AssemblyScanner improvements

[danielmarbach]

• Fixes AssemblyScanning exclusion list slows down the endpoint startup #6820

Improves the assembly scanner performance in "regular cases" slightly and in cases when the exclusion list is larger, up to 4 times.

I was doing some investigations for a customer that mentioned they are seeing slow startup times in their rather large solution. Once I was able to get my hands on the profiler data it was apparent that the IsExcluded check is the culprit.

Scenarios

I have created a solution generator that allows simulating arbitrary solution sizes. As a reference point, I created a solution with roughly 960 projects and more than 140K types.

Without Exclusions

Before

After

With a larger number of exclusions

Before

Here is the excerpt from the customer callstack

After

Benchmarks

Attribute.GetCustomAttribute

Method	Mean	Error	StdDev	Median	Ratio	RatioSD
Type	1,148.2 ns	135.51 ns	386.63 ns	1,010.9 ns	1.00	0.00
AttributeBased	804.7 ns	12.05 ns	11.27 ns	801.7 ns	0.99	0.20

Matching Strings

Method	Input	Mean	Error	StdDev	Ratio	Gen 0	Allocated
MatchOriginal	SomeAssembly	146.94 ns	0.815 ns	0.680 ns	1.00	0.0010	96 B
MatchOptimized	SomeAssembly	28.90 ns	0.441 ns	0.368 ns	0.20	-	-
MatchOptimizedHashSet	SomeAssembly	17.72 ns	0.057 ns	0.047 ns	0.12	-	-
MatchOriginal	SomeAssembly.Dll	149.63 ns	2.527 ns	2.363 ns	1.00	0.0024	208 B
MatchOptimized	SomeAssembly.Dll	59.56 ns	0.504 ns	0.447 ns	0.40	0.0011	96 B
MatchOptimizedHashSet	SomeAssembly.Dll	11.01 ns	0.106 ns	0.089 ns	0.07	-	-
MatchOriginal	SomeAssembly.Exe	184.95 ns	1.662 ns	1.473 ns	1.00	0.0024	208 B
MatchOptimized	SomeAssembly.Exe	72.69 ns	0.963 ns	0.901 ns	0.39	0.0011	96 B
MatchOptimizedHashSet	SomeAssembly.Exe	10.87 ns	0.038 ns	0.036 ns	0.06	-	-

PublicKeyValidation

Method	Mean	Error	StdDev	Ratio	Gen 0	Allocated
Before	1,157.2 ns	13.39 ns	12.53 ns	1.00	0.0687	432 B
After	842.8 ns	7.07 ns	5.90 ns	0.73	0.0277	176 B

[danielmarbach]

Once the PR is reviewed, I would want to patch 92da68a on current supported versions

[timbussmann]

some minor suggestions

[danielmarbach]

@timbussmann I think I addressed all the comments

[bording]

Left a comment about a comment (hah!) and pushed up a few minor tweaks.

This is a massive improvement!