Davidlohr Bueso <dave@xxxxxxxxxxxx> writes:
> On Fri, 2015-01-16 at 16:02 -0800, Andrew Morton wrote:
>> On Fri, 16 Jan 2015 12:56:36 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxxxxxxx> 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?
>
> I'd be interested in any performance data. I'll run this by a 4 node box
> next week.
Thanks.
>
>>
>> > --- 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!
>
> May I add that, while a nit, this indentation is quite ugly:
I updated that and replied here
http://article.gmane.org/gmane.linux.kernel/1868545. Let me know what you think.
>
>>
>> > + 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;
>> > + }
>> > + }
>
> Improving it makes the code visually easier on the eye. So this should
> be considered if another re-spin of the patch is to be done anyway. Just
> jump to the mpol refcounting and be done when 'pol->mode ==
> MPOL_INTERLEAVE'.
>
-aneesh
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