Messages in this thread | | | Date | Wed, 03 Sep 2003 14:46:06 -0700 | From | "Martin J. Bligh" <> | Subject | Re: Scaling noise |
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>> That's where I disagree - it's much easier for the USER because an SSI >> cluster works out all the load balancing shit for itself, instead of >> pushing the problem out to userspace. It's much harder for the KERNEL >> programmer, sure ... but we're smart ;-) And I'd rather solve it once, >> properly, in the right place where all the right data is about all >> the apps running on the system, and the data about the machine hardware. > > This is only truly feasible when the nodes are homogeneous. They will > not be as there will be physical locality (esp. bits like device > proximity) concerns.
Same problem as a traditonal set up of a NUMA system - the scheduler needs to try to move the process closer to the resources it's using.
> It's vaguely possible some kind of punting out > of the kernel of the solutions to these concerns is possible, but upon > the assumption it will appear, we descend further toward science fiction.
Nah, punting to userspace is crap - they have no more ability to solve this than we do on any sort of dynamic worseload, and in most cases, much worse - they don't have the information that the kernel has available, at least not on a timely basis. The scheduler belongs in the kernel, where it can balance decisions across all of userspace, and we have all the info we need rapidly and efficiently available.
> Some of these proposals also beg the question of "who's going to write > the rest of the hypervisor supporting this stuff?", which is ominous.
Yeah, it needs lots of hard work by bright people. It's not easy.
M.
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