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Mercier" Date: Thu, 12 Dec 2024 10:22:31 -0800 Message-ID: Subject: Re: [RFC PATCH] mm/mglru: keep the root_memcg reclaim behavior the same as memcg reclaim To: hailong Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuzhao@google.com, 21cnbao@gmail.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 58BEEC0008 X-Stat-Signature: xpr41pxdaa63j43r8kn5m59ycgb9cg4y X-Rspam-User: X-HE-Tag: 1734027738-69716 X-HE-Meta: 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 ZsUKMA0C bh76YpoeYtsl2ct9lPGdz+tmfcTpLEzn53r+XKXMIbxD5B0gvbGCh8rPWabIVeIDhlQKUgaVxB9HvsMff5AP6QMB+dnUMdeHWSiv3KMUUAXRiRZcfrbsddos+JA9U7V+WYe9fPOcxChpDssZ+Ad4JzG3DRrqeT8b4ldAYxWpTsJjTwlgM9k2iAQSilOgc4uHcETae0+Hd8z1l6VYrE34//iww2+m/6hC21m8MPjQy54IdubJmfL/4IiryhrXeFiBnGE+kRHG1SwS43/uuzMMxwRDnmAA8c51lGY0TMdBMOd6QLsCYs/g9f+AWZc62ZFW0G1DRvqINGhldomL7AHFBcmTdLFhNA7Rqsi9S0O7L7lIgU+XXEmocEWBJIQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.086582, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, Dec 12, 2024 at 1:57=E2=80=AFAM hailong wrot= e: > > From: Hailong Liu > > commit a579086c99ed ("mm: multi-gen LRU: remove eviction fairness safegua= rd") said > Note that memcg LRU only applies to global reclaim. For memcg reclaim, > the eviction will continue, even if it is overshooting. This becomes > unconditional due to code simplification. > > Howeven, if we reclaim a root memcg by sysfs (memory.reclaim), the behavi= or acts > as a kswapd or direct reclaim. Hi Hailong, Why do you think this is a problem? > Fix this by remove the condition of mem_cgroup_is_root in > root_reclaim(). > Signed-off-by: Hailong Liu > --- > mm/vmscan.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 76378bc257e3..1f74f3ba0999 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -216,7 +216,7 @@ static bool cgroup_reclaim(struct scan_control *sc) > */ > static bool root_reclaim(struct scan_control *sc) > { > - return !sc->target_mem_cgroup || mem_cgroup_is_root(sc->target_me= m_cgroup); > + return !sc->target_mem_cgroup; > } > > /** > -- > Actually we switch to mglru on kernel-6.1 and see different behavior on > root_mem_cgroup reclaim. so is there any background fot this? Reclaim behavior differs with MGLRU. https://lore.kernel.org/lkml/20221201223923.873696-1-yuzhao@google.com/ On even more recent kernels, regular LRU reclaim has also changed. https://lore.kernel.org/lkml/20240514202641.2821494-1-hannes@cmpxchg.org/ > Brs, > Hailong. >