[WIP] Performance improvements

[martincostello]

Changes

Apply some performance improvements suggested by Copilot after prompting it to look for quick wins.

For now these are just for review to see what people think - some of the improvements seem like gains, but some of the others might be trying to get gains at the expense of functional correctness.

For any changes that seem correct and worth taking, I can split them out into separate PRs as the files touch 3 different projects.

For any changes that didn't seem to be covered by existing benchmarks, new benchmarks have been added.

Benchmark results

Copilot Summary

Suite	Rows	Duration Δ	Duration ratio	Allocation Δ	Allocation ratio
Benchmarks.Context.BaggageBenchmarks	15	-89.42%	0.11x	-55.51%	0.45x
Benchmarks.Context.Propagation.BaggagePropagatorBenchmarks	12	-1.41%	0.99x	0.00%	1.00x
Benchmarks.Context.Propagation.TraceContextPropagatorBenchmarks	6	-1.29%	0.99x	0.00%	1.00x
Benchmarks.Exporter.OtlpMetricExporterBenchmarks	2	-2.75%	0.97x	0.00%	1.00x
Benchmarks.Metrics.HistogramAdviceBenchmarks	6	-1.14%	0.99x	-0.02%	1.00x

Expand to see

main + the new benchmarks

BaggageBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ItemCount	Mean	Error	StdDev	Median	Gen0	Allocated
SetBaggageNoOp	1	26.00 ns	0.493 ns	0.437 ns	26.13 ns	0.0198	248 B
SetBaggageSingleUpdate	1	25.01 ns	0.205 ns	0.192 ns	25.00 ns	0.0198	248 B
RemoveMissingBaggage	1	18.76 ns	0.226 ns	0.212 ns	18.70 ns	0.0172	216 B
EqualsSameBackingStore	1	56.00 ns	0.420 ns	0.393 ns	55.94 ns	0.0172	216 B
EqualsEquivalentContents	1	103.85 ns	0.884 ns	0.827 ns	104.05 ns	0.0172	216 B
SetBaggageNoOp	5	95.44 ns	13.875 ns	40.909 ns	64.92 ns	0.0286	360 B
SetBaggageSingleUpdate	5	65.78 ns	0.784 ns	0.733 ns	65.86 ns	0.0286	360 B
RemoveMissingBaggage	5	39.66 ns	0.355 ns	0.332 ns	39.68 ns	0.0261	328 B
EqualsSameBackingStore	5	249.46 ns	1.939 ns	1.813 ns	249.89 ns	0.0501	632 B
EqualsEquivalentContents	5	254.07 ns	2.531 ns	2.368 ns	253.79 ns	0.0501	632 B
SetBaggageNoOp	20	227.84 ns	2.010 ns	1.782 ns	228.30 ns	0.0644	808 B
SetBaggageSingleUpdate	20	229.16 ns	1.471 ns	1.304 ns	229.21 ns	0.0644	808 B
RemoveMissingBaggage	20	113.47 ns	0.847 ns	0.792 ns	113.57 ns	0.0618	776 B
EqualsSameBackingStore	20	922.83 ns	4.654 ns	4.354 ns	923.58 ns	0.1745	2192 B
EqualsEquivalentContents	20	903.11 ns	13.282 ns	11.774 ns	902.23 ns	0.1745	2192 B

BaggagePropagatorBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ItemCount	UseSpecialChars	Mean	Error	StdDev	Gen0	Gen1	Allocated
Extract	1	False	49.09 ns	0.642 ns	0.569 ns	0.0274	-	344 B
Inject	1	False	33.45 ns	0.684 ns	0.814 ns	0.0121	-	152 B
Extract	1	True	144.50 ns	2.626 ns	2.456 ns	0.0618	-	776 B
Inject	1	True	99.29 ns	1.494 ns	1.397 ns	0.0343	-	432 B
Extract	5	False	179.26 ns	3.126 ns	2.924 ns	0.0701	0.0002	880 B
Inject	5	False	122.88 ns	0.479 ns	0.400 ns	0.0389	-	488 B
Extract	5	True	689.59 ns	12.110 ns	10.113 ns	0.2422	0.0010	3040 B
Inject	5	True	391.63 ns	7.153 ns	6.341 ns	0.1535	-	1928 B
Extract	20	False	648.01 ns	5.723 ns	4.779 ns	0.2842	0.0048	3576 B
Inject	20	False	400.14 ns	6.546 ns	5.803 ns	0.1593	0.0005	2000 B
Extract	20	True	2,726.30 ns	25.085 ns	23.464 ns	0.9766	0.0229	12296 B
Inject	20	True	1,512.12 ns	13.904 ns	11.610 ns	0.5436	0.0038	6832 B

TraceContextPropagatorBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	LongListMember	MembersCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Extract	False	0	81.50 ns	1.153 ns	1.079 ns	1.00	0.02	0.0312	-	392 B	1.00
Extract	False	4	369.72 ns	6.632 ns	6.204 ns	1.00	0.02	0.1783	0.0010	2240 B	1.00
Extract	False	32	2,020.38 ns	29.656 ns	27.740 ns	1.00	0.02	0.9804	-	12312 B	1.00
Extract	True	0	86.94 ns	0.513 ns	0.428 ns	1.00	0.01	0.0312	-	392 B	1.00
Extract	True	4	2,103.91 ns	40.700 ns	57.056 ns	1.00	0.04	1.2283	0.0496	15456 B	1.00
Extract	True	32	14,382.64 ns	119.399 ns	105.844 ns	1.00	0.01	8.0261	1.6022	100792 B	1.00

OtlpMetricExporterBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
ExportCounterWithScalarTags	52.47 μs	0.984 μs	1.093 μs	0.3662	0.2441	5.31 KB
ExportHistogramWithFilteredArrayTags	49.37 μs	0.575 μs	0.510 μs	0.3662	0.2441	5.38 KB

HistogramAdviceBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ValueType	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
BuildProviderAndCollect	Byte	196.4 μs	3.77 μs	5.04 μs	45.4102	45.4102	45.4102	264.54 KB
BuildProviderAndCollect	Double	184.9 μs	3.59 μs	4.28 μs	45.4102	45.4102	45.4102	264.57 KB
BuildProviderAndCollect	Int16	181.2 μs	3.44 μs	3.22 μs	45.4102	45.4102	45.4102	264.55 KB
BuildProviderAndCollect	Int32	176.2 μs	3.49 μs	4.28 μs	45.4102	45.4102	45.4102	264.58 KB
BuildProviderAndCollect	Int64	182.8 μs	3.59 μs	5.14 μs	45.4102	45.4102	45.4102	264.59 KB
BuildProviderAndCollect	Single	183.5 μs	3.67 μs	7.97 μs	45.4102	45.4102	45.4102	264.67 KB

This PR

BaggageBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ItemCount	Mean	Error	StdDev	Gen0	Allocated
SetBaggageNoOp	1	7.8334 ns	0.1777 ns	0.1975 ns	0.0025	32 B
SetBaggageSingleUpdate	1	32.2689 ns	0.6238 ns	0.5530 ns	0.0197	248 B
RemoveMissingBaggage	1	2.2039 ns	0.0539 ns	0.0504 ns	-	-
EqualsSameBackingStore	1	0.1991 ns	0.0033 ns	0.0029 ns	-	-
EqualsEquivalentContents	1	55.7622 ns	0.7667 ns	0.7171 ns	0.0172	216 B
SetBaggageNoOp	5	26.3823 ns	0.2482 ns	0.2321 ns	0.0025	32 B
SetBaggageSingleUpdate	5	67.2756 ns	0.8569 ns	0.8015 ns	0.0286	360 B
RemoveMissingBaggage	5	2.9260 ns	0.0413 ns	0.0366 ns	-	-
EqualsSameBackingStore	5	0.1990 ns	0.0030 ns	0.0027 ns	-	-
EqualsEquivalentContents	5	249.5908 ns	2.7217 ns	2.5459 ns	0.0501	632 B
SetBaggageNoOp	20	96.9302 ns	0.6843 ns	0.6401 ns	0.0025	32 B
SetBaggageSingleUpdate	20	211.5347 ns	1.8282 ns	1.7101 ns	0.0644	808 B
RemoveMissingBaggage	20	2.1998 ns	0.0325 ns	0.0304 ns	-	-
EqualsSameBackingStore	20	0.2016 ns	0.0071 ns	0.0066 ns	-	-
EqualsEquivalentContents	20	886.0641 ns	6.8063 ns	6.3666 ns	0.1745	2192 B

BaggagePropagatorBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ItemCount	UseSpecialChars	Mean	Error	StdDev	Gen0	Gen1	Allocated
Extract	1	False	53.04 ns	0.908 ns	0.805 ns	0.0274	-	344 B
Inject	1	False	36.35 ns	0.750 ns	0.802 ns	0.0121	-	152 B
Extract	1	True	146.15 ns	2.875 ns	2.953 ns	0.0618	-	776 B
Inject	1	True	93.16 ns	1.702 ns	3.154 ns	0.0343	-	432 B
Extract	5	False	175.45 ns	1.752 ns	1.639 ns	0.0701	0.0002	880 B
Inject	5	False	113.23 ns	1.095 ns	1.024 ns	0.0389	-	488 B
Extract	5	True	626.48 ns	3.350 ns	2.970 ns	0.2422	0.0010	3040 B
Inject	5	True	392.10 ns	4.194 ns	3.923 ns	0.1535	-	1928 B
Extract	20	False	645.88 ns	3.673 ns	3.436 ns	0.2842	0.0048	3576 B
Inject	20	False	395.95 ns	3.000 ns	2.659 ns	0.1593	0.0005	2000 B
Extract	20	True	2,656.33 ns	52.381 ns	58.221 ns	0.9766	0.0229	12296 B
Inject	20	True	1,451.26 ns	13.755 ns	12.194 ns	0.5436	0.0038	6832 B

TraceContextPropagatorBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	LongListMember	MembersCount	Mean	Error	StdDev	Ratio	RatioSD	Gen0	Gen1	Allocated	Alloc Ratio
Extract	False	0	88.32 ns	0.537 ns	0.503 ns	1.00	0.01	0.0312	-	392 B	1.00
Extract	False	4	360.15 ns	7.172 ns	13.114 ns	1.00	0.05	0.1783	0.0010	2240 B	1.00
Extract	False	32	1,932.38 ns	11.855 ns	10.510 ns	1.00	0.01	0.9804	-	12312 B	1.00
Extract	True	0	86.34 ns	0.504 ns	0.447 ns	1.00	0.01	0.0312	-	392 B	1.00
Extract	True	4	1,987.34 ns	14.029 ns	12.437 ns	1.00	0.01	1.2283	0.0496	15456 B	1.00
Extract	True	32	14,048.96 ns	111.334 ns	104.142 ns	1.00	0.01	8.0261	1.6022	100792 B	1.00

OtlpMetricExporterBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	Mean	Error	StdDev	Gen0	Gen1	Allocated
ExportCounterWithScalarTags	49.88 μs	0.511 μs	0.453 μs	0.3662	0.2441	5.31 KB
ExportHistogramWithFilteredArrayTags	49.12 μs	0.459 μs	0.430 μs	0.3662	0.2441	5.38 KB

HistogramAdviceBenchmarks

BenchmarkDotNet v0.15.8, Windows 11 (10.0.26200.8117/25H2/2025Update/HudsonValley2)
13th Gen Intel Core i7-13700H 2.90GHz, 1 CPU, 20 logical and 14 physical cores
.NET SDK 10.0.201
  [Host]     : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3
  DefaultJob : .NET 10.0.5 (10.0.5, 10.0.526.15411), X64 RyuJIT x86-64-v3

Method	ValueType	Mean	Error	StdDev	Gen0	Gen1	Gen2	Allocated
BuildProviderAndCollect	Byte	192.9 μs	1.88 μs	3.49 μs	45.4102	45.4102	45.4102	264.52 KB
BuildProviderAndCollect	Double	180.9 μs	3.56 μs	4.51 μs	45.4102	45.4102	45.4102	264.54 KB
BuildProviderAndCollect	Int16	179.0 μs	3.34 μs	4.22 μs	45.4102	45.4102	45.4102	264.51 KB
BuildProviderAndCollect	Int32	180.6 μs	3.51 μs	5.96 μs	45.4102	45.4102	45.4102	264.51 KB
BuildProviderAndCollect	Int64	174.7 μs	3.44 μs	3.68 μs	45.4102	45.4102	45.4102	264.51 KB
BuildProviderAndCollect	Single	184.2 μs	3.62 μs	7.87 μs	45.4102	45.4102	45.4102	264.62 KB

Merge requirement checklist

• CONTRIBUTING guidelines followed (license requirements, nullable enabled, static analysis, etc.)
• Unit tests added/updated
• Appropriate CHANGELOG.md files updated for non-trivial changes
• Changes in public API reviewed (if applicable)

[codecov]

Codecov Report

❌ Patch coverage is 85.96491% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 88.54%. Comparing base (a2b6372) to head (1fe016b).
⚠️ Report is 37 commits behind head on main.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
src/OpenTelemetry/Metrics/MetricStreamIdentity.cs	80.00%	6 Missing ⚠️
...mentation/ExportClient/Grpc/GrpcProtocolHelpers.cs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7071      +/-   ##
==========================================
- Coverage   88.54%   88.54%   -0.01%     
==========================================
  Files         270      270              
  Lines       12884    12935      +51     
==========================================
+ Hits        11408    11453      +45     
- Misses       1476     1482       +6     

Flag	Coverage Δ
unittests-Project-Experimental	88.34% <85.96%> (-0.11%)	⬇️
unittests-Project-Stable	88.23% <85.96%> (-0.24%)	⬇️
unittests-Solution	88.51% <85.96%> (-0.01%)	⬇️
unittests-UnstableCoreLibraries-Experimental	40.87% <3.63%> (-0.79%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
src/OpenTelemetry.Api/Baggage.cs	100.00% <100.00%> (ø)
src/OpenTelemetry/ReadOnlyFilteredTagCollection.cs	100.00% <100.00%> (ø)
...mentation/ExportClient/Grpc/GrpcProtocolHelpers.cs	62.50% <0.00%> (+11.21%)	⬆️
src/OpenTelemetry/Metrics/MetricStreamIdentity.cs	87.36% <80.00%> (-5.14%)	⬇️

... and 5 files with indirect coverage changes

[martincostello]

Should compare the numbers for net462, because the code looks identical, but there's probably a reason it differs other than just where the TryGet() is getting values from.