On 01/17/2015 01:02 AM, Andrew Morton wrote:
> 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?
Hm that could work, alloc_pages_vma already has an if (MPOL_INTERLEAVE) part, so
just put the THP specialities into an "else if (huge_page)" part there?
You could probably test for GFP_TRANSHUGE the same way as __alloc_pages_slowpath
does. There might be false positives theoretically, but is there anything else
that would use these flags and not be a THP?
>> +{
>> + 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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