On Mon, 16 Mar 2020 15:59:47 +0800 qiwuchen55@xxxxxxxxx wrote:
> From: chenqiwu <chenqiwu@xxxxxxxxxx>
>
> Remove duplicated pfn_to_section_nr() in pfn_valid() and pfn_present()
> to increase executing efficiency of code.
>
> ...
>
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -1358,10 +1358,11 @@ static inline int pfn_section_valid(struct mem_section *ms, unsigned long pfn)
> static inline int pfn_valid(unsigned long pfn)
> {
> struct mem_section *ms;
> + unsigned long sec_nr = pfn_to_section_nr(pfn);
>
> - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> + if (sec_nr >= NR_MEM_SECTIONS)
> return 0;
> - ms = __nr_to_section(pfn_to_section_nr(pfn));
> + ms = __nr_to_section(sec_nr);
> if (!valid_section(ms))
> return 0;
> /*
> @@ -1374,9 +1375,11 @@ static inline int pfn_valid(unsigned long pfn)
>
> static inline int pfn_present(unsigned long pfn)
> {
> - if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
> + unsigned long sec_nr = pfn_to_section_nr(pfn);
> +
> + if (sec_nr >= NR_MEM_SECTIONS)
> return 0;
> - return present_section(__nr_to_section(pfn_to_section_nr(pfn)));
> + return present_section(__nr_to_section(sec_nr));
> }
>
The compiler already makes this optimization (pfn_to_section_nr() is
very simple). Generated code appears to be identical.
I guess this patch could be sold as a cleanup, but I don't think it's
worthwhile, really.
