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Message-ID: <2154ede0-aac1-c802-5470-3648113fcaff@linux.dev>
Date: Wed, 30 Aug 2023 16:23:05 +0800
From: Muchun Song <muchun.song@...ux.dev>
To: Mike Kravetz <mike.kravetz@...cle.com>,
Joao Martins <joao.m.martins@...cle.com>
Cc: Muchun Song <songmuchun@...edance.com>,
Oscar Salvador <osalvador@...e.de>,
David Hildenbrand <david@...hat.com>,
Miaohe Lin <linmiaohe@...wei.com>,
David Rientjes <rientjes@...gle.com>,
Anshuman Khandual <anshuman.khandual@....com>,
Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
Barry Song <song.bao.hua@...ilicon.com>,
Michal Hocko <mhocko@...e.com>,
Matthew Wilcox <willy@...radead.org>,
Xiongchun Duan <duanxiongchun@...edance.com>,
Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 11/12] hugetlb: batch TLB flushes when freeing vmemmap
On 2023/8/26 03:04, Mike Kravetz wrote:
> From: Joao Martins <joao.m.martins@...cle.com>
>
> Now that a list of pages is deduplicated at once, the TLB
> flush can be batched for all vmemmap pages that got remapped.
>
> Add a flags field and pass whether it's a bulk allocation or
> just a single page to decide to remap.
>
> The TLB flush is global as we don't have guarantees from caller
> that the set of folios is contiguous, or to add complexity in
> composing a list of kVAs to flush.
>
> Modified by Mike Kravetz to perform TLB flush on single folio if an
> error is encountered.
>
> Signed-off-by: Joao Martins <joao.m.martins@...cle.com>
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
> ---
> mm/hugetlb_vmemmap.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> index 904a64fe5669..a2fc7b03ac6b 100644
> --- a/mm/hugetlb_vmemmap.c
> +++ b/mm/hugetlb_vmemmap.c
> @@ -36,6 +36,7 @@ struct vmemmap_remap_walk {
> unsigned long reuse_addr;
> struct list_head *vmemmap_pages;
> #define VMEMMAP_REMAP_ONLY_SPLIT BIT(0)
> +#define VMEMMAP_REMAP_BULK_PAGES BIT(1)
We could reuse the flag (as I suggest VMEMMAP_SPLIT_WITHOUT_FLUSH)
proposed in the patch 10. When I saw this patch, I think the name
is not suitable, maybe VMEMMAP_WITHOUT_TLB_FLUSH is better.
Thanks.
> unsigned long flags;
> };
>
> @@ -211,7 +212,8 @@ static int vmemmap_remap_range(unsigned long start, unsigned long end,
> return ret;
> } while (pgd++, addr = next, addr != end);
>
> - if (!(walk->flags & VMEMMAP_REMAP_ONLY_SPLIT))
> + if (!(walk->flags &
> + (VMEMMAP_REMAP_ONLY_SPLIT | VMEMMAP_REMAP_BULK_PAGES)))
> flush_tlb_kernel_range(start, end);
>
> return 0;
> @@ -377,7 +379,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
> .remap_pte = vmemmap_remap_pte,
> .reuse_addr = reuse,
> .vmemmap_pages = &vmemmap_pages,
> - .flags = 0,
> + .flags = !bulk_pages ? 0 : VMEMMAP_REMAP_BULK_PAGES,
> };
> int nid = page_to_nid((struct page *)start);
> gfp_t gfp_mask = GFP_KERNEL | __GFP_THISNODE | __GFP_NORETRY |
> @@ -427,6 +429,7 @@ static int vmemmap_remap_free(unsigned long start, unsigned long end,
> .remap_pte = vmemmap_restore_pte,
> .reuse_addr = reuse,
> .vmemmap_pages = &vmemmap_pages,
> + .flags = 0,
> };
>
> vmemmap_remap_range(reuse, end, &walk);
> @@ -700,6 +703,8 @@ void hugetlb_vmemmap_optimize_folios(struct hstate *h, struct list_head *folio_l
> list_for_each_entry(folio, folio_list, lru)
> hugetlb_vmemmap_optimize_bulk(h, &folio->page, &vmemmap_pages);
>
> + flush_tlb_kernel_range(0, TLB_FLUSH_ALL);
> +
> free_vmemmap_page_list(&vmemmap_pages);
> }
>
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