linux-kernel - Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify lruvec_holds_page_lru

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Message-ID: <YHfmcLLbW6MMbcPG@dhcp22.suse.cz>
Date:   Thu, 15 Apr 2021 09:08:32 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Johannes Weiner <hannes@...xchg.org>
Cc:     Muchun Song <songmuchun@...edance.com>, guro@...com,
        akpm@...ux-foundation.org, shakeelb@...gle.com,
        vdavydov.dev@...il.com, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, duanxiongchun@...edance.com,
        fam.zheng@...edance.com
Subject: Re: [External] Re: [PATCH 4/7] mm: memcontrol: simplify
 lruvec_holds_page_lru_lock

On Wed 14-04-21 13:49:56, Johannes Weiner wrote:
> On Wed, Apr 14, 2021 at 06:00:42PM +0800, Muchun Song wrote:
> > On Wed, Apr 14, 2021 at 5:44 PM Michal Hocko <mhocko@...e.com> wrote:
> > >
> > > On Tue 13-04-21 14:51:50, Muchun Song wrote:
> > > > We already have a helper lruvec_memcg() to get the memcg from lruvec, we
> > > > do not need to do it ourselves in the lruvec_holds_page_lru_lock(). So use
> > > > lruvec_memcg() instead. And if mem_cgroup_disabled() returns false, the
> > > > page_memcg(page) (the LRU pages) cannot be NULL. So remove the odd logic
> > > > of "memcg = page_memcg(page) ? : root_mem_cgroup". And use lruvec_pgdat
> > > > to simplify the code. We can have a single definition for this function
> > > > that works for !CONFIG_MEMCG, CONFIG_MEMCG + mem_cgroup_disabled() and
> > > > CONFIG_MEMCG.
> > >
> > > Neat. While you are at it wouldn't it make sesne to rename the function
> > > as well. I do not want to bikeshed but this is really a misnomer. it
> > > doesn't check anything about locking. page_belongs_lruvec?
> > 
> > Right. lruvec_holds_page_lru_lock is used to check whether
> > the page belongs to the lruvec. page_belongs_lruvec
> > obviously more clearer. I can rename it to
> > page_belongs_lruvec the next version.
> 
> This sounds strange to me, I think 'belongs' needs a 'to' to be
> correct, so page_belongs_to_lruvec(). Still kind of a mouthful.
> 
> page_matches_lruvec()?
> 
> page_from_lruvec()?

Any of those is much better than what we have here.

-- 
Michal Hocko
SUSE Labs