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Date: Fri, 7 Feb 2014 11:49:57 -0600 (CST)
From: Christoph Lameter <cl@linux.com>
To: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [RFC PATCH 3/3] slub: fallback to get_numa_mem() node if we want
 to allocate on memoryless node
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On Fri, 7 Feb 2014, Joonsoo Kim wrote:

> > This check wouild need to be something that checks for other contigencies
> > in the page allocator as well. A simple solution would be to actually run
> > a GFP_THIS_NODE alloc to see if you can grab a page from the proper node.
> > If that fails then fallback. See how fallback_alloc() does it in slab.
> >
>
> Hello, Christoph.
>
> This !node_present_pages() ensure that allocation on this node cannot succeed.
> So we can directly use numa_mem_id() here.

Yes of course we can use numa_mem_id().

But the check is only for not having any memory at all on a node. There
are other reason for allocations to fail on a certain node. The node could
have memory that cannot be reclaimed, all dirty, beyond certain
thresholds, not in the current set of allowed nodes etc etc.