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Mon, 02 Mar 2026 01:48:01 -0800 (PST) MIME-Version: 1.0 References: <20260228161008.707-1-lenohou@gmail.com> <20260228212837.59661-1-21cnbao@gmail.com> In-Reply-To: From: Kairui Song Date: Mon, 2 Mar 2026 17:47:24 +0800 X-Gm-Features: AaiRm52oYsG1VpW4_A-4yy9TFAxWeWKKbmV-EF2sBBxf3bsGB5wJs_psGbGDYmA Message-ID: Subject: Re: [PATCH] mm/mglru: fix cgroup OOM during MGLRU state switching To: Barry Song <21cnbao@gmail.com>, Yafang Shao Cc: bingfangguo@tencent.com, lenohou@gmail.com, akpm@linux-foundation.org, axelrasmussen@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, weixugc@google.com, wjl.linux@gmail.com, yuanchu@google.com, yuzhao@google.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E89D98000A X-Stat-Signature: xi3ajo919mjaks7pfhbzj75nujhbf1pm X-Rspam-User: X-HE-Tag: 1772444882-206369 X-HE-Meta: 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 axD4g+py 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 2, 2026 at 5:20=E2=80=AFPM Barry Song <21cnbao@gmail.com> wrote= : > > On Mon, Mar 2, 2026 at 4:25=E2=80=AFPM Yafang Shao = wrote: > > > > The challenge we're currently facing is that we don't yet know which > > workloads would benefit from it ;) > > We do want to enable mglru on our production servers, but first we > > need to address the risk of OOM during the switch=E2=80=94that's exactl= y why > > we're proposing this patch. > > Nobody objects to your intention to fix it. I=E2=80=99m curious: to what > extent do we want to fix it? Do we aim to merely reduce the probability > of OOM and other mistakes, or do we want a complete fix that makes > the dynamic on/off fully safe? Yeah, I'm glad that more people are trying MGLRU and improving it. We also have an downstream fix for the OOM on switch issue, but that's mostly as a fallback in case MGLRU doesn't work well, our goal is still try to enable MGLRU as much as possible, many issues have been identified and I'm willing to push and fix things upstream together. I didn't consider the the OOM on switch an upstream issue though. But to fix that we just used a schedule_timeout when seeing the lru status is different from the global status, very close to what Barry suggested, with some other tweaks. Keep doing the reclaim during the switch did result in some unexpected behaviors, including OOM still occurring, just much more unlikely than before. Like a typical TOCTOU problem for checking the lru's status. Let me Cc BIngfang, maybe he can provide more detail.