Re: [PATCH] [1/4] SLAB: Handle node-not-up case in fallback_alloc() v2

Nick Piggin
2010-02-15T06:04:16Z

On Thu, Feb 11, 2010 at 09:54:00PM +0100, 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.
>
> v2: Try to allocate from all nodes (David Rientjes)
>
> Signed-off-by: Andi Kleen <ak@linux.intel.com>
>
> ---
> mm/slab.c | 19 ++++++++++++++++++-
> 1 file changed, 18 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.32-memhotadd/mm/slab.c
> ===================================================================
> --- linux-2.6.32-memhotadd.orig/mm/slab.c
> +++ linux-2.6.32-memhotadd/mm/slab.c
> @@ -3188,7 +3188,24 @@ 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]) {
> + obj = kmem_getpages(cache, local_flags, nid);
> + if (obj)
> + break;
> + }
> + }
> + } else
> + obj = kmem_getpages(cache, local_flags, nid);
> +
> if (local_flags & __GFP_WAIT)
> local_irq_disable();
> if (obj) {

This is a better way to go anyway because it really is a proper
"fallback" alloc. I think that possibly used to work (ie. kmem_getpages
would be able to pass -1 for the node there) but got broken along the
line.

Although it's not such a hot path to begin with, care to put a branch
annotation there?

Acked-by: Nick Piggin <npiggin@suse.de>