Remove the second type parameter from CastingConverter #80755

eiriktsarpalis · 2023-01-17T22:05:28Z

The CastingConverter<TSource, TTarget> class is an internal adapter used for custom converters whose declared type doesn't match that of the serialized member they are being assigned to. The problem with the current implementation is that CastingConverter uses two type parameters, which is contributing to a quadratic explosion of generic specializations in NativeAOT:

System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Text.Json.JsonElement>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Boolean>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Byte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Char>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTime>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTimeOffset>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Decimal>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Double>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Guid>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.SByte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Single>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeSpan>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.__Canon>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.__Canon>.

This PR relaxes the implementation so that CastingConverter references and consumes the underlying converter as a weakly typed JsonConverter instance. This change can regress runtime performance in certain scenaria due to added boxing/virtual calls, but this should only impact members that are using converters polymorphically -- a relatively rare occurrence.

cc @eerhardt @jkotas

ghost · 2023-01-17T22:05:45Z

Tagging subscribers to this area: @dotnet/area-system-text-json, @gregsdennis
See info in area-owners.md if you want to be subscribed.

Issue Details

The CastingConverter<TSource, TTarget> class is an internal adapter used for custom converters whose declared type doesn't match that of the serialized member they are being assigned to. The problem with the current implementation is that CastingConverter uses two type parameters, which is contributing to a quadratic explosion of generic specializations in NativeAOT:

System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Text.Json.JsonElement>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Boolean>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Byte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Char>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTime>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTimeOffset>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Decimal>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Double>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Guid>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.SByte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Single>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeSpan>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.__Canon>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.__Canon>.

This PR relaxes the implementation so that CastingConverter references and consumes the underlying converter as a weakly typed JsonConverter instance. This change can regress runtime performance in certain scenaria due to added boxing/virtual calls, but this should only impact members that are using converters polymorphically -- a relatively rare occurrence.

cc @eerhardt

Author:	eiriktsarpalis
Assignees:	eiriktsarpalis
Labels:	`area-System.Text.Json`
Milestone:	8.0.0

eiriktsarpalis · 2023-01-17T22:10:19Z

src/libraries/System.Text.Json/src/System/Text/Json/Serialization/JsonConverter.cs

@@ -138,15 +143,20 @@ internal static bool ShouldFlush(Utf8JsonWriter writer, ref WriteStack state)
        // This is used internally to quickly determine the type being converted for JsonConverter<T>.
        internal abstract Type TypeToConvert { get; }

-        internal abstract bool OnTryReadAsObject(ref Utf8JsonReader reader, JsonSerializerOptions options, scoped ref ReadStack state, out object? value);
-        internal abstract bool TryReadAsObject(ref Utf8JsonReader reader, JsonSerializerOptions options, scoped ref ReadStack state, out object? value);
+        internal abstract object? ReadAsObject(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options);


Even though this change is adding new methods to JsonConverter this should increase code size linearly over the number of generic specializations. This should still contribute to a net decrease of code size given that CastingConverter contributes to quadratic growth over the number of types being used. I will follow up with real numbers validating this hypothesis.

eerhardt · 2023-01-17T22:13:56Z

which is contributing to a quadratic explosion of generic specializations in NativeAOT:

Is it possible to get before/after size numbers for this change? If you need a test app, the one we are using in our perf measurements is here.

eiriktsarpalis · 2023-01-18T19:10:52Z

I compared the publish AOT size for the Goldilocks app between main and the PR branch. I'm seeing a ~7MB improvement in the size of the publish folder, from 120 MB down to 113 MB.

eiriktsarpalis · 2023-01-19T17:48:32Z

STJ Numbers from the mstat dump of the Goldilocks app. Seeing just over 1MB of size reduction overall:

21156   publish-main/Goldilocks
20064   publish-pr/Goldilocks

main

// ********** Types Total Size 3,327,268
System.Text.Json                         476,148

// ********** Size By Namespace
System.Text.Json.Serialization.Converters 876,578
System.Text.Json.Serialization.Metadata  607,084
System.Text.Json.Serialization           361,833
System.Text.Json                         203,356

PR

// ********** Types Total Size 3,172,132
System.Text.Json                         320,884

// ********** Size By Namespace
System.Text.Json.Serialization.Metadata  605,298
System.Text.Json.Serialization           397,892
System.Text.Json                         208,571
System.Text.Json.Serialization.Converters 200,477

eerhardt · 2023-01-19T22:01:25Z

/benchmark json aspnet-citrine-win libs

pr-benchmarks · 2023-01-19T22:08:58Z

Benchmark started for json on aspnet-citrine-win with libs. Logs: link

eerhardt

I had a look over the code (I'm no expert in this area), but I think this is a great change. If there are no runtime perf degradations, I think this is a great NativeAOT size win (5% of the new dotnet new api -aot app).

