On Wed 17-03-21 11:40:07, Feng Tang wrote:
[...]
> @@ -2301,10 +2300,26 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
> * does not allow the current node in its nodemask, we allocate
> * the standard way.
> */
> - if ((pol->mode == MPOL_PREFERRED ||
> - pol->mode == MPOL_PREFERRED_MANY) &&
> - !(pol->flags & MPOL_F_LOCAL))
> + if (pol->mode == MPOL_PREFERRED || !(pol->flags & MPOL_F_LOCAL)) {
> hpage_node = first_node(pol->nodes);
> + } else if (pol->mode == MPOL_PREFERRED_MANY) {
> + struct zoneref *z;
> +
> + /*
> + * In this policy, with direct reclaim, the normal
> + * policy based allocation will do the right thing - try
> + * twice using the preferred nodes first, and all nodes
> + * second.
> + */
> + if (gfp & __GFP_DIRECT_RECLAIM) {
> + page = alloc_pages_policy(pol, gfp, order, NUMA_NO_NODE);
> + goto out;
> + }
> +
> + z = first_zones_zonelist(node_zonelist(numa_node_id(), GFP_HIGHUSER),
> + gfp_zone(GFP_HIGHUSER), &pol->nodes);
> + hpage_node = zone_to_nid(z->zone);
> + }
>
> nmask = policy_nodemask(gfp, pol);
> if (!nmask || node_isset(hpage_node, *nmask)) {
> @@ -2330,9 +2345,7 @@ alloc_pages_vma(gfp_t gfp, int order, struct vm_area_struct *vma,
> }
> }
>
> - nmask = policy_nodemask(gfp, pol);
> - preferred_nid = policy_node(gfp, pol, node);
> - page = __alloc_pages_nodemask(gfp, order, preferred_nid, nmask);
> + page = alloc_pages_policy(pol, gfp, order, NUMA_NO_NODE);
> mpol_cond_put(pol);
> out:
> return page;
OK, it took me a while to grasp this but the code is a mess I have to
say. Not that it was an act of beauty before but this just makes it much
harder to follow. And alloc_pages_policy doesn't really help I have to
say. I would have expected that a dedicated alloc_pages_preferred and a
general fallback to __alloc_pages_nodemask would have been much easier
to follow.
--
Michal Hocko
SUSE Labs
