Re: [PATCH v3 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting

John Hubbard
2020-02-03T21:04:08Z

On 2/3/20 5:53 AM, Kirill A. Shutemov wrote:
> On Fri, Jan 31, 2020 at 07:40:27PM -0800, John Hubbard wrote:
>> diff --git a/mm/gup.c b/mm/gup.c
>> index c10d0d051c5b..9fe61d15fc0e 100644
>> --- a/mm/gup.c
>> +++ b/mm/gup.c
>> @@ -29,6 +29,19 @@ struct follow_page_context {
>> unsigned int page_mask;
>> };
>>
>> +#ifdef CONFIG_DEBUG_VM
>
> Why under CONFIG_DEBUG_VM? There's nothing about this in the cover letter.
>

Early on, gup_benchmark showed a really significant slowdown from using these
counters. And I don't doubt that it's still the case.

I'll re-measure and add a short summary and a few numbers to the patch commit
description, and to the v4 cover letter.

thanks,
--
John Hubbard
NVIDIA

>> +static inline void __update_proc_vmstat(struct page *page,
>> + enum node_stat_item item, int count)
>> +{
>> + mod_node_page_state(page_pgdat(page), item, count);
>> +}
>> +#else
>> +static inline void __update_proc_vmstat(struct page *page,
>> + enum node_stat_item item, int count)
>> +{
>> +}
>> +#endif
>> +
>> static void hpage_pincount_add(struct page *page, int refs)
>> {
>> VM_BUG_ON_PAGE(!hpage_pincount_available(page), page);