Re: NUMA mempolicy /proc code in mainline shouldn't have been merged

[Christoph Lameter]

On Mon, 19 Sep 2005, Andi Kleen wrote:

> On Mon, Sep 19, 2005 at 10:11:20AM -0700, Christoph Lameter wrote:
> > However, one still does not know which memory section (vma) is allocated 
> > on which nodes. And this may be important since critical data may need to 
> 
> Maybe. Well sure of things could be maybe important. Or maybe not.
> Doesn't seem like a particularly strong case to add a lot of ugly
> code though.

We gradually need to fix the deficiencies of the policy layer. Calling 
fixes "ugly code" and refusing to discuss solutions does not help anyone.

> > External memory policy management is a necessary feature for system 
> > administration, batch process scheduling as well as for testing and 
> > debugging a system.
> 
> I'm not convinced of this at all. Most of these things proposed so far
> can be done much simpler with 90% of the functionality (e.g. just swapoff
> per process for migration) , and I haven't seen a clear rationale except
> for lots of maybes that the missing 10% are worth all the complexity
> you seem to plan to add.

Have you ever had the challenge to work with large HPC applications on a 
large NUMA system? Which things? Many HPC apps do not use swap space 
at all and we likely wont be using swap for page migration (see Marcelo's 
work on a migration cache). All I have heard is you imagining complex 
solutions ("performance counters" etc) to things that would be simple if 
the policy layer would be up to the task.
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