放弃 AutoMapper ，拥抱 Mapster
性能测试结论：使用
new {}的方式性能最佳，其次是Mapster，最后是AutoMapper
最近在对一个业务接口做代码重构时，发现在使用 AutoMapper 做对象转换时，接口响应速度极慢，100多条数据，请求时长都超过了8秒。为了找出原因所在，我尝试将 EF Core 的相关查询和 实体转换拆分开来做分析，最终发现是由于使用 AutoMapper 时，性能出现了瓶颈。于是我尝试使用 select new {} 的 Linq 方式来硬编码转换，发现效率提升了几倍，基本 2秒内就能完成。出于好奇，我尝试对 AutoMapper 做一下性能对比测试。
测试步骤
测试环境
- OS：Windows 10.0.19042.1348 (20H2/October2020Update)
- CPU：Intel Core i5-7500 CPU 3.40GHz (Kaby Lake), 1 CPU, 4 logical and 4 physical cores
- SDK：NET SDK=6.0.100
- 压测工具：BenchmarkDotNet=v0.13.1
创建项目
dotnet new console -o ConsoleApp1
安装依赖包
dotnet add package BenchmarkDotNet --version 0.13.1
dotnet add package AutoMapper --version 10.1.1
dotnet add package Mapster --version 7.2.0
定义用于测试 Entity 和 DTO
public enum MyEnum
{
[Description("进行中")]
Doing,
[Description("完成")]
Done
}
public class Entity
{
public int Id { get; set; }
public Guid Oid { get; set; }
public string? NickName { get; set; }
public bool Created { get; set; }
public MyEnum State { get; set; }
}
public class EntityDto
{
public int Id { get; set; }
public Guid Oid { get; set; }
public string? NickName { get; set; }
public bool Created { get; set; }
public MyEnum Enum { get; set; }
public string? EnumString { get; set; }
}
配置 Entity 和 DTO 之间的转换关系
AutoMapper 配置
public class AutoMapperProfile : Profile
{
public AutoMapperProfile()
{
CreateMap<Entity, EntityDto>()
.ForMember(dest => dest.Id, opt => opt.MapFrom(src => src.Id))
.ForMember(dest => dest.Oid, opt => opt.MapFrom(src => src.Oid))
.ForMember(dest => dest.NickName, opt => opt.MapFrom(src => src.NickName))
.ForMember(dest => dest.Created, opt => opt.MapFrom(src => src.Created))
.ForMember(dest => dest.Enum, opt => opt.MapFrom(src => src.State))
.ForMember(dest => dest.EnumString, opt => opt.MapFrom(src => src.State.GetDescription()));
}
}
Mapster 配置
public class MapsterProfile : TypeAdapterConfig
{
public MapsterProfile()
{
ForType<Entity, EntityDto>()
.Map(dest => dest.Id, src => src.Id)
.Map(dest => dest.Oid, src => src.Oid)
.Map(dest => dest.NickName, src => src.NickName)
.Map(dest => dest.Created, src => src.Created)
.Map(dest => dest.Enum, src => src.State)
.Map(dest => dest.EnumString, src => src.State.GetDescription());
}
}
创建性能测试类
public class PerformanceTest
{
private IReadOnlyList<entity> _entities;
private readonly AutoMapper.IMapper _autoMapper;
private readonly Mapper _mapsterMapper;
public PerformanceTest()
{
var mocker = new AutoMocker();
_entities = Enumerable.Range(0, 1000000).Select(x => mocker.CreateInstance<entity>()).ToList();
var configuration = new AutoMapper.MapperConfiguration(cfg => cfg.AddProfile<AutoMapperProfile>());
_autoMapper = configuration.CreateMapper();
_mapsterMapper = new MapsterMapper.Mapper(new MapsterProfile());
}
[Benchmark]
public void Constructor()
{
var dtos = _entities.Select(x => new EntityDto
{
Id = x.Id,
Oid = x.Oid,
NickName = x.NickName,
Created = x.Created,
Enum = x.State,
EnumString = x.State.GetDescription(),
});
}
[Benchmark]
public void AutoMapper()
{
var dtos = _autoMapper.Map<ienumerable<entitydto>>(_entities);
}
[Benchmark]
public void Mapster()
{
var dtos = _mapsterMapper.Map<ienumerable<entitydto>>(_entities);
}
}
执行性能测试
var summary = BenchmarkRunner.Run<PerformanceTest>();
dotnet run --project .\ConsoleApp1.csproj -c Release
结果对比
