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Wed, 25 Mar 2026 22:04:42 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Thu, 26 Mar 2026 13:04:31 +0800 X-Gm-Features: AQROBzD5-fyVXx6FhxasuX11GkG5ohrgg-o9DOJ5V-xnCF8ZHhi76mmqPfSKwXM Message-ID: Subject: Re: [RFC PATCH] mm: vmscan: fix dirty folios throttling on cgroup v1 for MGLRU To: Baolin Wang Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, kasong@tencent.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 38362140002 X-Stat-Signature: i88exnfhnbeqnt6rudnp1kswhxjiupf8 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1774501484-461361 X-HE-Meta: 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 1QAnuvyy GN1Qo6zfA+vVJe3hPQb/s8txin8tHWiw8XOqz1D+WVfOhHaOIJ5QmI69CQccLfbqLdssMGBoCAI7/eWBJyR8CRVGmbeQBw87JQx/ShKHnqvMPkAy+ii72jBZWzQN7jUUJCqxN09WbyulF5qFFogchh8QF/U9fe0pMdzNWA0dozq5C/PV+nkgGQynNDPO98G9dQ0yNSsO3xpuARMdI+HwVvf0Gq0XqAP4gO3adIZPGRPUR9KVETzcuuKMBEs+SYum0Nc2N7XLwp+tl79oDoBK+d5IE5yfLpQeixDVlJfH186dKFruTVr0W1cfIGWu9M5HYV81FXGxcGtWoVyDa8KwKlrWNb7Xodllyv3ubhiA0iPYg0MLhu1M5+fLhEeQp4UPp6Qw1Qr5zFiyscRWKSnvFnaxNFIKiuUaHMI/RTMAXQzSnxumaHJPQyOvLL8iUZu7jLEfi Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 25, 2026 at 7:51=E2=80=AFPM Baolin Wang wrote: > > The balance_dirty_pages() won't do the dirty folios throttling on cgroupv= 1. > See commit 9badce000e2c ("cgroup, writeback: don't enable cgroup writebac= k > on traditional hierarchies"). > > Moreover, after commit 6b0dfabb3555 ("fs: Remove aops->writepage"), we no > longer attempt to write back filesystem folios through reclaim. > > On large memory systems, the flusher may not be able to write back quickl= y > enough. Consequently, MGLRU will encounter many folios that are already > under writeback. Since we cannot reclaim these dirty folios, the system > may run out of memory and trigger the OOM killer. > > Hence, for cgroup v1, let's throttle reclaim after waking up the flusher, > which is similar to commit 81a70c21d917 ("mm/cgroup/reclaim: fix dirty > pages throttling on cgroup v1"), to avoid unnecessary OOM. > > The following test program can easily reproduce the OOM issue. With this = patch > applied, the test passes successfully. > > $mkdir /sys/fs/cgroup/memory/test > $echo 256M > /sys/fs/cgroup/memory/test/memory.limit_in_bytes > $echo $$ > /sys/fs/cgroup/memory/test/cgroup.procs > $dd if=3D/dev/zero of=3D/mnt/data.bin bs=3D1M count=3D800 > > Signed-off-by: Baolin Wang LGTM, Reviewed-by: Barry Song Maybe we can extract a common inline helper to avoid the copy-paste duplica= tion. > --- > mm/vmscan.c | 13 ++++++++++++- > 1 file changed, 12 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 33287ba4a500..a9648269fae8 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -5036,9 +5036,20 @@ static bool try_to_shrink_lruvec(struct lruvec *lr= uvec, struct scan_control *sc) > * If too many file cache in the coldest generation can't be evic= ted > * due to being dirty, wake up the flusher. > */ > - if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty =3D=3D sc->nr.= file_taken) > + if (sc->nr.unqueued_dirty && sc->nr.unqueued_dirty =3D=3D sc->nr.= file_taken) { > + struct pglist_data *pgdat =3D lruvec_pgdat(lruvec); > + > wakeup_flusher_threads(WB_REASON_VMSCAN); > > + /* > + * For cgroupv1 dirty throttling is achieved by waking up > + * the kernel flusher here and later waiting on folios > + * which are in writeback to finish (see shrink_folio_lis= t()). > + */ > + if (!writeback_throttling_sane(sc)) > + reclaim_throttle(pgdat, VMSCAN_THROTTLE_WRITEBACK= ); > + } > + > /* whether this lruvec should be rotated */ > return nr_to_scan < 0; > } > -- > 2.47.3 >