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SubjectRe: [PATCH 5/6] Filter based on a nodemask as well as a gfp_mask
On Fri, 17 Aug 2007, Mel Gorman wrote:

> @@ -696,6 +696,16 @@ static inline struct zonelist *node_zone
> return &NODE_DATA(nid)->node_zonelist;
> }
>
> +static inline int zone_in_nodemask(unsigned long zone_addr,
> + nodemask_t *nodes)
> +{
> +#ifdef CONFIG_NUMA
> + return node_isset(zonelist_zone(zone_addr)->node, *nodes);
> +#else
> + return 1;
> +#endif /* CONFIG_NUMA */
> +}
> +

This is dereferencind the zone in a filtering operation. I wonder if
we could encode the node in the zone_addr as well? x86_64 aligns zones on
page boundaries. So we have 10 bits left after taking 2 for the zone id.

> -int cpuset_zonelist_valid_mems_allowed(struct zonelist *zl)
> +int cpuset_nodemask_valid_mems_allowed(nodemask_t *nodemask)
> {
> - int i;
> -
> - for (i = 0; zl->_zones[i]; i++) {
> - int nid = zone_to_nid(zonelist_zone(zl->_zones[i]));
> + int nid;
>
> + for_each_node_mask(nid, *nodemask)
> if (node_isset(nid, current->mems_allowed))
> return 1;
> - }
> +
> return 0;

Hmmm... This is equivalent to

nodemask_t temp;

nodes_and(temp, nodemask, current->mems_allowed);
return !nodes_empty(temp);

which avoids the loop over all nodes.

> - }
> - if (num == 0) {
> - kfree(zl);
> - return ERR_PTR(-EINVAL);
> + for_each_node_mask(nd, *nodemask) {
> + struct zone *z = &NODE_DATA(nd)->node_zones[k];
> + if (z->present_pages > 0)
> + return 1;

Here you could use an and with the N_HIGH_MEMORY or N_NORMAL_MEMORY
nodemask.

> @@ -1149,12 +1125,19 @@ unsigned slab_node(struct mempolicy *pol
> case MPOL_INTERLEAVE:
> return interleave_nodes(policy);
>
> - case MPOL_BIND:
> + case MPOL_BIND: {

No { } needed.
> /*
> * Follow bind policy behavior and start allocation at the
> * first node.
> */
> - return zone_to_nid(zonelist_zone(policy->v.zonelist->_zones[0]));
> + struct zonelist *zonelist;
> + unsigned long *z;
> + enum zone_type highest_zoneidx = gfp_zone(GFP_KERNEL);
> + zonelist = &NODE_DATA(numa_node_id())->node_zonelist;
> + z = first_zones_zonelist(zonelist, &policy->v.nodes,
> + highest_zoneidx);
> + return zone_to_nid(zonelist_zone(*z));
> + }
>
> case MPOL_PREFERRED:
> if (policy->v.preferred_node >= 0)

> @@ -1330,14 +1314,6 @@ struct mempolicy *__mpol_copy(struct mem
> }
> *new = *old;
> atomic_set(&new->refcnt, 1);
> - if (new->policy == MPOL_BIND) {
> - int sz = ksize(old->v.zonelist);
> - new->v.zonelist = kmemdup(old->v.zonelist, sz, GFP_KERNEL);
> - if (!new->v.zonelist) {
> - kmem_cache_free(policy_cache, new);
> - return ERR_PTR(-ENOMEM);
> - }
> - }
> return new;

That is a good optimization.

> @@ -1680,32 +1647,6 @@ void mpol_rebind_policy(struct mempolicy
> *mpolmask, *newmask);
> *mpolmask = *newmask;
> break;
> - case MPOL_BIND: {
> - nodemask_t nodes;
> - unsigned long *z;
> - struct zonelist *zonelist;
> -
> - nodes_clear(nodes);
> - for (z = pol->v.zonelist->_zones; *z; z++)
> - node_set(zone_to_nid(zonelist_zone(*z)), nodes);
> - nodes_remap(tmp, nodes, *mpolmask, *newmask);
> - nodes = tmp;
> -
> - zonelist = bind_zonelist(&nodes);
> -
> - /* If no mem, then zonelist is NULL and we keep old zonelist.
> - * If that old zonelist has no remaining mems_allowed nodes,
> - * then zonelist_policy() will "FALL THROUGH" to MPOL_DEFAULT.
> - */
> -
> - if (!IS_ERR(zonelist)) {
> - /* Good - got mem - substitute new zonelist */
> - kfree(pol->v.zonelist);
> - pol->v.zonelist = zonelist;
> - }
> - *mpolmask = *newmask;
> - break;
> - }

Simply dropped? We still need to recalculate the node_mask depending on
the new cpuset environment!
-
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