Re: [External] Re: [PATCH v8 12/12] mm/hugetlb: Optimize the code with the help of the compiler

Muchun Song
2020-12-10T13:31:43Z

On Thu, Dec 10, 2020 at 9:16 PM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Thu, Dec 10, 2020 at 08:14:18PM +0800, Muchun Song wrote:
> > Yeah, you are right. But if we do this check can make the code simple.
> >
> > For example, here is a code snippet.
> >
> > void func(void)
> > {
> > if (free_vmemmap_pages_per_hpage())
> > return;
> > /* Do something */
> > }
> >
> > With this patch, the func will be optimized to null when is_power_of_2
> > returns false.
> >
> > void func(void)
> > {
> > }
> >
> > Without this patch, the compiler cannot do this optimization.
>
> Ok, I misread the changelog.
>
> So, then is_hugetlb_free_vmemmap_enabled, free_huge_page_vmemmap,
> free_vmemmap_pages_per_hpage and hugetlb_vmemmap_init are optimized
> out, right?

Yes, that's right. I have disassembled to make sure of this. Thanks.

>
> --
> Oscar Salvador
> SUSE L3

--
Yours,
Muchun