Re: [External] Re: [RFC PATCH v3 02/12] mm: memcontrol: introduce compact_lock_page_lruvec_irqsave

From: Muchun Song <songmuchun@bytedance.com>
To: Roman Gushchin <guro@fb.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
	Michal Hocko <mhocko@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Shakeel Butt <shakeelb@google.com>,
	Vladimir Davydov <vdavydov.dev@gmail.com>,
	LKML <linux-kernel@vger.kernel.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	Xiongchun duan <duanxiongchun@bytedance.com>,
	fam.zheng@bytedance.com, "Singh, Balbir" <bsingharora@gmail.com>,
	Yang Shi <shy828301@gmail.com>,
	Alex Shi <alex.shi@linux.alibaba.com>
Subject: Re: [External] Re: [RFC PATCH v3 02/12] mm: memcontrol: introduce compact_lock_page_lruvec_irqsave
Date: Wed, 26 May 2021 10:49:08 +0800	[thread overview]
Message-ID: <CAMZfGtXEJv1mU5CHZV3H7Qkkmq0mEugQpOpDM7Q=K-Sr1L3ydQ@mail.gmail.com> (raw)
In-Reply-To: <YK0yBhDj+9zJlz/d@carbon.dhcp.thefacebook.com>

On Wed, May 26, 2021 at 1:21 AM Roman Gushchin <guro@fb.com> wrote:
>
> On Wed, Apr 21, 2021 at 03:00:49PM +0800, Muchun Song wrote:
> > If we reuse the objcg APIs to charge LRU pages, the page_memcg()
> > can be changed when the LRU pages reparented. In this case, we need
> > to acquire the new lruvec lock.
> >
> >     lruvec = mem_cgroup_page_lruvec(page);
> >
> >     // The page is reparented.
> >
> >     compact_lock_irqsave(&lruvec->lru_lock, &flags, cc);
> >
> >     // Acquired the wrong lruvec lock and need to retry.
> >
> > But compact_lock_irqsave() only take lruvec lock as the parameter,
> > we cannot aware this change. If it can take the page as parameter
> > to acquire the lruvec lock. When the page memcg is changed, we can
> > use the page_memcg() detect whether we need to reacquire the new
> > lruvec lock. So compact_lock_irqsave() is not suitable for us.
> > Similar to lock_page_lruvec_irqsave(), introduce
> > compact_lock_page_lruvec_irqsave() to acquire the lruvec lock in
> > the compaction routine.
> >
> > Signed-off-by: Muchun Song <songmuchun@bytedance.com>
>
> Acked-by: Roman Gushchin <guro@fb.com>

Thanks.

>
> > ---
> >  mm/compaction.c | 27 ++++++++++++++++++++++++---
> >  1 file changed, 24 insertions(+), 3 deletions(-)
> >
> > diff --git a/mm/compaction.c b/mm/compaction.c
> > index 1c500e697c88..082293587cc6 100644
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -511,6 +511,29 @@ static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags,
> >       return true;
> >  }
> >
> > +static struct lruvec *
> > +compact_lock_page_lruvec_irqsave(struct page *page, unsigned long *flags,
> > +                              struct compact_control *cc)
>
> Maybe compact_lock_page_irqsave() to make it more similar to
> compact_lock_irqsafe()? But it's up to you.

I like a more brief name, compact_lock_page_irqsave is a good and
brief name. Thanks.

>
> Thanks!