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From: Johannes Weiner <hannes@cmpxchg.org>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: akpm@linux-foundation.org, mgorman@techsingularity.net,
	tj@kernel.org, hughd@google.com, khlebnikov@yandex-team.ru,
	daniel.m.jordan@oracle.com, willy@infradead.org, lkp@intel.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	cgroups@vger.kernel.org, shakeelb@google.com,
	iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com,
	kirill@shutemov.name, alexander.duyck@gmail.com,
	rong.a.chen@intel.com, mhocko@suse.com, vdavydov.dev@gmail.com,
	shy828301@gmail.com, Vlastimil Babka <vbabka@suse.cz>,
	Minchan Kim <minchan@kernel.org>
Subject: Re: [PATCH v20 08/20] mm: page_idle_get_page() does not need lru_lock
Date: Mon, 2 Nov 2020 09:41:10 -0500	[thread overview]
Message-ID: <20201102144110.GB724984@cmpxchg.org> (raw)
In-Reply-To: <1603968305-8026-9-git-send-email-alex.shi@linux.alibaba.com>

On Thu, Oct 29, 2020 at 06:44:53PM +0800, Alex Shi wrote:
> From: Hugh Dickins <hughd@google.com>
> 
> It is necessary for page_idle_get_page() to recheck PageLRU() after
> get_page_unless_zero(), but holding lru_lock around that serves no
> useful purpose, and adds to lru_lock contention: delete it.
> 
> See https://lore.kernel.org/lkml/20150504031722.GA2768@blaptop for the
> discussion that led to lru_lock there; but __page_set_anon_rmap() now
> uses WRITE_ONCE(),

That doesn't seem to be the case in Linus's or Andrew's tree. Am I
missing a dependent patch series?

> and I see no other risk in page_idle_clear_pte_refs() using
> rmap_walk() (beyond the risk of racing PageAnon->PageKsm, mostly but
> not entirely prevented by page_count() check in ksm.c's
> write_protect_page(): that risk being shared with page_referenced()
> and not helped by lru_lock).

Isn't it possible, as per Minchan's description, for page->mapping to
point to a struct anon_vma without PAGE_MAPPING_ANON set, and rmap
thinking it's looking at a struct address_space?

  reply	other threads:[~2020-11-02 14:42 UTC|newest]

Thread overview: 67+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-29 10:44 [PATCH v20 00/20] per memcg lru lock Alex Shi
2020-10-29 10:44 ` [PATCH v20 01/20] mm/memcg: warning on !memcg after readahead page charged Alex Shi
2020-10-29 13:43   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 02/20] mm/memcg: bail early from swap accounting if memcg disabled Alex Shi
2020-10-29 13:46   ` Johannes Weiner
2020-10-30  2:27     ` Alex Shi
2020-10-30 14:04       ` Johannes Weiner
2020-10-31  1:13         ` Alex Shi
2020-10-29 10:44 ` [PATCH v20 03/20] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi
2020-10-29 13:47   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 04/20] mm/thp: use head for head page in lru_add_page_tail Alex Shi
2020-10-29 13:50   ` Johannes Weiner
2020-10-30  2:46     ` Alex Shi
2020-10-30 13:52       ` Johannes Weiner
2020-10-31  1:14         ` Alex Shi
2020-11-02 16:03       ` Matthew Wilcox
2020-11-03  2:43         ` Alex Shi
2020-10-29 10:44 ` [PATCH v20 05/20] mm/thp: Simplify lru_add_page_tail() Alex Shi
2020-10-29 14:00   ` Johannes Weiner
2020-10-30  2:48   ` Alex Shi
2020-10-29 10:44 ` [PATCH v20 06/20] mm/thp: narrow lru locking Alex Shi
2020-10-29 10:44 ` [PATCH v20 07/20] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-11-02 14:20   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 08/20] mm: page_idle_get_page() does not need lru_lock Alex Shi
2020-11-02 14:41   ` Johannes Weiner [this message]
2020-11-02 14:49     ` Matthew Wilcox
2020-11-02 20:20       ` Johannes Weiner
2020-11-04 11:27         ` Alex Shi
2020-11-04 17:46           ` Johannes Weiner
2020-11-05  4:52             ` Alex Shi
2020-11-05  4:57               ` Matthew Wilcox
2020-11-05  5:03                 ` Alex Shi
2020-11-05 15:36                   ` Johannes Weiner
2020-11-05 15:43                     ` Matthew Wilcox
2020-11-06  1:11                     ` Alex Shi
2020-11-11  7:27     ` Hugh Dickins
2020-10-29 10:44 ` [PATCH v20 09/20] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2020-11-02 14:45   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 10/20] mm/swap.c: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi
2020-11-02 14:48   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 11/20] mm/lru: move lock into lru_note_cost Alex Shi
2020-10-29 13:42   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 12/20] mm/vmscan: remove lruvec reget in move_pages_to_lru Alex Shi
2020-11-02 14:52   ` Johannes Weiner
2020-11-03  2:51     ` Alex Shi
2020-10-29 10:44 ` [PATCH v20 13/20] mm/mlock: remove lru_lock on TestClearPageMlocked Alex Shi
2020-11-02 14:55   ` Johannes Weiner
2020-10-29 10:44 ` [PATCH v20 14/20] mm/mlock: remove __munlock_isolate_lru_page Alex Shi
2020-11-02 14:56   ` Johannes Weiner
2020-10-29 10:45 ` [PATCH v20 15/20] mm/lru: introduce TestClearPageLRU Alex Shi
2020-11-02 15:10   ` Johannes Weiner
2020-11-03  3:02     ` Alex Shi
2020-10-29 10:45 ` [PATCH v20 16/20] mm/compaction: do page isolation first in compaction Alex Shi
2020-11-02 15:18   ` Johannes Weiner
2020-10-29 10:45 ` [PATCH v20 17/20] mm/swap.c: serialize memcg changes in pagevec_lru_move_fn Alex Shi
2020-11-02 15:20   ` Johannes Weiner
2020-10-29 10:45 ` [PATCH v20 18/20] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-10-30  2:49   ` Alex Shi
2020-11-02 20:41     ` Johannes Weiner
2020-11-03  4:58       ` Alex Shi
2020-10-29 10:45 ` [PATCH v20 19/20] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-11-02 20:44   ` Johannes Weiner
2020-10-29 10:45 ` [PATCH v20 20/20] mm/lru: revise the comments of lru_lock Alex Shi
2020-11-02 20:46   ` Johannes Weiner
2020-11-04 11:55 ` [PATCH v20 00/20] per memcg lru lock Alex Shi
2020-11-04 16:59   ` Johannes Weiner
2020-11-05  5:07     ` Alex Shi

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