Re: [External] Re: [PATCH v8 09/12] mm/hugetlb: Add a kernel parameter hugetlb_free_vmemmap

Muchun Song
2020-12-10T12:27:56Z

On Thu, Dec 10, 2020 at 7:41 PM Oscar Salvador <osalvador@suse.de> wrote:
>
> On Thu, Dec 10, 2020 at 11:55:23AM +0800, Muchun Song wrote:
> > +hugetlb_free_vmemmap
> > + When CONFIG_HUGETLB_PAGE_FREE_VMEMMAP is set, this enables freeing
> > + unused vmemmap pages associated each HugeTLB page.
> ^^^ with

Thanks.

>
> > - if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> > + if (is_hugetlb_free_vmemmap_enabled())
> > + err = vmemmap_populate_basepages(start, end, node, NULL);
> > + else if (end - start < PAGES_PER_SECTION * sizeof(struct page))
> > err = vmemmap_populate_basepages(start, end, node, NULL);
>
> Not sure if joining those in an OR makes se.se

Well, I can do it.

>
> > else if (boot_cpu_has(X86_FEATURE_PSE))
> > err = vmemmap_populate_hugepages(start, end, node, altmap);
> > @@ -1610,7 +1613,8 @@ void register_page_bootmem_memmap(unsigned long section_nr,
> > }
> > get_page_bootmem(section_nr, pud_page(*pud), MIX_SECTION_INFO);
> >
> > - if (!boot_cpu_has(X86_FEATURE_PSE)) {
> > + if (!boot_cpu_has(X86_FEATURE_PSE) ||
> > + is_hugetlb_free_vmemmap_enabled()) {
>
> I would add a variable at the beginning called "basepages_populated"
> that holds the result of those two conditions.
> I am not sure if it slightly improves the code as the conditions do
> not need to be rechecked, but the readibility a bit.

Agree. The condition does not need to be rechecked.
Will do in the next version. Thanks.

>
> > +bool hugetlb_free_vmemmap_enabled;
> > +
> > +static int __init early_hugetlb_free_vmemmap_param(char *buf)
> > +{
> > + if (!buf)
> > + return -EINVAL;
> > +
> > + /* We cannot optimize if a "struct page" crosses page boundaries. */
>
> I think this comment belongs to the last patch.
>

Thanks.

>
> --
> Oscar Salvador
> SUSE L3

--
Yours,
Muchun