Re: [External] Re: [PATCH v7 06/15] mm/hugetlb: Disable freeing vmemmap if struct page size is not power of two

[David Hildenbrand]

On 09.12.20 11:03, Muchun Song wrote:
> On Wed, Dec 9, 2020 at 5:57 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
>>
>> On 30.11.20 16:18, Muchun Song wrote:
>>> We only can free the tail vmemmap pages of HugeTLB to the buddy allocator
>>> when the size of struct page is a power of two.
>>>
>>> Signed-off-by: Muchun Song <songmuchun@xxxxxxxxxxxxx>
>>> ---
>>>  mm/hugetlb_vmemmap.c | 5 +++++
>>>  1 file changed, 5 insertions(+)
>>>
>>> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
>>> index 51152e258f39..ad8fc61ea273 100644
>>> --- a/mm/hugetlb_vmemmap.c
>>> +++ b/mm/hugetlb_vmemmap.c
>>> @@ -111,6 +111,11 @@ void __init hugetlb_vmemmap_init(struct hstate *h)
>>>       unsigned int nr_pages = pages_per_huge_page(h);
>>>       unsigned int vmemmap_pages;
>>>
>>> +     if (!is_power_of_2(sizeof(struct page))) {
>>> +             pr_info("disable freeing vmemmap pages for %s\n", h->name);
>>
>> I'd just drop that pr_info(). Users are able to observe that it's
>> working (below), so they are able to identify that it's not working as well.
> 
> The below is just a pr_debug. Do you suggest converting it to pr_info?

Good question. I wonder if users really have to know in most cases.
Maybe pr_debug() is good enough in environments where we want to debug
why stuff is not working as expected.

-- 
Thanks,

David / dhildenb