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SubjectRe: [PATCH] [1/4] SLAB: Handle node-not-up case in fallback_alloc()
On Wed, 3 Feb 2010, Andi Kleen wrote:

> When fallback_alloc() runs the node of the CPU might not be initialized yet.
> Handle this case by allocating in another node.
>

That other node must be allowed by current's cpuset, otherwise
kmem_getpages() will fail when get_page_from_freelist() iterates only over
unallowed nodes.

> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> ---
> mm/slab.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.33-rc3-ak/mm/slab.c
> ===================================================================
> --- linux-2.6.33-rc3-ak.orig/mm/slab.c
> +++ linux-2.6.33-rc3-ak/mm/slab.c
> @@ -3210,7 +3210,24 @@ retry:
> if (local_flags & __GFP_WAIT)
> local_irq_enable();
> kmem_flagcheck(cache, flags);
> - obj = kmem_getpages(cache, local_flags, numa_node_id());
> +
> + /*
> + * Node not set up yet? Try one that the cache has been set up
> + * for.
> + */
> + nid = numa_node_id();
> + if (cache->nodelists[nid] == NULL) {
> + for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) {
> + nid = zone_to_nid(zone);
> + if (cache->nodelists[nid])
> + break;

If you set a bit in a nodemask_t everytime ____cache_alloc_node() fails in
the previous for_each_zone_zonelist() iteration, you could just iterate
that nodemask here without duplicating the zone_to_nid() and
cache->nodelists[nid] != NULL check.
nid = numa_node_id();
if (!cache->nodelists[nid])
for_each_node_mask(nid, allowed_nodes) {
obj = kmem_getpages(cache, local_flags, nid);
if (obj)
break;
}
else
obj = kmem_getpages(cache, local_flags, nid);
This way you can try all allowed nodes for memory instead of just one when
cache->nodelists[numa_node_id()] == NULL.

> + }
> + if (!cache->nodelists[nid])
> + return NULL;
> + }
> +
> +
> + obj = kmem_getpages(cache, local_flags, nid);
> if (local_flags & __GFP_WAIT)
> local_irq_disable();
> if (obj) {


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