What you need to know about performance in Entity Framework

http://msdn.microsoft.com/en-us/data/hh949853.aspx 

Mapping Views
Mapping views are set of SQL statements that represents the database in an abstract way, which are also part of the metadata.
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Query execution
Deferred vs. Immediate execution
Client side execution of LINQ queries
Query and mapping complexity
Mapping complexity
Query complexity
Relationships
Query paths
Saving changes
Distributed Transactions

Strategies for Performance improvement

Pre-generate views
Consider using NoTracking merge option for queries
Return the correct amount of data
Limit the scope of ObjectContext
Consider opening db connection manually.

Extra

• In EF its best to understand how query execution happens 
• Data Source is the one which provides connection pooling facility. Not the Entity Framework. The .NET provider for SQL Server provides support for Connection Pooling
• In previous versions of EF (before 6) there was a performance problem when using Contains. This has been fixed now.
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https://msdn.microsoft.com/en-us/data/hh949853.aspx
http://www.asp.net/web-forms/overview/older-versions-getting-started/continuing-with-ef/maximizing-performance-with-the-entity-framework-in-an-asp-net-web-application

http://msdn.microsoft.com/en-us/library/8xx3tyca(v=vs.110).aspx

http://stackoverflow.com/questions/3653009/entity-framework-and-connection-pooling?rq=1

http://www.asp.net/whitepapers/aspnet-data-access-content-map#gettingstarted

http://msdn.microsoft.com/en-us/library/cc853327.aspx