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From: Alexander Duyck <alexander.duyck@gmail.com>
To: Alex Shi <alex.shi@linux.alibaba.com>
Cc: "Duyck, Alexander H" <alexander.h.duyck@intel.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	 Andrey Ryabinin <aryabinin@virtuozzo.com>,
	cgroups@vger.kernel.org,
	 Daniel Jordan <daniel.m.jordan@oracle.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	 Hugh Dickins <hughd@google.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	 Konstantin Khlebnikov <khlebnikov@yandex-team.ru>,
	"Kirill A. Shutemov" <kirill@shutemov.name>,
	 LKML <linux-kernel@vger.kernel.org>,
	linux-mm <linux-mm@kvack.org>,  kbuild test robot <lkp@intel.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	 Wei Yang <richard.weiyang@gmail.com>,
	Rong Chen <rong.a.chen@intel.com>,
	 Shakeel Butt <shakeelb@google.com>,
	Thomas Gleixner <tglx@linutronix.de>, Tejun Heo <tj@kernel.org>,
	 Matthew Wilcox <willy@infradead.org>,
	Yang Shi <yang.shi@linux.alibaba.com>
Subject: Re: [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid
Date: Sun, 2 Aug 2020 11:20:53 -0700
Message-ID: <CAKgT0UcDbzb_MXynzZANvJ_bV4VEguhxgOt2-hp4cNtvwE-r_Q@mail.gmail.com> (raw)
In-Reply-To: <0c0a415a-52a0-5c06-b4be-80cbd3cb49c2@linux.alibaba.com>

Feel free to fold it into your patches if you want.

I think Hugh was the one that had submitted a patch that addressed it,
and it looks like you folded that into your v17 set. It was probably
what he had identified which was the additional LRU checks needing to
be removed from the code.

Thanks.

- Alex

On Fri, Jul 31, 2020 at 4:55 PM Alex Shi <alex.shi@linux.alibaba.com> wrote:
>
> It looks much better than mine. and could replace 'mm/lru: introduce the relock_page_lruvec function'
> with your author signed. :)
>
> BTW,
> it's the rcu_read_lock cause the will-it-scale/page_fault3 regression which you mentained in another
> letter?
>
> Thanks
> Alex
>
> 在 2020/8/1 上午5:14, alexander.h.duyck@intel.com 写道:
> > From: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> >
> > When testing for relock we can avoid the need for RCU locking if we simply
> > compare the page pgdat and memcg pointers versus those that the lruvec is
> > holding. By doing this we can avoid the extra pointer walks and accesses of
> > the memory cgroup.
> >
> > In addition we can avoid the checks entirely if lruvec is currently NULL.
> >
> > Signed-off-by: Alexander Duyck <alexander.h.duyck@linux.intel.com>
> > ---
> >  include/linux/memcontrol.h |   52 +++++++++++++++++++++++++++-----------------
> >  1 file changed, 32 insertions(+), 20 deletions(-)
> >
> > diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> > index 6e670f991b42..7a02f00bf3de 100644
> > --- a/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -405,6 +405,22 @@ static inline struct lruvec *mem_cgroup_lruvec(struct mem_cgroup *memcg,
> >
> >  struct lruvec *mem_cgroup_page_lruvec(struct page *, struct pglist_data *);
> >
> > +static inline bool lruvec_holds_page_lru_lock(struct page *page,
> > +                                           struct lruvec *lruvec)
> > +{
> > +     pg_data_t *pgdat = page_pgdat(page);
> > +     const struct mem_cgroup *memcg;
> > +     struct mem_cgroup_per_node *mz;
> > +
> > +     if (mem_cgroup_disabled())
> > +             return lruvec == &pgdat->__lruvec;
> > +
> > +     mz = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
> > +     memcg = page->mem_cgroup ? : root_mem_cgroup;
> > +
> > +     return lruvec->pgdat == pgdat && mz->memcg == memcg;
> > +}
> > +
> >  struct mem_cgroup *mem_cgroup_from_task(struct task_struct *p);
> >
> >  struct mem_cgroup *get_mem_cgroup_from_mm(struct mm_struct *mm);
> > @@ -880,6 +896,14 @@ static inline struct lruvec *mem_cgroup_page_lruvec(struct page *page,
> >       return &pgdat->__lruvec;
> >  }
> >
> > +static inline bool lruvec_holds_page_lru_lock(struct page *page,
> > +                                           struct lruvec *lruvec)
> > +{
> > +             pg_data_t *pgdat = page_pgdat(page);
> > +
> > +             return lruvec == &pgdat->__lruvec;
> > +}
> > +
> >  static inline struct mem_cgroup *parent_mem_cgroup(struct mem_cgroup *memcg)
> >  {
> >       return NULL;
> > @@ -1317,18 +1341,12 @@ static inline void unlock_page_lruvec_irqrestore(struct lruvec *lruvec,
> >  static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
> >               struct lruvec *locked_lruvec)
> >  {
> > -     struct pglist_data *pgdat = page_pgdat(page);
> > -     bool locked;
> > +     if (locked_lruvec) {
> > +             if (lruvec_holds_page_lru_lock(page, locked_lruvec))
> > +                     return locked_lruvec;
> >
> > -     rcu_read_lock();
> > -     locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec;
> > -     rcu_read_unlock();
> > -
> > -     if (locked)
> > -             return locked_lruvec;
> > -
> > -     if (locked_lruvec)
> >               unlock_page_lruvec_irq(locked_lruvec);
> > +     }
> >
> >       return lock_page_lruvec_irq(page);
> >  }
> > @@ -1337,18 +1355,12 @@ static inline struct lruvec *relock_page_lruvec_irq(struct page *page,
> >  static inline struct lruvec *relock_page_lruvec_irqsave(struct page *page,
> >               struct lruvec *locked_lruvec, unsigned long *flags)
> >  {
> > -     struct pglist_data *pgdat = page_pgdat(page);
> > -     bool locked;
> > -
> > -     rcu_read_lock();
> > -     locked = mem_cgroup_page_lruvec(page, pgdat) == locked_lruvec;
> > -     rcu_read_unlock();
> > -
> > -     if (locked)
> > -             return locked_lruvec;
> > +     if (locked_lruvec) {
> > +             if (lruvec_holds_page_lru_lock(page, locked_lruvec))
> > +                     return locked_lruvec;
> >
> > -     if (locked_lruvec)
> >               unlock_page_lruvec_irqrestore(locked_lruvec, *flags);
> > +     }
> >
> >       return lock_page_lruvec_irqsave(page, flags);
> >  }
> >
>


