Regression in single context creation perf

[ajcvickers]

[smitpatel]

Suspected commit according to meeting https://github.com/dotnet/efcore/pull/19517/files

Does initializing context also initializes DbSets even if not used?

[AndriySvyryd]

@smitpatel That's pretty much the only thing that happens before a context is used https://github.com/dotnet/efcore/blob/master/src/EFCore/DbContext.cs#L112

[AndriySvyryd]

And if we can confirm that #19517 caused it we don't have or really can fix it

[roji]

Should be really easy to simply run the benchmark on the cmdline on both commits to check (let me know if you run into trouble).

[smitpatel]

Seems like @roji is volunteering to verify the commit for regression.

[roji]

That was not quite the semantic content of my message... however:

Before change (f98509f)

BenchmarkDotNet=v0.11.3, OS=ubuntu 19.10
Intel Xeon W-2133 CPU 3.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET Core SDK=3.1.100
  [Host] : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), 64bit RyuJIT

Toolchain=InProcessToolchain  

Method	Mean	Error	StdDev	Gen 0/1k Op	Gen 1/1k Op	Gen 2/1k Op	Allocated Memory/Op
CreateAndDisposeUnusedContext	142.0 ms	1.142 ms	1.068 ms	34250.0000	-	-	141.75 MB

After change (dd843a2)

BenchmarkDotNet=v0.11.3, OS=ubuntu 19.10
Intel Xeon W-2133 CPU 3.60GHz, 1 CPU, 12 logical and 6 physical cores
.NET Core SDK=3.1.100
  [Host] : .NET Core 3.1.1 (CoreCLR 4.700.19.60701, CoreFX 4.700.19.60801), 64bit RyuJIT

Toolchain=InProcessToolchain  

Method	Mean	Error	StdDev	Median	Gen 0/1k Op	Gen 1/1k Op	Gen 2/1k Op	Allocated Memory/Op
CreateAndDisposeUnusedContext	193.7 ms	3.860 ms	9.825 ms	188.1 ms	38000.0000	-	-	158.54 MB

---

For reference, running is super simple has no hard dependency on @roji:

• cd benchmark/EFCore.Sqlite.Benchmarks (invert slashes if on exotic operating systems)
• dotnet run -c Release -f netcoreapp3.1 -- --filter "*CreateAndDisposeUnusedContext*" --inProcess

[smitpatel]

That was not quite the semantic content of my message... however:

Oops! My mistake! 😉

[ajcvickers]

I have ideas.