From: huang ying <huang.ying.caritas@gmail.com> To: Alex Shi <alex.shi@linux.alibaba.com> Cc: Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@techsingularity.net>, Tejun Heo <tj@kernel.org>, Hugh Dickins <hughd@google.com>, khlebnikov@yandex-team.ru, daniel.m.jordan@oracle.com, willy@infradead.org, Johannes Weiner <hannes@cmpxchg.org>, lkp@intel.com, linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>, cgroups@vger.kernel.org, Shakeel Butt <shakeelb@google.com>, iamjoonsoo.kim@lge.com, richard.weiyang@gmail.com, kirill@shutemov.name, alexander.duyck@gmail.com, kernel test robot <rong.a.chen@intel.com>, Michal Hocko <mhocko@suse.com>, Vladimir Davydov <vdavydov.dev@gmail.com>, shy828301@gmail.com, Vlastimil Babka <vbabka@suse.cz>, Minchan Kim <minchan@kernel.org> Subject: Re: [PATCH v21 07/19] mm: page_idle_get_page() does not need lru_lock Date: Wed, 11 Nov 2020 16:17:17 +0800 [thread overview] Message-ID: <CAC=cRTPYgD4qi=-dj=PY4804Y96k7fU065vLA8mNBmucZTnFSw@mail.gmail.com> (raw) In-Reply-To: <1604566549-62481-8-git-send-email-alex.shi@linux.alibaba.com> On Thu, Nov 5, 2020 at 4:56 PM Alex Shi <alex.shi@linux.alibaba.com> 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(), 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). > > Signed-off-by: Hugh Dickins <hughd@google.com> > Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com> > Cc: Andrew Morton <akpm@linux-foundation.org> > Cc: Vladimir Davydov <vdavydov.dev@gmail.com> > Cc: Vlastimil Babka <vbabka@suse.cz> > Cc: Minchan Kim <minchan@kernel.org> > Cc: Alex Shi <alex.shi@linux.alibaba.com> > Cc: linux-mm@kvack.org > Cc: linux-kernel@vger.kernel.org > --- > mm/page_idle.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/mm/page_idle.c b/mm/page_idle.c > index 057c61df12db..64e5344a992c 100644 > --- a/mm/page_idle.c > +++ b/mm/page_idle.c > @@ -32,19 +32,15 @@ > static struct page *page_idle_get_page(unsigned long pfn) > { > struct page *page = pfn_to_online_page(pfn); > - pg_data_t *pgdat; > > if (!page || !PageLRU(page) || > !get_page_unless_zero(page)) > return NULL; > > - pgdat = page_pgdat(page); > - spin_lock_irq(&pgdat->lru_lock); get_page_unless_zero() is a full memory barrier. But do we need a compiler barrier here to prevent the compiler to cache PageLRU() results here? Otherwise looks OK to me, Acked-by: "Huang, Ying" <ying.huang@intel.com> Best Regards, Huang, Ying > if (unlikely(!PageLRU(page))) { > put_page(page); > page = NULL; > } > - spin_unlock_irq(&pgdat->lru_lock); > return page; > } > > -- > 1.8.3.1 > >
WARNING: multiple messages have this Message-ID (diff)
From: huang ying <huang.ying.caritas-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> To: Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Mel Gorman <mgorman-3eNAlZScCAx27rWaFMvyedHuzzzSOjJt@public.gmane.org>, Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>, Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, khlebnikov-XoJtRXgx1JseBXzfvpsJ4g@public.gmane.org, daniel.m.jordan-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org, willy-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org, Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>, lkp-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org, linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Shakeel Butt <shakeelb-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>, iamjoonsoo.kim-Hm3cg6mZ9cc@public.gmane.org, richard.weiyang-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org, alexander.duyck-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, kernel test robot <rong.a.chen-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>, Michal Hocko <mhocko-IBi9RG/b67k@public.gmane.org>, Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, shy828301-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org, Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>, Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Subject: Re: [PATCH v21 07/19] mm: page_idle_get_page() does not need lru_lock Date: Wed, 11 Nov 2020 16:17:17 +0800 [thread overview] Message-ID: <CAC=cRTPYgD4qi=-dj=PY4804Y96k7fU065vLA8mNBmucZTnFSw@mail.gmail.com> (raw) In-Reply-To: <1604566549-62481-8-git-send-email-alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> On Thu, Nov 5, 2020 at 4:56 PM Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> wrote: > > From: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> > > 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(), 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). > > Signed-off-by: Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org> > Signed-off-by: Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> > Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org> > Cc: Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> > Cc: Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org> > Cc: Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> > Cc: Alex Shi <alex.shi-KPsoFbNs7GizrGE5bRqYAgC/G2K4zDHf@public.gmane.org> > Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org > Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > --- > mm/page_idle.c | 4 ---- > 1 file changed, 4 deletions(-) > > diff --git a/mm/page_idle.c b/mm/page_idle.c > index 057c61df12db..64e5344a992c 100644 > --- a/mm/page_idle.c > +++ b/mm/page_idle.c > @@ -32,19 +32,15 @@ > static struct page *page_idle_get_page(unsigned long pfn) > { > struct page *page = pfn_to_online_page(pfn); > - pg_data_t *pgdat; > > if (!page || !PageLRU(page) || > !get_page_unless_zero(page)) > return NULL; > > - pgdat = page_pgdat(page); > - spin_lock_irq(&pgdat->lru_lock); get_page_unless_zero() is a full memory barrier. But do we need a compiler barrier here to prevent the compiler to cache PageLRU() results here? Otherwise looks OK to me, Acked-by: "Huang, Ying" <ying.huang-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org> Best Regards, Huang, Ying > if (unlikely(!PageLRU(page))) { > put_page(page); > page = NULL; > } > - spin_unlock_irq(&pgdat->lru_lock); > return page; > } > > -- > 1.8.3.1 > >
next prev parent reply other threads:[~2020-11-11 8:17 UTC|newest] Thread overview: 111+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-11-05 8:55 [PATCH v21 00/19] per memcg lru lock Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 01/19] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 02/19] mm/thp: use head for head page in lru_add_page_tail Alex Shi 2020-11-05 8:55 ` [PATCH v21 03/19] mm/thp: Simplify lru_add_page_tail() Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 04/19] mm/thp: narrow lru locking Alex Shi 2020-11-05 8:55 ` [PATCH v21 05/19] mm/vmscan: remove unnecessary lruvec adding Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-11 12:36 ` Vlastimil Babka 2020-11-11 12:36 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 06/19] mm/rmap: stop store reordering issue on page->mapping Alex Shi 2020-11-06 1:20 ` Alex Shi 2020-11-06 1:20 ` Alex Shi 2020-11-10 19:06 ` Johannes Weiner 2020-11-11 7:41 ` Hugh Dickins 2020-11-11 7:41 ` Hugh Dickins 2020-11-05 8:55 ` [PATCH v21 07/19] mm: page_idle_get_page() does not need lru_lock Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-10 19:01 ` Johannes Weiner 2020-11-11 8:17 ` huang