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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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