We are running an HP ProLiant Windows Server 2008 R2 SP1 and IIS 7.5 on a dual CPU Xeon system (16 cores per CPU). The web site is a ASP.NET 4.5 running in a App-pool using a a classic managed pipeline.

When I load test our application only one CPU is loaded. The other stays CPU flat, i.e. it is using 16 cores of available 32.

I checked the Affinity option in the app pool settings in IIS and it is False.

I then checked the Affinity for the w3wp.exe process in the Task Manager and it displayed two processor groups: "Group 0" and "Group 1".

All cores were checked in "Group 0" but none in "Group 1". When I tried selecting all in "Group 1" the setting wouldn't save (it just opened up unselected when I checked "Set affinity ..." again.)

Is IIS able to handle dual processors for a single app pool? Is there a missing setting I need to set? Any ideas?

  • It's not clear to me if it's using 1 core out of the 32 possible, or using 1 CPU (16 cores). Please edit your question to clarify.
    – Joel Coel
    Feb 22 '16 at 17:38
  • 1 CPU, 16 cores. The other CPU lies almost dormant (handling other processes it seems)
    – Karlth
    Feb 22 '16 at 21:26
  • What CPUs does the server have? Are you sure it's not using all physical cores and just not using multiple virtual cores that share a physical core? Feb 22 '16 at 22:35
  • @DavidSchwartz Yes. See answer below.
    – Karlth
    Feb 22 '16 at 23:05

This seems to be a known issue with ProLiant servers and HP has issued a BIOS patch to address it:


It worked.

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