Experience using gcServer="true" to set garbage collector for .NET

Question

Has someone used a configuration enabling the garbage collector optimized for multi-processor machines using Aspnet.config with :

<gcServer enabled="true"/> <gcConcurrent enabled="true"/> 

Was there an improvement in the performance of your site?
Are any problems noticed?

Answer 1

First, Concurrent and Server are mutually exclusive options. See this blog post for some details on server GC misconceptions. However, ASP.NET, by default, hosts the server GC (see Scott Hanselman's discussion), so there will be no difference there.

I'd recommend sticking with server instead of concurrent for an ASP.NET website. For a user-mode application, the concurrent GC has been user responsiveness, since the server gc will cause "hangs".

I have used the server GC, and noticed significant improvements in certain situations.

The server mode GC does help user apps, though, if you're user application is working with huge memory pools, and getting highly fragmented.

Answer 2

(very old question, I know, but I thought to add this anyway)

There's one major difference between Server GC and Concurrent GC: the Server GC has one thread per processor and suspends the threads on that processor when doing a collection, the server Concurrent GC thread runs in parallel with the other threads, i.e., no suspension. See this MSDN article for more info and more subtle differences.

Depending on the time a cycle takes, this can make a rather big difference in user responsiveness of your application, so choose wisely. In case of ASP.NET, which does not have a UI, Server GC is the better (and default) option.