Slow incremental builds with .NET Core 2.0

Steps to reproduce

1. Build a solution
2. Build it again

Expected behavior

Building a project again should be fast if no files were changed. For example this happens in Visual Studio:

Restoring NuGet packages...
To prevent NuGet from restoring packages during build, open the Visual Studio Options dialog, click on the Package Manager node and uncheck 'Allow NuGet to download missing packages during build.'
1>------ Build started: Project: ScoreAnalyzer.Tests, Configuration: Debug Any CPU ------
1>ScoreAnalyzer.Tests -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.Tests\bin\Debug\netcoreapp2.0\ScoreAnalyzer.Tests.dll
========== Build: 1 succeeded, 0 failed, 8 up-to-date, 0 skipped ==========

Actual behavior

Rebuilding takes the same time as the first build.

C:\Users\Adam\Downloads\ScoreAnalyzer>dotnet build
Microsoft (R) Build Engine version 15.3.409.57025 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  ScoreAnalyzer.DTOs -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.DTOs\bin\Debug\netstandard2.0\ScoreAnalyzer.DTOs.dll
  Helpers -> C:\Users\Adam\Downloads\ScoreAnalyzer\Helpers\bin\Debug\netstandard2.0\Helpers.dll
  Utilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\Utilities\bin\Debug\netstandard2.0\Utilities.dll
  ScoreAnalyzer.AWS -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.AWS\bin\Debug\netstandard2.0\ScoreAnalyzer.AWS.dll
  MusicRepresentations -> C:\Users\Adam\Downloads\ScoreAnalyzer\MusicRepresentations\bin\Debug\netstandard2.0\MusicRepresentations.dll
  ScoreAnalyzer.TestUtilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.TestUtilities\bin\Debug\netstandard2.0\ScoreAnalyzer.TestUtilities.dll
  Evaluation -> C:\Users\Adam\Downloads\ScoreAnalyzer\Evaluation\bin\Debug\netstandard2.0\Evaluation.dll
  ScoreAnalyzer -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer\bin\Debug\netstandard2.0\ScoreAnalyzer.dll
  ScoreAnalyzer.Tests -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.Tests\bin\Debug\netcoreapp2.0\ScoreAnalyzer.Tests.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:12.22

C:\Users\Adam\Downloads\ScoreAnalyzer>dotnet build
Microsoft (R) Build Engine version 15.3.409.57025 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  ScoreAnalyzer.DTOs -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.DTOs\bin\Debug\netstandard2.0\ScoreAnalyzer.DTOs.dll
  Helpers -> C:\Users\Adam\Downloads\ScoreAnalyzer\Helpers\bin\Debug\netstandard2.0\Helpers.dll
  ScoreAnalyzer.AWS -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.AWS\bin\Debug\netstandard2.0\ScoreAnalyzer.AWS.dll
  Utilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\Utilities\bin\Debug\netstandard2.0\Utilities.dll
  MusicRepresentations -> C:\Users\Adam\Downloads\ScoreAnalyzer\MusicRepresentations\bin\Debug\netstandard2.0\MusicRepresentations.dll
  ScoreAnalyzer.TestUtilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.TestUtilities\bin\Debug\netstandard2.0\ScoreAnalyzer.TestUtilities.dll
  Evaluation -> C:\Users\Adam\Downloads\ScoreAnalyzer\Evaluation\bin\Debug\netstandard2.0\Evaluation.dll
  ScoreAnalyzer -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer\bin\Debug\netstandard2.0\ScoreAnalyzer.dll
  ScoreAnalyzer.Tests -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.Tests\bin\Debug\netcoreapp2.0\ScoreAnalyzer.Tests.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:05.57

C:\Users\Adam\Downloads\ScoreAnalyzer>dotnet build --no-restore
Microsoft (R) Build Engine version 15.3.409.57025 for .NET Core
Copyright (C) Microsoft Corporation. All rights reserved.

  ScoreAnalyzer.DTOs -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.DTOs\bin\Debug\netstandard2.0\ScoreAnalyzer.DTOs.dll
  Helpers -> C:\Users\Adam\Downloads\ScoreAnalyzer\Helpers\bin\Debug\netstandard2.0\Helpers.dll
  ScoreAnalyzer.AWS -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.AWS\bin\Debug\netstandard2.0\ScoreAnalyzer.AWS.dll
  Utilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\Utilities\bin\Debug\netstandard2.0\Utilities.dll
  ScoreAnalyzer.TestUtilities -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.TestUtilities\bin\Debug\netstandard2.0\ScoreAnalyzer.TestUtilities.dll
  MusicRepresentations -> C:\Users\Adam\Downloads\ScoreAnalyzer\MusicRepresentations\bin\Debug\netstandard2.0\MusicRepresentations.dll
  Evaluation -> C:\Users\Adam\Downloads\ScoreAnalyzer\Evaluation\bin\Debug\netstandard2.0\Evaluation.dll
  ScoreAnalyzer -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer\bin\Debug\netstandard2.0\ScoreAnalyzer.dll
  ScoreAnalyzer.Tests -> C:\Users\Adam\Downloads\ScoreAnalyzer\ScoreAnalyzer.Tests\bin\Debug\netcoreapp2.0\ScoreAnalyzer.Tests.dll

Build succeeded.
    0 Warning(s)
    0 Error(s)

Time Elapsed 00:00:05.36

Environment data

dotnet --info output:

.NET Command Line Tools (2.0.0)

Product Information:
 Version:            2.0.0
 Commit SHA-1 hash:  cdcd1928c9

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.15063
 OS Platform: Windows
 RID:         win10-x64
 Base Path:   C:\Program Files\dotnet\sdk\2.0.0\

Microsoft .NET Core Shared Framework Host

  Version  : 2.0.0
  Build    : e8b8861ac7faf042c87a5c2f9f2d04c98b69f28d

[nguerrera]

@zuckerthoben Sorry to hear that. Can you open a new issue so that we can iterate on that with you? Please start by sharing the output of dotnet build /clp:PerformanceSummary.

[axot]

Has same problem in OS X.