"Maximum number of CPUs" option when compiling kernel

prejudged_fire · 08-24-2008, 02:22 PM

Does that option refer to the maximum number of physical CPUs the kernel will support, or the number of cores it will support?

syg00 · 08-24-2008, 05:29 PM

yes ...

Haven't looked at the code for this but I'd be guessing the number of "entities" that processes can be possibly dispatched on. I always make sure it's more than I reckon I'll need.

prejudged_fire · 08-24-2008, 06:08 PM

Quote:

Originally Posted by syg00

yes ...

Haven't looked at the code for this but I'd be guessing the number of "entities" that processes can be possibly dispatched on. I always make sure it's more than I reckon I'll need.

So it's the number of cores then? If so, I was going to set it to 4. I have a dual core CPU, but I could always get a Quad later. But if it's the physical processors, I'd only set it to 2, of course.

syg00 · 08-24-2008, 08:10 PM

There is no (very minor) benefit in setting it to the actual number of processors. I use 8 for everything, unless I need more. Scheduler queues get built for each processor on each (NUMA) node found - they're not built for all the processors you set as the limit. I think that's right, but I haven't actually checked the "early" code.
FWIW Core 2 quad shows up as 4 processors.

prejudged_fire · 08-28-2008, 06:56 PM

Ok, thank you for the information