Search code examples
asp.netperformanceentity-framework-5dbcontextintellitrace

Why is DbContext.SaveChanges 10x slower in debug mode

Can somebody explain

  1. Why does DbContext.SaveChanges run ~10x slower in debug mode than production mode?
  2. Is there any way I can speed this up?

In debug mode, my webpage takes 116 seconds to load versus 15 seconds if I start the project without debugging.

I have set trace statements and identified that ~100 of the 116 seconds is spent in my DbContext.SaveChanges method when in debug mode.

Running the project without debugging only 7 seconds in spent in the same section.

Let me know in the comments if you'd like more information..

Project Setup:

  • ASP.NET webpage
  • VS2012
  • SQLServer2012
  • Entity Framework 5.0

Additional Info: (Let me know in the comments if you need more)

  • The cumulative number of sql queries over the SaveChanges method is 20,000
  • Production Connection String: Data Source=PC-DEV;Initial Catalog=aspnet-2013-06-04;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFrameworkMUE
  • Debug Connection String: Data Source=PC-DEV;Initial Catalog=aspnet-2013-06-04;Integrated Security=True;MultipleActiveResultSets=True;Application Name=EntityFrameworkMUE
  • I've also experienced the same relative performance with LocalDB as the backing database

Update:

As @ruionwriting suggested, I profiled the database and what I found is that the ~20,000 sql commands take exactly the same time whether the project is run in debug or production mode. ( 0 ms per command).

However, the absolute time difference on average between the 20,000 commands is 5ms in debug mode.

Contrasted with production mode, the average time difference over the set of commands is 0.3 ms.

This is the approximate 10x time performance difference and isolates entity framework as what is taking the extra time in debug mode.

Is there a way to configure the debug build such that EntityFramework can be referenced without debugging flags?

And if I were to somehow achieve the performance back through some compiler magic, what would I lose in terms of debugging capabilities? Currently I can't step into entity framework code so I don't think I would miss anything.

Thanks!

Solution

  • Whohoo!

    Ok, so the reason debug mode was exceptionally slow was because Visual Studio's Intellitrace was recording each ADO.NET event ( all 20, 000 of them ) generated by Entity Framework.

    So Tools-> Options -> IntelliTrace and Uncheck "Enable IntelliTrace" fixed the issue.

    Or one can also just filter out the ADO.NET events by going to Tools->Options -> IntelliTrace -> IntelliTrace Events and uncheck ADO.NET

    Thanks for everyone's suggestions.

    A section here talks about Will Intellitrace slow down my app

    How to Filter IntelliTrace Events