Summary: | SMP code requires 2+ processors? | ||
---|---|---|---|
Product: | Gentoo Linux | Reporter: | Ed Grimm <paranoid> |
Component: | [OLD] Core system | Assignee: | x86-kernel (DEPRECATED) <x86-kernel> |
Status: | RESOLVED INVALID | ||
Severity: | blocker | ||
Priority: | Lowest | ||
Version: | unspecified | ||
Hardware: | All | ||
OS: | All | ||
Whiteboard: | |||
Package list: | Runtime testing required: | --- |
Description
Ed Grimm
2004-02-21 19:14:23 UTC
Could you possibly give an example as to which SMP code might be beneficial to UP boxes? SMP machines do things in a manner that requires a whole new method of thinking over the uniprocessor machines. The busses and local, as opposed to global, spinlocks are the main culprits here. With one processor, you don't really have to worry about the interrupt controllers. With multiple processors, when the interrupt is raised, the importance of the interrupt, and which processor it is assigned to are all taken into affect. I'm jut having trouble visualizing which bits of code could help uniprocessor machines. This is a kernel config question, not a gentoo-kernel issue, as the gentoo-kernel does not patch this code at all. Also, if you enable CONFIG_PREEMPT, and run a UP kernel, all of the SMP code is still present (spinlocks, etc.) And by definition, the NUM_CPUS can not be less than 2 for a SMP kernel. The fact that you can choose this at all is a memory savings only (if you select less than the default 32 you save some space in kernel memory for some variable types.) So in short, this is not a bug at all. |