Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.34 as permitted sender) client-ip=23.128.96.34;
MIME-Version: 1.0
References: <20231127234600.2971029-1-nphamcs@gmail.com> <20231127234600.2971029-5-nphamcs@gmail.com>
 <20231129152509.GD135852@cmpxchg.org>
In-Reply-To: <20231129152509.GD135852@cmpxchg.org>
From:   Nhat Pham <nphamcs@gmail.com>
Date:   Wed, 29 Nov 2023 17:26:35 -0800
Message-ID: <CAKEwX=P48OwcKMyeFXDuXmUOcpx3stGfV_DwunBuXjL7EuqF1w@mail.gmail.com>
Subject: Re: [PATCH v7 4/6] mm: memcg: add per-memcg zswap writeback stat
To:     Johannes Weiner <hannes@cmpxchg.org>
Cc:     akpm@linux-foundation.org, cerasuolodomenico@gmail.com,
        yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org,
        vitaly.wool@konsulko.com, mhocko@kernel.org,
        roman.gushchin@linux.dev, shakeelb@google.com,
        muchun.song@linux.dev, chrisl@kernel.org, linux-mm@kvack.org,
        kernel-team@meta.com, linux-kernel@vger.kernel.org,
        cgroups@vger.kernel.org, linux-doc@vger.kernel.org,
        linux-kselftest@vger.kernel.org, shuah@kernel.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Wed, Nov 29, 2023 at 7:25=E2=80=AFAM Johannes Weiner <hannes@cmpxchg.org=
> wrote:
>
> On Mon, Nov 27, 2023 at 03:45:58PM -0800, Nhat Pham wrote:
> > From: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> >
> > Since zswap now writes back pages from memcg-specific LRUs, we now need=
 a
> > new stat to show writebacks count for each memcg.
> >
> > Suggested-by: Nhat Pham <nphamcs@gmail.com>
> > Signed-off-by: Domenico Cerasuolo <cerasuolodomenico@gmail.com>
> > Signed-off-by: Nhat Pham <nphamcs@gmail.com>
> > ---
> >  include/linux/vm_event_item.h | 1 +
> >  mm/memcontrol.c               | 1 +
> >  mm/vmstat.c                   | 1 +
> >  mm/zswap.c                    | 3 +++
> >  4 files changed, 6 insertions(+)
> >
> > diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_ite=
m.h
> > index d1b847502f09..f4569ad98edf 100644
> > --- a/include/linux/vm_event_item.h
> > +++ b/include/linux/vm_event_item.h
> > @@ -142,6 +142,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPO=
UT,
> >  #ifdef CONFIG_ZSWAP
> >               ZSWPIN,
> >               ZSWPOUT,
> > +             ZSWP_WB,
> >  #endif
> >  #ifdef CONFIG_X86
> >               DIRECT_MAP_LEVEL2_SPLIT,
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 8c0f3f971179..f88c8fd03689 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -703,6 +703,7 @@ static const unsigned int memcg_vm_event_stat[] =3D=
 {
> >  #if defined(CONFIG_MEMCG_KMEM) && defined(CONFIG_ZSWAP)
> >       ZSWPIN,
> >       ZSWPOUT,
> > +     ZSWP_WB,
> >  #endif
> >  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> >       THP_FAULT_ALLOC,
> > diff --git a/mm/vmstat.c b/mm/vmstat.c
> > index afa5a38fcc9c..2249f85e4a87 100644
> > --- a/mm/vmstat.c
> > +++ b/mm/vmstat.c
> > @@ -1401,6 +1401,7 @@ const char * const vmstat_text[] =3D {
> >  #ifdef CONFIG_ZSWAP
> >       "zswpin",
> >       "zswpout",
> > +     "zswp_wb",
>
> ZSWPWB and "zswpwb" would match the existing naming scheme a bit
> better.
>
> >  #endif
> >  #ifdef CONFIG_X86
> >       "direct_map_level2_splits",
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 5e397fc1f375..6a761753f979 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -754,6 +754,9 @@ static enum lru_status shrink_memcg_cb(struct list_=
head *item, struct list_lru_o
> >       }
> >       zswap_written_back_pages++;
> >
> > +     if (entry->objcg)
> > +             count_objcg_event(entry->objcg, ZSWP_WB);
> > +
>
> You need to call count_vm_event() as well, otherwise the /proc/vmstat
> counter will stay zero.

Ahh I didn't check that. I only looked at the cgroup's memory.stat
counter. I'll fix this for v8!