Re: [PATCH] reduce inter-node balancing frequency

[Nick Piggin <nickpiggin@yahoo.com.au>]

Jesse Barnes wrote:
> On Thursday, July 15, 2004 8:14 pm, Martin J. Bligh wrote:
> 
>>>Nick, we've had this patch floating around for awhile now and I'm
>>>wondering what you think.  It's needed to boot systems with lots (e.g.
>>>256) nodes, but could probably be done another way.  Do you think we
>>>should create a scheduler domain for every 64 nodes or something?
>>
>>I think that'd make a lot of sense ...
> 
> 
> Yeah, though a smaller number of nodes would probably make more sense :)
> 

Thirded :)

> 
>>>Any other NUMA folks have thoughts about these values?
>>
>>Yeah, change them in arch specific code, not in the global stuff ;-)
> 
> 
> What, you mean we're the only ones with 256 nodes?
> 

Yeah, these numbers actually used to be a lot higher, but someone
at Intel (I forget who it was right now) found them to be too high
on even a 32 way SMT system. They could probably be raised a *little*
bit in the generic code.

> 
>>But seeing as they're dependant (for you) on machine size, as well as
>>arch type, you probably need to do something cleverer in
>>arch_init_sched_domain
> 
> 
> Ok, I'll check that out.
> 
> 
>>But the big bugaboo is arch-specific vs general ... we need to break
>>opteron vs i386 vs ia64 out from each other ... they all need different
>>coefficients.
>>
>>If you were going to be really fancy, we could do it in common code off
>>the topology stuff ... but for now, I think it's easier to just set 'em
>>per arch ...
> 
> 
> We may have enough information to do that already... I'll look.
> 

The plan is to allow arch overridable SD_CPU/NODE_INIT macros for
those architectures that just look like a regular SMT+SMP+NUMA, and
have the generic code set them up.