Re: [PATCH] reduce inter-node balancing frequency

["Martin J. Bligh" <mbligh@aracnet.com>]

--Jesse Barnes <jbarnes@engr.sgi.com> wrote (on Thursday, July 15, 2004 21:58:17 -0400):

> On Thursday, July 15, 2004 9:48 pm, Nick Piggin wrote:
>> 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.
> 
> Ok, but I wouldn't want to hurt the performance of small machines at all.  If 
> possible, I'd rather just add another level to the hierarchy if MAX_NUMNODES 
>> some value.

Arch code. Arch code. Arch code ;-) Or at least base it of nr_cpus or 
numnodes. Seriously ... a 2x or 4x opteron obviously needs different
parameters from a 16x x440 or a 512x SGI box ... why we have a flexible
infrastructure that can stand on its head and do backflips, and then
we don't use it at all is a mystery to me ;-)

I'd even go so far as to suggest there should be NO default settings for
NUMA, only in arch code - that'd make people actually think about it.
If there are, they should be based off the topo infrastructure, not static
values.
 
>> > 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.
> 
> Would simply creating a 'supernode' scheduling domain work with the existing 
> scheduler?  My thought was that in the ia64 code we'd create them for every N 
> regular nodes; its children would be the regular nodes with the existing 
> defaults.

Nick would know better than I, but I think so ... it seems to cope with
arbitrary levels, groupings, ... gravitational dimensions, etc ;-)

M.