookups #24536

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Merged
merged 3 commits into from
Aug 3, 2020
Merged

Cache parameter writer lookups #24536

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75ff200
Cache parameter writer lookups
SteveSandersonMS Aug 3, 2020
a08a27d
CR: Use ReferenceEqualityComparer
SteveSandersonMS Aug 3, 2020
de38540
Clean up
SteveSandersonMS Aug 3, 2020
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47 changes: 40 additions & 7 deletions src/Components/Components/src/Reflection/ComponentProperties.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -41,7 +41,7 @@ public static void SetProperties(in ParameterView parameters, object target)
foreach (var parameter in parameters)
{
var parameterName = parameter.Name;
if (!writers.WritersByName.TryGetValue(parameterName, out var writer))
if (!writers.TryGetValue(parameterName, out var writer))
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One additional optimization we could make is to stash the the WritesForType as an internal property on ComponentBase and avoid the dictionary lookup there.

if (target is ComponentBase component)
{
  component.Writer ?? = new WritersForType(targetType);
  _writer = component.Writer;
}
else
{
 // old code
}

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Thanks for the suggestion. Since this didn't show up in the profile traces as a hot path, I'd prefer not to add an optimization for it.

I guess that doing the lookup for this dictionary is relatively cheap because component.GetHashCode() is much cheaper than computing a string hash.

{
// Case 1: There is nowhere to put this value.
ThrowForUnknownIncomingParameterName(targetType, parameterName);
Expand Down Expand Up @@ -82,7 +82,7 @@ public static void SetProperties(in ParameterView parameters, object target)
isCaptureUnmatchedValuesParameterSetExplicitly = true;
}

if (writers.WritersByName.TryGetValue(parameterName, out var writer))
if (writers.TryGetValue(parameterName, out var writer))
{
if (!writer.Cascading && parameter.Cascading)
{
Expand Down Expand Up @@ -245,9 +245,15 @@ private static void ThrowForInvalidCaptureUnmatchedValuesParameterType(Type targ

private class WritersForType
{
private const int MaxCachedWriterLookups = 100;
private readonly Dictionary<string, IPropertySetter> _underlyingWriters;
private readonly ConcurrentDictionary<string, IPropertySetter?> _referenceEqualityWritersCache;

public WritersForType(Type targetType)
{
WritersByName = new Dictionary<string, IPropertySetter>(StringComparer.OrdinalIgnoreCase);
_underlyingWriters = new Dictionary<string, IPropertySetter>(StringComparer.OrdinalIgnoreCase);
_referenceEqualityWritersCache = new ConcurrentDictionary<string, IPropertySetter?>(ReferenceEqualityComparer.Instance);

foreach (var propertyInfo in GetCandidateBindableProperties(targetType))
{
var parameterAttribute = propertyInfo.GetCustomAttribute<ParameterAttribute>();
Expand All @@ -267,14 +273,14 @@ public WritersForType(Type targetType)

var propertySetter = MemberAssignment.CreatePropertySetter(targetType, propertyInfo, cascading: cascadingParameterAttribute != null);

if (WritersByName.ContainsKey(propertyName))
if (_underlyingWriters.ContainsKey(propertyName))
{
throw new InvalidOperationException(
$"The type '{targetType.FullName}' declares more than one parameter matching the " +
$"name '{propertyName.ToLowerInvariant()}'. Parameter names are case-insensitive and must be unique.");
}

WritersByName.Add(propertyName, propertySetter);
_underlyingWriters.Add(propertyName, propertySetter);

if (parameterAttribute != null && parameterAttribute.CaptureUnmatchedValues)
{
Expand All @@ -298,11 +304,38 @@ public WritersForType(Type targetType)
}
}

public Dictionary<string, IPropertySetter> WritersByName { get; }

public IPropertySetter? CaptureUnmatchedValuesWriter { get; }

public string? CaptureUnmatchedValuesPropertyName { get; }

public bool TryGetValue(string parameterName, [MaybeNullWhen(false)] out IPropertySetter writer)
{
// In intensive parameter-passing scenarios, one of the most expensive things we do is the
// lookup from parameterName to writer. Pre-5.0 that was because of the string hashing.
// To optimize this, we now have a cache in front of the lookup which is keyed by parameterName's
// object identity (not its string hash). So in most cases we can resolve the lookup without
// having to hash the string. We only fall back on hashing the string if the cache gets full,
// which would only be in very unusual situations because components don't typically have many
// parameters, and the parameterName strings usually come from compile-time constants.
if (!_referenceEqualityWritersCache.TryGetValue(parameterName, out writer))
{
_underlyingWriters.TryGetValue(parameterName, out writer);

// Note that because we're not locking around this, it's possible we might
// actually write more than MaxCachedWriterLookups entries due to concurrent
// writes. However this won't cause any problems.
// Also note that the value we're caching might be 'null'. It's valid to cache
// lookup misses just as much as hits, since then we can more quickly identify
// incoming values that don't have a corresponding writer and thus will end up
// being passed as catch-all parameter values.
if (_referenceEqualityWritersCache.Count < MaxCachedWriterLookups)
{
_referenceEqualityWritersCache.TryAdd(parameterName, writer);
}
}

return writer != null;
}
}
}
}