pr-benchmarks · 2023-01-19T22:39:16Z

json - aspnet-citrine-win

application	json.base	json.pr
CPU Usage (%)	80	87	+8.75%
Cores usage (%)	2,229	2,433	+9.15%
Working Set (MB)	73	74	+1.37%
Private Memory (MB)	100	101	+1.00%
Build Time (ms)	4,979	3,287	-33.98%
Start Time (ms)	417	418	+0.24%
Published Size (KB)	96,702	96,702	0.00%
Symbols Size (KB)	52	52	0.00%
.NET Core SDK Version	8.0.100-alpha.1.23069.6	8.0.100-alpha.1.23069.6

load	json.base	json.pr
CPU Usage (%)	72	74	+2.78%
Cores usage (%)	2,026	2,084	+2.86%
Working Set (MB)	119	119	0.00%
Private Memory (MB)	363	363	0.00%
Start Time (ms)	0	0
First Request (ms)	85	85	0.00%
Requests/sec	1,059,909	1,095,251	+3.33%
Requests	16,004,210	16,537,175	+3.33%
Mean latency (ms)	0.89	1.11	+24.72%
Max latency (ms)	36.84	59.44	+61.35%
Bad responses	0	0
Socket errors	0	0
Read throughput (MB/s)	147.58	152.50	+3.33%
Latency 50th (ms)	0.32	0.31	-4.64%
Latency 75th (ms)	0.77	0.83	+8.37%
Latency 90th (ms)	2.34	3.10	+32.48%
Latency 99th (ms)	7.02	10.31	+46.87%

krwq

Awesome win, thanks!

krwq · 2023-01-20T10:11:57Z

ghost · 2023-01-20T10:25:21Z

Tagging subscribers to 'size-reduction': @eerhardt, @SamMonoRT, @marek-safar
See info in area-owners.md if you want to be subscribed.

Issue Details

The CastingConverter<TSource, TTarget> class is an internal adapter used for custom converters whose declared type doesn't match that of the serialized member they are being assigned to. The problem with the current implementation is that CastingConverter uses two type parameters, which is contributing to a quadratic explosion of generic specializations in NativeAOT:

System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Text.Json.JsonElement>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Boolean>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Byte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Char>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTime>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.DateTimeOffset>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Decimal>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Double>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Guid>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Int64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.SByte>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Single>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeOnly>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.TimeSpan>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt16>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt32>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.UInt64>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.__Canon,System.__Canon>.                                                                           384
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Text.Json.JsonElement,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Boolean,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Byte,System.__Canon>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.Collections.Generic.KeyValuePair`2<System.__Canon,System.__Canon>>.                                                                           376
System.Text.Json.Serialization.Converters.CastingConverter`2<System.Char,System.__Canon>.

This PR relaxes the implementation so that CastingConverter references and consumes the underlying converter as a weakly typed JsonConverter instance. This change can regress runtime performance in certain scenaria due to added boxing/virtual calls, but this should only impact members that are using converters polymorphically -- a relatively rare occurrence.

cc @eerhardt @jkotas

Author:	eiriktsarpalis
Assignees:	eiriktsarpalis
Labels:	`area-System.Text.Json`, `size-reduction`
Milestone:	8.0.0

Remove second type parameter from CastingConverter

d44db43

eiriktsarpalis added this to the 8.0.0 milestone Jan 17, 2023

ghost assigned eiriktsarpalis Jan 17, 2023

dotnet-issue-labeler bot added the area-System.Text.Json label Jan 17, 2023

eiriktsarpalis requested review from krwq, eerhardt and layomia January 17, 2023 22:05

eiriktsarpalis commented Jan 17, 2023

View reviewed changes

build-analysis bot mentioned this pull request Jan 18, 2023

Tracking issue for CI build timeouts #76454

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eiriktsarpalis requested a review from tarekgh January 18, 2023 17:02

eerhardt approved these changes Jan 19, 2023

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krwq approved these changes Jan 20, 2023

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krwq added the size-reduction Issues impacting final app size primary for size sensitive workloads label Jan 20, 2023

eiriktsarpalis mentioned this pull request Jan 20, 2023

Potential size reduction opportunities in System.Text.Json NativeAOT #80917

Open

eiriktsarpalis merged commit a04aaeb into dotnet:main Jan 20, 2023

eiriktsarpalis deleted the castingconverter-remove-generic-parameter branch January 20, 2023 16:15

mdh1418 pushed a commit to mdh1418/runtime that referenced this pull request Jan 24, 2023

Remove second type parameter from CastingConverter (dotnet#80755)

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Remove the second type parameter from CastingConverter #80755

Remove the second type parameter from CastingConverter #80755

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Remove the second type parameter from CastingConverter #80755

Remove the second type parameter from CastingConverter #80755

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