On Fri, 16 Jan 2015 12:56:36 +0530 "Aneesh Kumar K.V"
<aneesh.ku...@linux.vnet.ibm.com> wrote:
> This make sure that we try to allocate hugepages from local node if
> allowed by mempolicy. If we can't, we fallback to small page allocation
> based on mempolicy. This is based on the observation that allocating pages
> on local node is more beneficial than allocating hugepages on remote node.
The changelog is a bit incomplete. It doesn't describe the current
behaviour, nor what is wrong with it. What are the before-and-after
effects of this change?
And what might be the user-visible effects?
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -2030,6 +2030,46 @@ retry_cpuset:
> return page;
> }
>
> +struct page *alloc_hugepage_vma(gfp_t gfp, struct vm_area_struct *vma,
> + unsigned long addr, int order)
alloc_pages_vma() is nicely documented. alloc_hugepage_vma() is not
documented at all. This makes it a bit had for readers to work out the
difference!
Is it possible to scrunch them both into the same function? Probably
too messy?
> +{
> + struct page *page;
> + nodemask_t *nmask;
> + struct mempolicy *pol;
> + int node = numa_node_id();
> + unsigned int cpuset_mems_cookie;
> +
> +retry_cpuset:
> + pol = get_vma_policy(vma, addr);
> + cpuset_mems_cookie = read_mems_allowed_begin();
> +
> + if (pol->mode != MPOL_INTERLEAVE) {
> + /*
> + * For interleave policy, we don't worry about
> + * current node. Otherwise if current node is
> + * in nodemask, try to allocate hugepage from
> + * current node. Don't fall back to other nodes
> + * for THP.
> + */
This code isn't "interleave policy". It's everything *but* interleave
policy. Comment makes no sense!
> + nmask = policy_nodemask(gfp, pol);
> + if (!nmask || node_isset(node, *nmask)) {
> + mpol_cond_put(pol);
> + page = alloc_pages_exact_node(node, gfp, order);
> + if (unlikely(!page &&
> +
> read_mems_allowed_retry(cpuset_mems_cookie)))
> + goto retry_cpuset;
> + return page;
> + }
> + }
> + mpol_cond_put(pol);
> + /*
> + * if current node is not part of node mask, try
> + * the allocation from any node, and we can do retry
> + * in that case.
> + */
> + return alloc_pages_vma(gfp, order, vma, addr, node);
> +}
--
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