  reply index

Thread overview: 63+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25 12:59 [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-25 12:59 ` [PATCH v17 01/21] mm/vmscan: remove unnecessary lruvec adding Alex Shi
2020-07-25 12:59 ` [PATCH v17 02/21] mm/page_idle: no unlikely double check for idle page counting Alex Shi
2020-07-25 12:59 ` [PATCH v17 03/21] mm/compaction: correct the comments of compact_defer_shift Alex Shi
2020-07-27 17:29   ` Alexander Duyck
2020-07-28 11:59     ` Alex Shi
2020-07-28 14:17       ` Alexander Duyck
2020-07-25 12:59 ` [PATCH v17 04/21] mm/compaction: rename compact_deferred as compact_should_defer Alex Shi
2020-07-25 12:59 ` [PATCH v17 05/21] mm/thp: move lru_add_page_tail func to huge_memory.c Alex Shi
2020-07-25 12:59 ` [PATCH v17 06/21] mm/thp: clean up lru_add_page_tail Alex Shi
2020-07-25 12:59 ` [PATCH v17 07/21] mm/thp: remove code path which never got into Alex Shi
2020-07-25 12:59 ` [PATCH v17 08/21] mm/thp: narrow lru locking Alex Shi
2020-07-25 12:59 ` [PATCH v17 09/21] mm/memcg: add debug checking in lock_page_memcg Alex Shi
2020-07-25 12:59 ` [PATCH v17 10/21] mm/swap: fold vm event PGROTATED into pagevec_move_tail_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 11/21] mm/lru: move lru_lock holding in func lru_note_cost_page Alex Shi
2020-07-25 12:59 ` [PATCH v17 12/21] mm/lru: move lock into lru_note_cost Alex Shi
2020-07-25 12:59 ` [PATCH v17 13/21] mm/lru: introduce TestClearPageLRU Alex Shi
2020-07-29  3:53   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 14/21] mm/compaction: do page isolation first in compaction Alex Shi
2020-07-25 12:59 ` [PATCH v17 15/21] mm/thp: add tail pages into lru anyway in split_huge_page() Alex Shi
2020-07-25 12:59 ` [PATCH v17 16/21] mm/swap: serialize memcg changes in pagevec_lru_move_fn Alex Shi
2020-07-25 12:59 ` [PATCH v17 17/21] mm/lru: replace pgdat lru_lock with lruvec lock Alex Shi
2020-07-27 23:34   ` Alexander Duyck
2020-07-28  7:15     ` Alex Shi
2020-07-28 11:19     ` Alex Shi
2020-07-28 14:54       ` Alexander Duyck
2020-07-29  1:00         ` Alex Shi
2020-07-29  1:27           ` Alexander Duyck
2020-07-29  2:27             ` Alex Shi
2020-07-28 15:39     ` Alex Shi
2020-07-28 15:55       ` Alexander Duyck
2020-07-29  0:48         ` Alex Shi
2020-07-29  3:54   ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 18/21] mm/lru: introduce the relock_page_lruvec function Alex Shi
2020-07-29 17:52   ` Alexander Duyck
2020-07-30  6:08     ` Alex Shi
2020-07-31 14:20       ` Alexander Duyck
2020-07-31 21:14   ` [PATCH RFC] mm: Add function for testing if the current lruvec lock is valid alexander.h.duyck
2020-07-31 23:54     ` Alex Shi
2020-08-02 18:20       ` Alexander Duyck [this message]
2020-08-04  6:13         ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 19/21] mm/vmscan: use relock for move_pages_to_lru Alex Shi
2020-08-03 22:49   ` Alexander Duyck
2020-08-04  6:23     ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 20/21] mm/pgdat: remove pgdat lru_lock Alex Shi
2020-08-03 22:42   ` Alexander Duyck
2020-08-03 22:45     ` Alexander Duyck
2020-08-04  6:22       ` Alex Shi
2020-07-25 12:59 ` [PATCH v17 21/21] mm/lru: revise the comments of lru_lock Alex Shi
2020-08-03 22:37   ` Alexander Duyck
2020-08-04 10:04     ` Alex Shi
2020-08-04 14:29       ` Alexander Duyck
2020-07-27  5:40 ` [PATCH v17 00/21] per memcg lru lock Alex Shi
2020-07-29 14:49   ` Alex Shi
2020-07-29 18:06     ` Hugh Dickins
2020-07-30  2:16       ` Alex Shi
2020-08-03 15:07         ` Michal Hocko
2020-08-04  6:14           ` Alex Shi
2020-07-31 21:31 ` Alexander Duyck
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:36 ` Alex Shi
2020-08-04  8:37 ` Alex Shi
2020-08-04  8:37 ` Alex Shi

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