Re: [RFC 1/2] slub: Avoid trying to allocate memory on offline nodes

[Christopher Lameter <cl@linux.com>]

On Wed, 1 Aug 2018, Jeremy Linton wrote:

> diff --git a/mm/slub.c b/mm/slub.c
> index 51258eff4178..e03719bac1e2 100644
> --- a/mm/slub.c
> +++ b/mm/slub.c
> @@ -2519,6 +2519,8 @@ static void *___slab_alloc(struct kmem_cache *s, gfp_t gfpflags, int node,
>  		if (unlikely(!node_match(page, searchnode))) {
>  			stat(s, ALLOC_NODE_MISMATCH);
>  			deactivate_slab(s, page, c->freelist, c);
> +			if (!node_online(searchnode))
> +				node = NUMA_NO_NODE;
>  			goto new_slab;
>  		}
>  	}
>

Would it not be better to implement this check in the page allocator?
There is also the issue of how to fallback to the nearest node.

NUMA_NO_NODE should fallback to the current memory allocation policy but
it seems by inserting it here you would end up just with the default node
for the processor.