From: Yang Shi <shy828301@gmail.com>
To: Yu Zhao <yuzhao@google.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Alexander Duyck" <alexander.h.duyck@linux.intel.com>,
"Huang Ying" <ying.huang@intel.com>,
"David Hildenbrand" <david@redhat.com>,
"Michal Hocko" <mhocko@suse.com>,
"Yang Shi" <yang.shi@linux.alibaba.com>, "Qian Cai" <cai@lca.pw>,
"Mel Gorman" <mgorman@suse.de>,
"Nicholas Piggin" <npiggin@gmail.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
"Hugh Dickins" <hughd@google.com>,
"Linux MM" <linux-mm@kvack.org>,
"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>,
"Joonsoo Kim" <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v2 2/3] mm: remove superfluous __ClearPageActive()
Date: Wed, 19 Aug 2020 16:04:47 -0700 [thread overview]
Message-ID: <CAHbLzkrLK3gkeA2_B7jyf99jmA0yvV0fQE53sqOLHyocaCGDSw@mail.gmail.com> (raw)
In-Reply-To: <20200818184704.3625199-2-yuzhao@google.com>
On Tue, Aug 18, 2020 at 11:47 AM Yu Zhao <yuzhao@google.com> wrote:
>
> To activate a page, mark_page_accessed() always holds a reference
> on it. It either gets a new reference when adding a page to
> lru_pvecs.activate_page or reuses an existing one it previously
> got when it added a page to lru_pvecs.lru_add. So it doesn't call
> SetPageActive() on a page that doesn't have any reference left.
> Therefore, the race is impossible these days (I didn't brother to
> dig into its history).
>
> For other paths, namely reclaim and migration, a reference count is
> always held while calling SetPageActive() on a page.
>
> SetPageSlabPfmemalloc() also uses SetPageActive(), but it's irrelevant
> to LRU pages.
Seems fine to me. Reviewed-by: Yang Shi <shy828301@gmail.com>
>
> Signed-off-by: Yu Zhao <yuzhao@google.com>
> ---
> mm/memremap.c | 2 --
> mm/swap.c | 2 --
> 2 files changed, 4 deletions(-)
>
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 03e38b7a38f1..3a06eb91cb59 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -451,8 +451,6 @@ void free_devmap_managed_page(struct page *page)
> return;
> }
>
> - /* Clear Active bit in case of parallel mark_page_accessed */
> - __ClearPageActive(page);
> __ClearPageWaiters(page);
>
> mem_cgroup_uncharge(page);
> diff --git a/mm/swap.c b/mm/swap.c
> index 25c4043491b3..999a84dbe12c 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -900,8 +900,6 @@ void release_pages(struct page **pages, int nr)
> del_page_from_lru_list(page, lruvec, page_off_lru(page));
> }
>
> - /* Clear Active bit in case of parallel mark_page_accessed */
> - __ClearPageActive(page);
> __ClearPageWaiters(page);
>
> list_add(&page->lru, &pages_to_free);
> --
> 2.28.0.220.ged08abb693-goog
>
>
next prev parent reply other threads:[~2020-08-19 23:05 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-18 18:47 [PATCH v2 1/3] mm: remove activate_page() from unuse_pte() Yu Zhao
2020-08-18 18:47 ` [PATCH v2 2/3] mm: remove superfluous __ClearPageActive() Yu Zhao
2020-08-19 23:04 ` Yang Shi [this message]
2020-08-18 18:47 ` [PATCH v2 3/3] mm: remove superfluous __ClearPageWaiters() Yu Zhao
2020-08-19 23:06 ` Yang Shi
2020-08-19 23:39 ` Yu Zhao
2020-08-20 0:16 ` Yang Shi
2020-08-20 6:18 ` Michal Hocko
2020-08-20 8:12 ` Yu Zhao
2020-08-19 22:16 ` [PATCH v2 1/3] mm: remove activate_page() from unuse_pte() Yang Shi
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