On Tue, Nov 10, 2020 at 1:21 AM Oscar Salvador <osalvador@xxxxxxx> wrote:
>
> On Sun, Nov 08, 2020 at 10:10:57PM +0800, Muchun Song wrote:
> > +static inline unsigned int pgtable_pages_to_prealloc_per_hpage(struct hstate *h)
> > +{
> > + unsigned long vmemmap_size = vmemmap_pages_size_per_hpage(h);
> > +
> > + /*
> > + * No need pre-allocate page tabels when there is no vmemmap pages
> > + * to free.
> s /tabels/tables/
Thanks.
>
> > +static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page)
> > +{
> > + int i;
> > + pgtable_t pgtable;
> > + unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h);
> > +
> > + if (!nr)
> > + return 0;
> > +
> > + vmemmap_pgtable_init(page);
> > +
> > + for (i = 0; i < nr; i++) {
> > + pte_t *pte_p;
> > +
> > + pte_p = pte_alloc_one_kernel(&init_mm);
> > + if (!pte_p)
> > + goto out;
> > + vmemmap_pgtable_deposit(page, virt_to_page(pte_p));
> > + }
> > +
> > + return 0;
> > +out:
> > + while (i-- && (pgtable = vmemmap_pgtable_withdraw(page)))
> > + pte_free_kernel(&init_mm, page_to_virt(pgtable));
>
> would not be enough to:
>
> while (pgtable = vmemmap_pgtable_withdrag(page))
> pte_free_kernel(&init_mm, page_to_virt(pgtable));
The vmemmap_pgtable_withdraw can not return NULL. So we can not
drop the "i--".
>
> > + return -ENOMEM;
> > +}
> > +
> > +static void vmemmap_pgtable_free(struct hstate *h, struct page *page)
> > +{
> > + pgtable_t pgtable;
> > + unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h);
> > +
> > + if (!nr)
> > + return;
>
> We can get rid of "nr" and its check and keep only the check below, right?
Great, the check can go away.
> AFAICS, they go together, e.g: if page_huge_pte does not return null,
> it means that we preallocated a pagetable, and viceversa.
>
>
> > +
> > + pgtable = page_huge_pte(page);
> > + if (!pgtable)
> > + return;
> > +
> > + while (nr-- && (pgtable = vmemmap_pgtable_withdraw(page)))
> > + pte_free_kernel(&init_mm, page_to_virt(pgtable));
>
> Same as above, that "nr" can go?
Here "nr" can not go. Because the vmemmap_pgtable_withdraw can
not return NULL.
Thanks.
>
> --
> Oscar Salvador
> SUSE L3
--
Yours,
Muchun
