Re: [Lse-tech] [PATCH] cpusets - big numa cpu and memory placement

Matthew Dobson
2005-02-08T19:33:10Z

Nick Piggin wrote:
> Dinakar Guniguntala wrote:
>
>> On Mon, Feb 07, 2005 at 03:59:49PM -0800, Matthew Dobson wrote:
>>
>>
>>> Sorry to reply a long quiet thread, but I've been trading emails with
>>> Paul Jackson on this subject recently, and I've been unable to
>>> convince either him or myself that merging CPUSETs and CKRM is as
>>> easy as I once believed. I'm still convinced the CPU side is doable,
>>> but I haven't managed as much success with the memory binding side of
>>> CPUSETs. In light of this, I'd like to remove my previous objections
>>> to CPUSETs moving forward. If others still have things they want
>>> discussed before CPUSETs moves into mainline, that's fine, but it
>>> seems to me that CPUSETs offer legitimate functionality and that the
>>> code has certainly "done its time" in -mm to convince me it's stable
>>> and usable.
>>>
>>> -Matt
>>>
>>
>>
>> What about your proposed sched domain changes?
>> Cant sched domains be used handle the CPU groupings and the
>> existing code in cpusets that handle memory continue as is?
>> Weren't sched somains supposed to give the scheduler better knowledge
>> of the CPU groupings afterall ?
>>
>
> sched domains can provide non overlapping top level partitions.
> It would basically just stop the multiprocessor balancing from
> moving tasks between these partitions (they would be manually
> moved by setting explicit cpu affinities).

Yep. That's the idea! :)

> I didn't really follow where that idea went, but I think at least
> a few people thought that sort of functionality wasn't nearly
> fancy enough! :)

Well, that's about how far the idea was supposed to go. ;) I think named
hierarchical sched_domains would offer the same functionality (at least for CPU
partitioning) as CPUSETs. I'm not sure who didn't think it was fancy enough,
but if you or anyone else can describe CPUSETs configurations that couldn't be
represented by sched_domains trees, I'd be very curious to hear about them.

-Matt