Improve Enum function performance (TryParse, ToString, Parse, etc...)

[tkreindler]

Description

Although the Enum code performance has been greatly improved throughout .NET Core and a lot of the worst offenders (HasFlag) have been improved there are still clearly performance gains to be had. In our MSInternal service we still use a home brewed EnumHelper class for our frequent use of TryParse and ToString. Although performance on the default implementations has improved in recent .NET versions it's still significantly less performant as our home brewed solution and even slower compared to some widely available libraries I've also tested FastEnum and Enums.NET. The downside of including such libraries are the same as always, increasing complexity of dependency graphs and the question of ownership and maintainability.

Configuration

Production scenario:
net6.0
Windows Server Evergreen
x64
Various

Benchmarking scenario:
net6.0 and net7.0 as labeled
Windows 11 22H2
x64
i7 8700k

Regression?

No

Data

These charts contain four different paths, the default .NET functions, our homebrewed solution that involves a little caching on top of the default implementation, and then the paths of two libraries FastEnum and Enums.NET. The Parse methods include two tests for each, one where a string is provided and one where only a ReadOnlySpan is provided so implementations that can work well with spans are preferred.

ToString net6.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
Default	5,772.3 us	115.05 us	127.88 us	585.9375	203.1250	203.1250	3125.82 KB
EnumHelper	679.0 us	6.74 us	6.30 us	179.6875	179.6875	179.6875	781.42 KB
FastEnum	633.7 us	8.35 us	7.41 us	181.6406	181.6406	181.6406	781.39 KB
EnumsDotnet	664.7 us	9.78 us	9.14 us	181.6406	181.6406	181.6406	781.38 KB

ToString net7.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
Default	4,859.5 us	86.12 us	199.59 us	562.5000	187.5000	187.5000	3125.69 KB
EnumHelper	736.1 us	7.41 us	6.93 us	179.6875	179.6875	179.6875	781.4 KB
FastEnum	747.4 us	14.82 us	27.48 us	181.6406	181.6406	181.6406	781.42 KB
EnumsDotnet	779.1 us	14.32 us	20.54 us	181.6406	181.6406	181.6406	781.4 KB

Parse net6.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
.NET Default Parse(String)	7.005 ms	0.1261 ms	0.2071 ms	78.1250	78.1250	78.1250	390.81 KB
Home brewed Parse(String)	3.833 ms	0.0741 ms	0.0854 ms	101.5625	101.5625	101.5625	390.73 KB
FastEnum Parse(String)	2.724 ms	0.0542 ms	0.0580 ms	101.5625	101.5625	101.5625	390.73 KB
Enums.NET Parse(String)	3.073 ms	0.0356 ms	0.0333 ms	101.5625	101.5625	101.5625	390.73 KB
.NET Default Parse(Span)	6.840 ms	0.0797 ms	0.0745 ms	93.7500	93.7500	93.7500	390.81 KB
Home brewed Parse(Span.ToString())	4.129 ms	0.0821 ms	0.1124 ms	93.7500	93.7500	93.7500	390.73 KB
FastEnum Parse(Span.ToString())	3.036 ms	0.0596 ms	0.0586 ms	101.5625	101.5625	101.5625	390.73 KB
Enums.NET Parse(Span.ToString())	3.109 ms	0.0482 ms	0.0451 ms	101.5625	101.5625	101.5625	390.76 KB

Parse net7.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
.NET Default Parse(String)	5.533 ms	0.1095 ms	0.1499 ms	93.7500	93.7500	93.7500	390.82 KB
Home brewed Parse(String)	3.406 ms	0.0519 ms	0.0460 ms	39.0625	39.0625	39.0625	390.71 KB
FastEnum Parse(String)	2.224 ms	0.0355 ms	0.0315 ms	39.0625	39.0625	39.0625	390.71 KB
Enums.NET Parse(String)	2.848 ms	0.0545 ms	0.0535 ms	101.5625	101.5625	101.5625	390.73 KB
.NET Default Parse(Span)	5.367 ms	0.0475 ms	0.0421 ms	39.0625	39.0625	39.0625	390.75 KB
Home brewed Parse(Span.ToString())	3.547 ms	0.0369 ms	0.0345 ms	39.0625	39.0625	39.0625	390.71 KB
FastEnum Parse(Span.ToString())	2.397 ms	0.0264 ms	0.0247 ms	39.0625	39.0625	39.0625	390.71 KB
Enums.NET Parse(Span.ToString())	3.416 ms	0.0682 ms	0.0911 ms	101.5625	101.5625	101.5625	390.73 KB

Analysis

The problem almost certainly in not enough caching. All of these different solutions revolve around using reflection at runtime to look up the values of these values. The faster solutions generally use more caching to speed up performance. I'd suggest the .NET implementation either take a more aggressive approach to caching and or potentially look into using source generators to negate the startup cost associated with the caching altogether.

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[jkotas]

Could you please share sources for your benchmarks?

Note that .NET 8 has some enum performance improvements already (e.g. #78580).

