Messages in this thread | | | Subject | Re: [External] Re: [PATCH v3 05/21] mm/hugetlb: Introduce pgtable allocation/freeing helpers | From | Mike Kravetz <> | Date | Thu, 12 Nov 2020 16:35:58 -0800 |
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On 11/10/20 7:41 PM, Muchun Song wrote: > On Wed, Nov 11, 2020 at 8:47 AM Mike Kravetz <mike.kravetz@oracle.com> wrote: >> >> On 11/8/20 6:10 AM, Muchun Song wrote: >> I am reading the code incorrectly it does not appear page->lru (of the huge >> page) is being used for this purpose. Is that correct? >> >> If it is correct, would using page->lru of the huge page make this code >> simpler? I am just missing the reason why you are using >> page_huge_pte(page)->lru > > For 1GB HugeTLB pages, we should pre-allocate more than one page > table. So I use a linked list. The page_huge_pte(page) is the list head. > Because the page->lru shares storage with page->pmd_huge_pte.
Sorry, but I do not understand the statement page->lru shares storage with page->pmd_huge_pte. Are you saying they are both in head struct page of the huge page?
Here is what I was suggesting. If we just use page->lru for the list then vmemmap_pgtable_prealloc() could be coded like the following:
static int vmemmap_pgtable_prealloc(struct hstate *h, struct page *page) { struct page *pte_page, *t_page; unsigned int nr = pgtable_pages_to_prealloc_per_hpage(h);
if (!nr) return 0;
/* Store preallocated pages on huge page lru list */ INIT_LIST_HEAD(&page->lru);
while (nr--) { pte_t *pte_p;
pte_p = pte_alloc_one_kernel(&init_mm); if (!pte_p) goto out; list_add(&virt_to_page(pte_p)->lru, &page->lru); }
return 0; out: list_for_each_entry_safe(pte_page, t_page, &page->lru, lru) pte_free_kernel(&init_mm, page_to_virt(pte_page)); return -ENOMEM; }
By doing this we could eliminate the routines, vmemmap_pgtable_init() vmemmap_pgtable_deposit() vmemmap_pgtable_withdraw() and simply use the list manipulation routines.
To me, that looks simpler than the proposed code in this patch. -- Mike Kravetz
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