From: Shakeel Butt <shakeelb@google.com>
To: Muchun Song <songmuchun@bytedance.com>
Cc: Roman Gushchin <guro@fb.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Linux MM <linux-mm@kvack.org>,
Xiongchun duan <duanxiongchun@bytedance.com>
Subject: Re: [External] Re: [PATCH v4 4/5] mm: memcontrol: use obj_cgroup APIs to charge kmem pages
Date: Fri, 19 Mar 2021 06:59:13 -0700 [thread overview]
Message-ID: <CALvZod5H-hL8myH1hy6YRis5vGT5JSYTQv5AeM0zagymCg0mcA@mail.gmail.com> (raw)
In-Reply-To: <CAMZfGtXSW8gX99SzYf7ourM5ZpsWYjWtiBL0MYpJXZeKB4HWXg@mail.gmail.com>
On Thu, Mar 18, 2021 at 9:05 PM Muchun Song <songmuchun@bytedance.com> wrote:
>
> On Fri, Mar 19, 2021 at 11:40 AM Shakeel Butt <shakeelb@google.com> wrote:
> >
> > On Thu, Mar 18, 2021 at 4:08 AM Muchun Song <songmuchun@bytedance.com> wrote:
> > >
> > [...]
> > >
> > > +static inline struct mem_cgroup *get_obj_cgroup_memcg(struct obj_cgroup *objcg)
> >
> > I would prefer get_mem_cgroup_from_objcg().
>
> Inspired by obj_cgroup_memcg() which returns the memcg from objcg.
> So I introduce get_obj_cgroup_memcg() which obtains a reference of
> memcg on the basis of obj_cgroup_memcg().
>
> So that the names are more consistent. Just my thought.
>
> So should I rename it to get_mem_cgroup_from_objcg?
>
If you look at other functions which get reference on mem_cgroup, they
have the format of get_mem_cgroup_*. Similarly the current function to
get a reference on obj_cgroup is get_obj_cgroup_from_current().
So, from the name get_obj_cgroup_memcg(), it seems like we are getting
reference on obj_cgroup but the function is getting reference on
mem_cgroup.
> >
> > > +{
> > > + struct mem_cgroup *memcg;
> > > +
> > > + rcu_read_lock();
> > > +retry:
> > > + memcg = obj_cgroup_memcg(objcg);
> > > + if (unlikely(!css_tryget(&memcg->css)))
> > > + goto retry;
> > > + rcu_read_unlock();
> > > +
> > > + return memcg;
> > > +}
> > > +
> > > #ifdef CONFIG_MEMCG_KMEM
> > > int memcg_alloc_page_obj_cgroups(struct page *page, struct kmem_cache *s,
> > > gfp_t gfp, bool new_page)
> > > @@ -3070,15 +3088,8 @@ static int obj_cgroup_charge_pages(struct obj_cgroup *objcg, gfp_t gfp,
> > > struct mem_cgroup *memcg;
> > > int ret;
> > >
> > > - rcu_read_lock();
> > > -retry:
> > > - memcg = obj_cgroup_memcg(objcg);
> > > - if (unlikely(!css_tryget(&memcg->css)))
> > > - goto retry;
> > > - rcu_read_unlock();
> > > -
> > > + memcg = get_obj_cgroup_memcg(objcg);
> > > ret = __memcg_kmem_charge(memcg, gfp, nr_pages);
> >
> > Why not manually inline __memcg_kmem_charge() here? This is the only user.
> >
> > Similarly manually inline __memcg_kmem_uncharge() into
> > obj_cgroup_uncharge_pages() and call obj_cgroup_uncharge_pages() in
> > obj_cgroup_release().
>
> Good point. I will do this.
>
> >
> > > -
> > > css_put(&memcg->css);
> > >
> > > return ret;
> > > @@ -3143,18 +3154,18 @@ static void __memcg_kmem_uncharge(struct mem_cgroup *memcg, unsigned int nr_page
> > > */
> > > int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
> > > {
> > > - struct mem_cgroup *memcg;
> > > + struct obj_cgroup *objcg;
> > > int ret = 0;
> > >
> > > - memcg = get_mem_cgroup_from_current();
> >
> > This was the only use of get_mem_cgroup_from_current(). Why not remove it?
>
> I saw a potential user.
>
> [PATCH v10 0/3] Charge loop device i/o to issuing cgroup
>
> To avoid reintroducing them. So I did not remove it.
>
Don't worry about that. Most probably that user would be changing this
function, so it would to better to introduce from scratch.
next prev parent reply other threads:[~2021-03-19 13:59 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-18 11:06 [PATCH v4 0/5] Use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-18 11:06 ` [PATCH v4 1/5] mm: memcontrol: introduce obj_cgroup_{un}charge_pages Muchun Song
2021-03-18 11:06 ` [PATCH v4 2/5] mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c Muchun Song
2021-03-18 15:09 ` Johannes Weiner
2021-03-19 1:00 ` Shakeel Butt
2021-03-18 11:06 ` [PATCH v4 3/5] mm: memcontrol: change ug->dummy_page only if memcg changed Muchun Song
2021-03-18 15:11 ` Johannes Weiner
2021-03-19 1:22 ` Shakeel Butt
2021-03-18 11:06 ` [PATCH v4 4/5] mm: memcontrol: use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-18 15:23 ` Johannes Weiner
2021-03-19 3:39 ` Shakeel Butt
2021-03-19 4:05 ` [External] " Muchun Song
2021-03-19 13:59 ` Shakeel Butt [this message]
2021-03-19 15:45 ` Muchun Song
2021-03-18 11:06 ` [PATCH v4 5/5] mm: memcontrol: move PageMemcgKmem to the scope of CONFIG_MEMCG_KMEM Muchun Song
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