From: Muchun Song <songmuchun@bytedance.com>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Roman Gushchin <guro@fb.com>, 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>
Subject: Re: [External] Re: [PATCH v3 3/4] mm: memcontrol: use obj_cgroup APIs to charge kmem pages
Date: Sat, 13 Mar 2021 00:46:11 +0800 [thread overview]
Message-ID: <CAMZfGtWQ2HrV2Sw8K_vBJ5c9U+V2Q7AOha9aV6fR3RwrtbPZvA@mail.gmail.com> (raw)
In-Reply-To: <YEuPydlPkq87TO5H@cmpxchg.org>
On Fri, Mar 12, 2021 at 11:59 PM Johannes Weiner <hannes@cmpxchg.org> wrote:
>
> On Fri, Mar 12, 2021 at 05:22:55PM +0800, Muchun Song wrote:
> > On Thu, Mar 11, 2021 at 6:05 AM Johannes Weiner <hannes@cmpxchg.org> wrote:
> > > > @@ -6828,7 +6857,7 @@ static void uncharge_batch(const struct uncharge_gather *ug)
> > > >
> > > > static void uncharge_page(struct page *page, struct uncharge_gather *ug)
> > > > {
> > > > - unsigned long nr_pages;
> > > > + unsigned long nr_pages, nr_kmem;
> > > > struct mem_cgroup *memcg;
> > > >
> > > > VM_BUG_ON_PAGE(PageLRU(page), page);
> > > > @@ -6836,34 +6865,44 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
> > > > if (!page_memcg_charged(page))
> > > > return;
> > > >
> > > > + nr_pages = compound_nr(page);
> > > > /*
> > > > * Nobody should be changing or seriously looking at
> > > > - * page memcg at this point, we have fully exclusive
> > > > - * access to the page.
> > > > + * page memcg or objcg at this point, we have fully
> > > > + * exclusive access to the page.
> > > > */
> > > > - memcg = page_memcg_check(page);
> > > > + if (PageMemcgKmem(page)) {
> > > > + struct obj_cgroup *objcg;
> > > > +
> > > > + objcg = page_objcg(page);
> > > > + memcg = obj_cgroup_memcg_get(objcg);
> > > > +
> > > > + page->memcg_data = 0;
> > > > + obj_cgroup_put(objcg);
> > > > + nr_kmem = nr_pages;
> > > > + } else {
> > > > + memcg = page_memcg(page);
> > > > + page->memcg_data = 0;
> > > > + nr_kmem = 0;
> > > > + }
> > >
> > > Why is all this moved above the uncharge_batch() call?
> >
> > Before calling obj_cgroup_put(), we need set page->memcg_data
> > to zero. So I move "page->memcg_data = 0" to here.
>
> Yeah, it makes sense to keep those together, but we can move them both
> down to after the uncharge, right?
Right. I am doing this.
>
> > > It separates the pointer manipulations from the refcounting, which
> > > makes the code very difficult to follow.
> > >
> > > > +
> > > > if (ug->memcg != memcg) {
> > > > if (ug->memcg) {
> > > > uncharge_batch(ug);
> > > > uncharge_gather_clear(ug);
> > > > }
> > > > ug->memcg = memcg;
> > > > + ug->dummy_page = page;
> > >
> > > Why this change?
> >
> > Just like ug->memcg, we do not need to set
> > ug->dummy_page in every loop.
>
> Ah, okay. That's a reasonable change, it's just confusing because I
> thought this was a requirement for the new code to work. But I didn't
> see how it relied on that, and it made me think I'm not understanding
> your code ;) It's better to split that into a separate patch.
Sorry for confusing you. I will split that into a separate patch.
Thanks.
>
> > I will rework the code in the next version.
>
> Thanks!
next prev parent reply other threads:[~2021-03-12 16:47 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-09 10:07 [PATCH v3 0/4] Use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-09 10:07 ` [PATCH v3 1/4] mm: memcontrol: introduce obj_cgroup_{un}charge_pages Muchun Song
2021-03-11 12:30 ` Johannes Weiner
2021-03-11 18:56 ` Shakeel Butt
2021-03-09 10:07 ` [PATCH v3 2/4] mm: memcontrol: make page_memcg{_rcu} only applicable for non-kmem page Muchun Song
2021-03-10 19:57 ` Roman Gushchin
2021-03-11 6:45 ` [External] " Muchun Song
2021-03-11 13:12 ` Johannes Weiner
2021-03-12 7:14 ` [External] " Muchun Song
2021-03-12 19:23 ` Johannes Weiner
2021-03-12 22:42 ` Shakeel Butt
2021-03-12 23:07 ` Johannes Weiner
2021-03-12 23:18 ` Shakeel Butt
2021-03-14 13:56 ` Muchun Song
2021-03-12 3:22 ` Shakeel Butt
2021-03-12 5:02 ` [External] " Muchun Song
2021-03-09 10:07 ` [PATCH v3 3/4] mm: memcontrol: use obj_cgroup APIs to charge kmem pages Muchun Song
2021-03-10 19:53 ` Roman Gushchin
2021-03-11 6:50 ` [External] " Muchun Song
2021-03-10 22:05 ` Johannes Weiner
2021-03-12 9:22 ` [External] " Muchun Song
2021-03-12 15:59 ` Johannes Weiner
2021-03-12 16:46 ` Muchun Song [this message]
2021-03-11 17:48 ` kernel test robot
2021-03-09 10:07 ` [PATCH v3 4/4] mm: memcontrol: move PageMemcgKmem to the scope of CONFIG_MEMCG_KMEM Muchun Song
2021-03-10 19:30 ` Roman Gushchin
2021-03-12 3:26 ` Shakeel Butt
2021-03-12 19:24 ` Johannes Weiner
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