Multi-processor/Vista/Processor Affinity settings

[AtW]

I use it in .NET, there is a Win32 call that sets it: this can reduce amount of CPU switching if you have heavily multi threaded app that really uses a lot of CPU (perfmon can show number of switches).

Generally speaking you won't gain much - on multi-core CPUs if you are not loading all cores, then system will switch from one core to another thus avoiding one core being hot when others ain't.

[Sysman]

Given that the affinity may be set, has anyone noticed any real performance gains using the setting?

I had a 2 CPU system back when NT 4.0 first came out. Not many apps came with multithreaded capability in those days, but I did achieve performance gains by using Task Manager to set the affinity of my main comms program to processor 1.

I managed to find an API to change affinity of the current process, but didn't work out how to change the affinity of another process (a contract overseas took precedence). Starting with DP's example, this is your challenge.

I didn't have the sources to that comms program, so would simply fire it up in the morning, change affinity via Task Manager, and the job was done. The comms program suffered from its DOS/Win 3.1 heritage by polling constantly, thus sucking up as much CPU as was available. Hence the performance gain was pretty much assured - YMMV.

[DimPrawn]

I think this might help

http://blogs.techrepublic.com.com/pr...lopment/?p=691

[Churchill]

Three questions.

Ok, there is the option to set processor affinity by means of the Windows Task Manager. Is there another way that this may be set automatically for a given application?

Given that the affinity may be set, has anyone noticed any real performance gains using the setting?

What's the optimum configuration say for Internet Explorer given that (my assumption) the low-level comms handling will be performed at the operating system level on processor "0"...?

Any comments particularly about my assumptions gratefully received.

Cheers,

Churchill.