Constant SQL Server 80% CPU Utilization

We have a small (for now) Asp.Net MVC 5 website on a dedicated VPS. When I go to the server and fire-up task manager, I see that "SQL Server Windows NT - 64 bit" is using around 80% of CPU and 170MB of RAM and IIS is using 6% CPU and 400MB of RAM. Server Specs are:

CPU 1.90Ghz dual core
Memory 2GB
Windows Server 2012
SQL Server Express 2012
Disk Space: 25GB, 2.35 Free.

The database is not very big. Its backup is less than 10MB.

I have tried to optimize the website as much as I could. I added caching to a lot of controllers and implemented donut caching for quite a lot of controllers. But today, even though there were only 5 users online, our search wouldn't work. I restarted the Windows on the server and it started working but I got the high CPU usage the minute server started. Interestingly when I open the SQL Server Management Studio and try to get the report for top CPU-consuming queries it says that there are no queries currently consuming any CPU!!! But at the same time I can see that SQL server is consuming a lot of CPU. How can I examine what is taking all the CPU? Below is a picture from the server:

I was/am very careful with designing and implementing the website. All the database access is through latest version of Entity Framework. I just wonder if the server's specs are low. Any help would be very much appreciated.

Update:

Here's the result of the sp_who2 stored procedure.

回答1:

I would agree running SQL Profiler to spot large query durations and large write operations. Try running perfmon and spotting any potential connection leaks (reclaimed connections).

回答2:

This could happen if the memory set to use is more than the available memory on the box. The default memory setting of 2147483647MB. In our case the AWS box had only 30.5 GB so we changed the setting to 26GB and the CPU usage fell to 40%. You generally want to leave 20% of memory for OS and its operations.