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AHgh+Rr4x5M29dIUcDQ+HLRr3iVeXgMdpA2fVOFEWYb/HgD9GYJ2K8jPtmEhToadx61hFkMTEMna7h4F3ZzgtCY=@vger.kernel.org X-Gm-Message-State: AOJu0YwiYwFCpUItwPznw7wuvs/+aWhuuCrOfHHXLpNIdydfoBNSRmXM /ikdcHnTb8hlz98vKLck1gU0qw/CfideGJfr65UrC68pe8NwKVKpcfwx8rqSfw7GfL9nPRCfXf1 RMIkyUxClX4JzLYpHWIGL6JzQS9io5O7LACm5HYU= X-Gm-Gg: AfdE7cnEWvd+EyS43jwNif9lovsWhnpCYGWCOX6Mr0G1TXhPTvnaSvAcMJ/a3bx/0wt YYS65GdT7gG/1CUsbCDBy3CBEveORaBKTUNVAyPMxuEgV8NsW9fetw68AjPe9dFVYY/PRYSRFSH QCXpv1bj6pmRHAMeKLLLImSsaqSfUJ/9EDfKDiokmLXPR1j76tNhN7GLGLOkHjb6Zp8g0galZ+l v85lSdxFV2Tuo3sWfnC41Gjadov8HYYfPGlB5E68YujhDnqXJKnCIqPrpCV4tSQitmWXY8= X-Received: by 2002:a05:6512:3da8:b0:5ae:bfe1:737b with SMTP id 2adb3069b0e04-5b00ad0be3emr127447e87.10.1783411462118; Tue, 07 Jul 2026 01:04:22 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20260706081218.3438762-1-richardycc@google.com> In-Reply-To: From: Richard Chang Date: Tue, 7 Jul 2026 16:04:10 +0800 X-Gm-Features: AVVi8CcT4APE5Lopda5ALe3CUB6--NPm8zfKmFrx4h6gT_quiOILmNB52Mig3aI Message-ID: Subject: Re: [PATCH] mm: vmscan: abort proactive reclaim early when freezing To: Yosry Ahmed Cc: Andrew Morton , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , David Hildenbrand , Michal Hocko , Lorenzo Stoakes , Suren Baghdasaryan , "T . J . Mercier" , Martin Liu , Minchan Kim , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi Yosry, I believe we still need the outer loop check. Otherwise, we will waste CPU cycles entering the inner loop only to bail out. On Tue, Jul 7, 2026 at 10:20=E2=80=AFAM Yosry Ahmed wrot= e: > > On Mon, Jul 06, 2026 at 08:12:18AM +0000, Richard Chang wrote: > > Proactive reclaim (via memory.reclaim or node reclaim) checks for pendi= ng > > signals in its outer loop in user_proactive_reclaim(). However, the inn= er > > reclaim loops=E2=80=94scanning cgroups in shrink_many() and evicting fo= lios in > > try_to_shrink_lruvec() can run for a long time before returning to the > > outer loop, especially on systems with many cgroups or large memory siz= es. > > > > This latency in responding to signals can block the freezer (both cgrou= p > > freezer and system suspend), leading to freezer timeouts. This issue wa= s > > specifically observed on Android when attempting to freeze background > > cgroups while proactive reclaim was active. > > > > Add a signal_pending() check to should_abort_scan() for proactive recla= im > > paths. Since should_abort_scan() is called within the inner scanning an= d > > eviction loops, this allows proactive reclaim to abort early and return= to > > the outer loop, ensuring the task can enter the refrigerator in a timel= y > > manner. > > Do we still need the check in the outer loop? > > > > > This check is limited to proactive reclaim (sc->proactive) to avoid > > affecting reactive reclaim paths, and wrapped in unlikely() as it is a > > slow path. > > > > Signed-off-by: Richard Chang > > --- > > mm/vmscan.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/mm/vmscan.c b/mm/vmscan.c > > index 35c3bb15ae96..fb472e924fc7 100644 > > --- a/mm/vmscan.c > > +++ b/mm/vmscan.c > > @@ -4929,6 +4929,9 @@ static bool should_abort_scan(struct lruvec *lruv= ec, struct scan_control *sc) > > int i; > > enum zone_watermarks mark; > > > > + if (unlikely(sc->proactive && signal_pending(current))) > > + return true; > > + > > if (sc->nr_reclaimed >=3D max(sc->nr_to_reclaim, compact_gap(sc->= order))) > > return true; > > > > -- > > 2.55.0.rc2.803.g1fd1e6609c-goog > > > >