Tagging subscribers to this area: @dotnet/area-system-runtime
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Issue Details

---

Description

Although the Enum code performance has been greatly improved throughout .NET Core and a lot of the worst offenders (HasFlag) have been improved there are still clearly performance gains to be had. In our MSInternal service we still use a home brewed EnumHelper class for our frequent use of TryParse and ToString. Although performance on the default implementations has improved in recent .NET versions it's still significantly less performant as our home brewed solution and even slower compared to some widely available libraries I've also tested FastEnum and Enums.NET. The downside of including such libraries are the same as always, increasing complexity of dependency graphs and the question of ownership and maintainability.

Configuration

Production scenario:
net6.0
Windows Server Evergreen
x64
Various

Benchmarking scenario:
net6.0 and net7.0 as labeled
Windows 11 22H2
x64
i7 8700k

Regression?

No

Data

These charts contain four different paths, the default .NET functions, our homebrewed solution that involves a little caching on top of the default implementation, and then the paths of two libraries FastEnum and Enums.NET. The Parse methods include two tests for each, one where a string is provided and one where only a ReadOnlySpan is provided so implementations that can work well with spans are preferred.

ToString net6.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
Default	5,772.3 us	115.05 us	127.88 us	585.9375	203.1250	203.1250	3125.82 KB
EnumHelper	679.0 us	6.74 us	6.30 us	179.6875	179.6875	179.6875	781.42 KB
FastEnum	633.7 us	8.35 us	7.41 us	181.6406	181.6406	181.6406	781.39 KB
EnumsDotnet	664.7 us	9.78 us	9.14 us	181.6406	181.6406	181.6406	781.38 KB

ToString net7.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
Default	4,859.5 us	86.12 us	199.59 us	562.5000	187.5000	187.5000	3125.69 KB
EnumHelper	736.1 us	7.41 us	6.93 us	179.6875	179.6875	179.6875	781.4 KB
FastEnum	747.4 us	14.82 us	27.48 us	181.6406	181.6406	181.6406	781.42 KB
EnumsDotnet	779.1 us	14.32 us	20.54 us	181.6406	181.6406	181.6406	781.4 KB

Parse net6.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
.NET Default Parse(String)	7.005 ms	0.1261 ms	0.2071 ms	78.1250	78.1250	78.1250	390.81 KB
Home brewed Parse(String)	3.833 ms	0.0741 ms	0.0854 ms	101.5625	101.5625	101.5625	390.73 KB
FastEnum Parse(String)	2.724 ms	0.0542 ms	0.0580 ms	101.5625	101.5625	101.5625	390.73 KB
Enums.NET Parse(String)	3.073 ms	0.0356 ms	0.0333 ms	101.5625	101.5625	101.5625	390.73 KB
.NET Default Parse(Span)	6.840 ms	0.0797 ms	0.0745 ms	93.7500	93.7500	93.7500	390.81 KB
Home brewed Parse(Span.ToString())	4.129 ms	0.0821 ms	0.1124 ms	93.7500	93.7500	93.7500	390.73 KB
FastEnum Parse(Span.ToString())	3.036 ms	0.0596 ms	0.0586 ms	101.5625	101.5625	101.5625	390.73 KB
Enums.NET Parse(Span.ToString())	3.109 ms	0.0482 ms	0.0451 ms	101.5625	101.5625	101.5625	390.76 KB

Parse net7.0

Method	Mean	Error	StdDev	Gen 0	Gen 1	Gen 2	Allocated
.NET Default Parse(String)	5.533 ms	0.1095 ms	0.1499 ms	93.7500	93.7500	93.7500	390.82 KB
Home brewed Parse(String)	3.406 ms	0.0519 ms	0.0460 ms	39.0625	39.0625	39.0625	390.71 KB
FastEnum Parse(String)	2.224 ms	0.0355 ms	0.0315 ms	39.0625	39.0625	39.0625	390.71 KB
Enums.NET Parse(String)	2.848 ms	0.0545 ms	0.0535 ms	101.5625	101.5625	101.5625	390.73 KB
.NET Default Parse(Span)	5.367 ms	0.0475 ms	0.0421 ms	39.0625	39.0625	39.0625	390.75 KB
Home brewed Parse(Span.ToString())	3.547 ms	0.0369 ms	0.0345 ms	39.0625	39.0625	39.0625	390.71 KB
FastEnum Parse(Span.ToString())	2.397 ms	0.0264 ms	0.0247 ms	39.0625	39.0625	39.0625	390.71 KB
Enums.NET Parse(Span.ToString())	3.416 ms	0.0682 ms	0.0911 ms	101.5625	101.5625	101.5625	390.73 KB

Analysis

The problem almost certainly in not enough caching. All of these different solutions revolve around using reflection at runtime to look up the values of these values. The faster solutions generally use more caching to speed up performance. I'd suggest the .NET implementation either take a more aggressive approach to caching and or potentially look into using source generators to negate the startup cost associated with the caching altogether.

Author:	tkreindler
Assignees:	-
Labels:	area-System.Runtime, tenet-performance, untriaged
Milestone:	-

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