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

Muchun Song
2020-12-10T16:21:53Z

On Thu, Dec 10, 2020 at 9:29 PM Muchun Song <songmuchun@bytedance.com> wrote:
>
> 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.

Hi Oscar,

Because this is an optimization for code, I leave it in this
separate patch. Do you still suggest squash this with
patch#10? Thanks.

>
> >
> > --
> > Oscar Salvador
> > SUSE L3
>
>
>
> --
> Yours,
> Muchun

--
Yours,
Muchun