Question

I’ve come across a rather unique problem that I haven’t seen before.

The customer has a application server and a database server. The application server (win 2008) runs a ASP.NET MVC 3 App. The database server (also Win 2008) runs SQL Server 2008.

Whenever a request to the database is made, CPU for w3wp.exe goes up to 50 – 80 % and network traffic reaches 2% (of 10 Gbps). This takes a minute or so after which the requested web page is displayed.

I checked the actual Linq execution time and it only takes a few milliseconds to get the data.

I hope some of the professionals here can shed some light on what’s going on. Of course, it works on my machine.

update

Even a query executed from SQL Server Management Studio (on the app server) that retrieves 828 rows takes a full 12 seconds to complete… So I guess the problem is not the app but somewhere on the database server or the connection

update 2
Here’s something interesting I found out.

This is the slow code:

MyAppDataContext DataContext = MyAppDataContext.CreateNewContext();
IEnumerable<Requests> Entities = DataContext.Requests;

using (profiler.Step("get data")) {
    IEnumerable<Requests> dataset = from x in Entities
                                    where x.ControleStatus == 4
                                    orderby x.ID
                                    select x;
}

But when I change IEnumerable to IQueryable, the code executes 10x faster:

MyAppDataContext DataContext = MyAppDataContext.CreateNewContext();
IQueryable<Requests> Entities = DataContext.Requests.AsQueryable();

using (profiler.Step("get data")) {
    IQueryable<Requests> dataset = from x in Entities
                                   where x.ControleStatus == 4
                                   orderby x.ID
                                   select x;
}

So my question is: what could be causing this big difference between IEnumerable and IQueryable ?

Answer 1

Whenever a request to the database is made, CPU for w3wp.exe goes up
to 50 – 80 % and network traffic reaches 2% (of 10 Gbps).

1. Are you taking care of Memory leaks?
2. Using statements are included in the Database Interaction classes?
3. I use Red Gate ANTS Memory Profiler to check for the Memory Management Issues.
4. You are looking for SQL Profiler that tells Reads and Duration.