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Message-ID: <d833eb25-fd25-0211-2031-f3b4a5215139@nvidia.com>
Date: Thu, 4 Aug 2022 16:06:56 -0700
From: John Hubbard <jhubbard@...dia.com>
To: Alistair Popple <apopple@...dia.com>, linux-mm@...ck.org
Cc: akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
"Sierra Guiza, Alejandro (Alex)" <alex.sierra@....com>,
Chaitanya Kulkarni <kch@...dia.com>,
Dan Williams <dan.j.williams@...el.com>,
Felix Kuehling <Felix.Kuehling@....com>,
Jason Gunthorpe <jgg@...dia.com>,
Logan Gunthorpe <logang@...tatee.com>,
Miaohe Lin <linmiaohe@...wei.com>,
Muchun Song <songmuchun@...edance.com>,
Pasha Tatashin <pasha.tatashin@...een.com>,
Ralph Campbell <rcampbell@...dia.com>
Subject: Re: [PATCH] mm/gup.c: Refactor check_and_migrate_movable_pages()
On 8/3/22 20:22, Alistair Popple wrote:
> @@ -1970,29 +1968,25 @@ static long check_and_migrate_movable_pages(unsigned long nr_pages,
> drain_allow = false;
> }
>
> - if (folio_isolate_lru(folio)) {
> - isolation_error_count++;
> + if (folio_isolate_lru(folio))
> continue;
> - }
> +
> list_add_tail(&folio->lru, &movable_page_list);
> node_stat_mod_folio(folio,
> NR_ISOLATED_ANON + folio_is_file_lru(folio),
> folio_nr_pages(folio));
> }
>
> - if (!list_empty(&movable_page_list) || isolation_error_count ||
> - coherent_pages)
> - goto unpin_pages;
> -
> /*
> - * If list is empty, and no isolation errors, means that all pages are
> - * in the correct zone.
> + * All pages are still pinned and in the correct zone.
> */
> - return nr_pages;
> + if (list_empty(&movable_page_list) && !coherent_pages)
> + return 0;
>
At this point, a second part of the (rather long) routine begins. If I
were refactoring this, I'd split it into a top level routine that calls
the two parts:
check_and_migrate_movable_pages()
collect_migration_candidates()
unpin_and_migrate_pages()
...which I think would further help in working with this thing.
(I realize that this is additional work. And that it's best done as a
separate patch. And it's just a suggestion.)
> -unpin_pages:
> /*
> - * pages[i] might be NULL if any device coherent pages were found.
> + * Unpin all pages. If device coherent pages were found
> + * migrate_deivce_coherent_page() will have already dropped the pin and
"migrate_device_coherent_page()"
thanks,
--
John Hubbard
NVIDIA
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