Messages in this thread | | | Date | Fri, 16 Jan 2015 16:02:04 -0800 | From | Andrew Morton <> | Subject | Re: [PATCH V3] mm/thp: Allocate transparent hugepages on local node |
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On Fri, 16 Jan 2015 12:56:36 +0530 "Aneesh Kumar K.V" <aneesh.kumar@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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