通过使用 BenchmarkDotNet 来进行压测对比。从上图我们可以看出，使用 Constructor(直接创建对象) 的方式性能是最高的，然后就是 Mapster，最后才是 AutoMapper。
使用 ReadableExpressions.Visualizers 查看 Execution Plan
在项目中一直在使用 AutoMapper 来做对象转换，看 Github 活跃度，按理说不应该出现这么明显的性能问题。好奇心驱使我项研究一下，通过和作者沟通后了解到，'AutoMapper' 本身会有一个所谓的执行计划 execution plan，可以通过安装插件 ReadableExpressions.Visualizers 来查看。
在 AutoMapper 的配置地方添加如下代码：
var executionPlan = configuration.BuildExecutionPlan(typeof(Entity), typeof(EntityDto));
var executionPlanStr = executionPlan.ToReadableString();
查看 executionPlanStr 值，如下所示：
(src, dest, ctxt) =>
{
EntityDto typeMapDestination;
return (src == null)
? null
: {
typeMapDestination = dest ?? new EntityDto();
try
{
var resolvedValue =
{
try
{
Entity src;
return (((src = src) == null) || false) ? default(int) : src.Id;
}
catch (NullReferenceException)
{
return default(int);
}
catch (ArgumentNullException)
{
return default(int);
}
};
typeMapDestination.Id = resolvedValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
try
{
var resolvedValue =
{
try
{
Entity src;
return (((src = src) == null) || false) ? default(Guid) : src.Oid;
}
catch (NullReferenceException)
{
return default(Guid);
}
catch (ArgumentNullException)
{
return default(Guid);
}
};
typeMapDestination.Oid = resolvedValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
try
{
var resolvedValue =
{
try
{
Entity src;
return (((src = src) == null) || false) ? null : src.NickName;
}
catch (NullReferenceException)
{
return null;
}
catch (ArgumentNullException)
{
return null;
}
};
var propertyValue = (resolvedValue == null) ? null : resolvedValue;
typeMapDestination.NickName = propertyValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
try
{
var resolvedValue =
{
try
{
Entity src;
return (((src = src) == null) || false) ? default(bool) : src.Created;
}
catch (NullReferenceException)
{
return default(bool);
}
catch (ArgumentNullException)
{
return default(bool);
}
};
typeMapDestination.Created = resolvedValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
try
{
var resolvedValue =
{
try
{
Entity src;
return (((src = src) == null) || false) ? default(MyEnum) : src.State;
}
catch (NullReferenceException)
{
return default(MyEnum);
}
catch (ArgumentNullException)
{
return default(MyEnum);
}
};
typeMapDestination.Enum = resolvedValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
try
{
var resolvedValue =
{
try
{
return ((Enum)src.State).GetDescription();
}
catch (NullReferenceException)
{
return null;
}
catch (ArgumentNullException)
{
return null;
}
};
var propertyValue = (resolvedValue == null) ? null : resolvedValue;
typeMapDestination.EnumString = propertyValue;
}
catch (Exception ex)
{
return throw new AutoMapperMappingException(
"Error mapping types.",
ex,
AutoMapper.TypePair,
TypeMap,
PropertyMap);
}
return typeMapDestination;
};
}
使用 dotTrace 进行性能跟踪
通过使用 JetBrains dotTrace 来查看程序执行情况，如下图所示：
从图中我们可以看到，GetDescription 方法性能占用高达 8.38%。我尝试将这个枚举转字符串的扩展方法每次都返回固定值，如下所示：
public static class Extension
{
public static string GetDescription(this Enum value)
{
return "aaa";
//var field = value.GetType().GetField(value.ToString());
//if (field == null) return "";
//return Attribute.GetCustomAttribute(field,
// typeof(DescriptionAttribute)) is not DescriptionAttribute attribute
// ? value.ToString()
// : attribute.Description;
}
}
再次进行性能测试，发现 AutoMapper 的性能提升了不少。
但是，由于本身性能基数比较大，所有依然存在性能问题
