Re: [NUMA] Display and modify the memory policy of a process through /proc/<pid>/numa_policy

[Christoph Lameter <clameter@engr.sgi.com>]

On Fri, 15 Jul 2005, Andi Kleen wrote:

> So for what does that batch monstrosity need to know 
> about the VMAs? 

It needs to know where the memory of a process is. Thus 
/proc/<pid>/numa_maps.

> I don't believe any admin will mess with virtual addresses.

No but they will mess with vma's which are only identifiable by the 
starting virtual address.
 
> But for "uncooperative" programs working on bigger objects
> like threads/files/shm areas/processes makes much more sense. And gives
> much cleaner interfaces too.

Look at the existing patches and you see a huge complexity and heuristics 
because the kernel guesses which vma's to migrate. If the vma are 
exposed to the batch scheduler / admin then things become much easier to 
implement and the batch scheduler / admin has finer grained control.

> Now I can see some people being interested in more fine grained
> policy, but the only sane way to do that is to change the source
> code and use libnuma.

Can libnuma change the memory policy and move pages of existing processes?
 
> Basically to mess with finegrained virtual addresses you need code access,
> and when you have that you can as well do it well and add 
> libnuma and recompile.

libnuma is pretty heavy and AFAIK does not have the functionality that is 
required here.
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