lkml.org 
[lkml]   [2014]   [Apr]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 0/5] Use an alternative to _PAGE_PROTNONE for _PAGE_NUMA v2

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Apr 08, 2014 at 05:46:52PM +0100, Mel Gorman wrote:
> > Someone will ask why automatic NUMA balancing hints do not use "real"
> > PROT_NONE but as it would need VMA information to do that on all
> > architectures it would mean that VMA-fixups would be required when marking
> > PTEs for NUMA hinting faults so would be expensive.
>
> Like this:
>
> https://lkml.org/lkml/2012/11/13/431
>
> That used the generic PROT_NONE infrastructure and compared, on fault,
> the page protection bits against the vma->vm_page_prot bits?
>
> So the objection to that approach was the vma-> dereference in
> pte_numa() ?

I think the real underlying objection was that PTE_NUMA was the last
leftover from AutoNUMA, and removing it would have made it not a
'compromise' patch set between 'AutoNUMA' and 'sched/numa', but would
have made the sched/numa approach 'win' by and large.

The whole 'losing face' annoyance that plagues all of us (me
included).

I didn't feel it was important to the general logic of adding access
pattern aware NUMA placement logic to the scheduler, and I obviously
could not ignore the NAKs from various mm folks insisting on PTE_NUMA,
so I conceded that point and Mel built on that approach as well.

Nice it's being cleaned up, and I'm pretty happy about how NUMA
balancing ended up looking like.

Thanks,

Ingo


\
 
 \ /
  Last update: 2014-04-09 08:41    [W:0.685 / U:0.332 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site