问题
I noticed that building in dotnet core 2 seemed a lot slower.
But the timing after the build always showed 'only' 15 seconds.
I couldn't believe that so I timed it with time.
> time dotnet build
Microsoft (R) Build Engine version 15.3.409.57025 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.
hrm -> /Users/r/dev/hrm/bin/Debug/netcoreapp2.0/hrm.dll
Build succeeded.
0 Warning(s)
0 Error(s)
Time Elapsed 00:00:15.45
real 0m52.366s
user 0m36.851s
sys 0m15.458s
That seemed more correct. Almost a minute.
I then tried without restore and it was a lot faster:
> time dotnet build --no-restore
Microsoft (R) Build Engine version 15.3.409.57025 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.
hrm -> /Users/r/dev/hrm/bin/Debug/netcoreapp2.0/hrm.dll
Build succeeded.
0 Warning(s)
0 Error(s)
Time Elapsed 00:00:15.39
real 0m15.795s
user 0m11.397s
sys 0m4.238s
But dotnet also shows 15 seconds.
Could it be that only building is counted in the timings?
Not sure why a restore is always slow when everything is already restored.
Are there other ways I could speed up the building process? Disable telemetry? (I'm using osx, my environment is set to development)
I prefer to use dotnet watch run but that seems even slower.
Running dotnet watch to view the parameters is taking 12 seconds.
> time dotnet watch
Microsoft DotNet File Watcher 2.0.0-rtm-26452
Usage: dotnet watch [options] [[--] <arg>...]
Options:
....
real 0m12.631s
user 0m8.880s
sys 0m3.816s
Is this only on my system?
Update:
Here is the result from dotnet restore /clp:PerformanceSummary
> dotnet restore /clp:PerformanceSummary
Restore completed in 43.95 ms for /Users/roeland/dev/hrm/hrm.csproj.
Restore completed in 52.73 ms for /Users/roeland/dev/hrm/hrm.csproj.
Restore completed in 38.48 ms for /Users/roeland/dev/hrm/hrm.csproj.
Project Evaluation Performance Summary:
36252 ms /Users/roeland/dev/hrm/hrm.csproj 3 calls
Project Performance Summary:
36424 ms /Users/roeland/dev/hrm/hrm.csproj 9 calls
24359 ms Restore 1 calls
1 ms _IsProjectRestoreSupported 2 calls
12011 ms _GenerateRestoreProjectPathWalk 1 calls
1 ms _GenerateRestoreProjectPathItemsPerFramework 1 calls
43 ms _GenerateRestoreGraphProjectEntry 1 calls
0 ms _GetRestoreSettingsPerFramework 1 calls
6 ms _GenerateProjectRestoreGraph 1 calls
3 ms _GenerateProjectRestoreGraphPerFramework 1 calls
Target Performance Summary:
0 ms _GenerateRestoreGraphProjectEntry 1 calls
0 ms _GenerateProjectRestoreGraph 1 calls
0 ms _GetRestoreTargetFrameworksAsItems 1 calls
0 ms _GetRestoreProjectStyle 2 calls
0 ms CheckForImplicitPackageReferenceOverridesBeforeRestore 2 calls
0 ms _CheckForUnsupportedNETCoreVersion 1 calls
0 ms _IsProjectRestoreSupported 1 calls
0 ms _GetRestoreSettingsPerFramework 1 calls
0 ms _GetProjectJsonPath 2 calls
0 ms _GetRestoreSettingsOverrides 1 calls
1 ms _GenerateRestoreProjectPathWalk 1 calls
1 ms _GenerateRestoreProjectPathItemsPerFramework 1 calls
1 ms _GenerateRestoreSpecs 1 calls
1 ms _GenerateRestoreProjectSpec 1 calls
2 ms _GenerateProjectRestoreGraphPerFramework 1 calls
2 ms _GetRestoreTargetFrameworksOutput 1 calls
5 ms _GenerateRestoreDependencies 1 calls
10 ms _LoadRestoreGraphEntryPoints 1 calls
20 ms _GenerateDotnetCliToolReferenceSpecs 1 calls
21 ms _GetRestoreSettings 1 calls
54 ms _GenerateRestoreGraph 1 calls
216 ms Restore 1 calls
12007 ms _GenerateRestoreProjectPathItems 1 calls
12014 ms _GetAllRestoreProjectPathItems 1 calls
12058 ms _FilterRestoreGraphProjectInputItems 1 calls
Task Performance Summary:
1 ms Message 3 calls
1 ms ConvertToAbsolutePath 2 calls
1 ms GetRestorePackageReferencesTask 1 calls
1 ms GetRestoreProjectReferencesTask 1 calls
2 ms GetRestoreProjectFrameworks 1 calls
3 ms RemoveDuplicates 5 calls
4 ms WarnForInvalidProjectsTask 1 calls
18 ms GetRestoreSettingsTask 1 calls
20 ms GetRestoreDotnetCliToolsTask 1 calls
216 ms RestoreTask 1 calls
36121 ms MsBuild 9 calls
回答1:
Long story short: MSBuild scans the entire folder structure based on glob patterns defined by the SDK used. This is done for each project evaluation and the NuGet restore seems to trigger at least three full evaluations.
Since it is slow to scan large directories, the SDKs define globbing patterns used to exclude some known large directories that are usually not wanted as part of the project anyway (node_modules, bower_components etc.).
It has been known that special circumstances may circumvent these optimisations and or even trigger performance bugs in the include/exclude glob pattern expansion / matching.
As a precaution, add all folders known to be excluded to the DefaultItemExcludes property (inside of a <PropertyGroup> element):
<DefaultItemExcludes>custom\node_modules\**;$(DefaultItemExcludes)</DefaultItemExcludes>
回答2:
For me excluding.git folder helped to make build around 10x faster.
<PropertyGroup>
<DefaultItemExcludes>.git\**;$(DefaultItemExcludes)</DefaultItemExcludes>
</PropertyGroup>
来源：https://stackoverflow.com/questions/45763755/dotnet-core-2-long-build-time-because-of-long-restore-time