ying [this message] 2020-11-11 8:17 ` huang ying 2020-11-11 8:17 ` huang ying 2020-11-11 12:52 ` Vlastimil Babka 2020-11-11 12:52 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 08/19] mm/memcg: add debug checking in lock_page_memcg Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 09/19] mm/swap.c: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi 2020-11-05 8:55 ` [PATCH v21 10/19] mm/lru: move lock into lru_note_cost Alex Shi 2020-11-05 8:55 ` [PATCH v21 11/19] mm/vmscan: remove lruvec reget in move_pages_to_lru Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 12/19] mm/mlock: remove lru_lock on TestClearPageMlocked Alex Shi 2020-11-11 13:03 ` Vlastimil Babka 2020-11-11 13:03 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 13/19] mm/mlock: remove __munlock_isolate_lru_page Alex Shi 2020-11-11 13:07 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 14/19] mm/lru: introduce TestClearPageLRU Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-11 13:36 ` Vlastimil Babka 2020-11-12 2:03 ` Hugh Dickins 2020-11-12 2:03 ` Hugh Dickins 2020-11-12 11:24 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 15/19] mm/compaction: do page isolation first in compaction Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-11 17:12 ` Vlastimil Babka 2020-11-11 17:12 ` Vlastimil Babka 2020-11-12 2:28 ` Hugh Dickins 2020-11-12 2:28 ` Hugh Dickins 2020-11-12 3:35 ` Alex Shi 2020-11-12 3:35 ` Alex Shi 2020-11-12 11:25 ` Vlastimil Babka 2020-11-12 11:25 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 16/19] mm/swap.c: serialize memcg changes in pagevec_lru_move_fn Alex Shi 2020-11-11 18:00 ` Vlastimil Babka 2020-11-11 18:00 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 17/19] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-05 13:43 ` Alex Shi 2020-11-05 13:43 ` Alex Shi 2020-11-06 7:48 ` Alex Shi 2020-11-06 7:48 ` Alex Shi 2020-11-10 18:54 ` Johannes Weiner 2020-11-10 18:54 ` Johannes Weiner 2020-11-11 17:46 ` Vlastimil Babka 2020-11-11 17:46 ` Vlastimil Babka 2020-11-11 17:59 ` Vlastimil Babka 2020-11-12 12:19 ` Vlastimil Babka 2020-11-12 12:19 ` Vlastimil Babka 2020-11-12 14:19 ` Alex Shi 2020-11-12 14:19 ` Alex Shi 2020-11-05 8:55 ` [PATCH v21 18/19] mm/lru: introduce the relock_page_lruvec function Alex Shi 2020-11-05 8:55 ` Alex Shi 2020-11-06 7:50 ` Alex Shi 2020-11-06 7:50 ` Alex Shi 2020-11-10 18:59 ` Johannes Weiner 2020-11-10 18:59 ` Johannes Weiner 2020-11-12 12:31 ` Vlastimil Babka 2020-11-12 12:31 ` Vlastimil Babka 2020-11-05 8:55 ` [PATCH v21 19/19] mm/lru: revise the comments of lru_lock Alex Shi 2020-11-12 12:37 ` Vlastimil Babka 2020-11-12 12:37 ` Vlastimil Babka 2020-11-10 12:14 ` [PATCH v21 00/19] per memcg lru lock Alex Shi 2020-11-10 12:14 ` Alex Shi 2020-11-16 3:45 ` Alex Shi 2020-11-16 3:45 ` Alex Shi 2020-12-15 0:47 ` Andrew Morton 2020-12-15 0:47 ` Andrew Morton 2020-12-15 2:16 ` Hugh Dickins 2020-12-15 2:16 ` Hugh Dickins 2020-12-15 2:16 ` Hugh Dickins 2020-12-15 2:28 ` Andrew Morton 2020-12-15 2:28 ` Andrew Morton 2021-01-05 19:30 ` Qian Cai 2021-01-05 19:30 ` Qian Cai 2021-01-05 19:30 ` Qian Cai 2021-01-05 19:42 ` Shakeel Butt 2021-01-05 19:42 ` Shakeel Butt 2021-01-05 19:42 ` Shakeel Butt 2021-01-05 20:11 ` Qian Cai 2021-01-05 20:11 ` Qian Cai 2021-01-05 20:11 ` Qian Cai 2021-01-05 21:35 ` Hugh Dickins 2021-01-05 21:35 ` Hugh Dickins 2021-01-05 21:35 ` Hugh Dickins 2021-01-05 22:01 ` Qian Cai 2021-01-05 22:01 ` Qian Cai 2021-01-05 22:01 ` Qian Cai 2021-01-06 3:10 ` Hugh Dickins 2021-01-06 3:10 ` Hugh Dickins 2021-01-06 3:10 ` Hugh Dickins
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