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[2003:dc:6f04:b700:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48e71b78f95sm23000997f8f.28.2026.11.03.03.37.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Nov 2026 03:37:28 -0800 (PST) From: Max Kellermann To: akpm@linux-foundation.org, kasong@tencent.com, qi.zheng@linux.dev, shakeel.butt@linux.dev, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, baoquan.he@linux.dev, baolin.wang@linux.alibaba.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, hannes@cmpxchg.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org Cc: Max Kellermann Subject: [PATCH v2 5/5] mm/mglru: reschedule between memcg reclaim attempts Date: Tue, 3 Nov 2026 12:37:10 +0100 Message-ID: <20261103113711.1832834-6-max.kellermann@ionos.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20261103113711.1832834-1-max.kellermann@ionos.com> References: <20261103113711.1832834-1-max.kellermann@ionos.com> X-Mailing-List: rcu@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit shrink_one() can return immediately for empty or protected memcgs, and try_to_shrink_lruvec() can break out before reaching its cond_resched(). A scan through many memcgs can repeatedly rotate entries without giving other runnable tasks a scheduling opportunity. Call cond_resched_tasks_rcu_qs() (as the existing shrink_lruvec() loop does) after shrink_one(), while the memcg reference still pins the cursor and before reacquiring the RCU read lock. Also call it between bins and nulls-marker retries, covering scans that skip every entry. Signed-off-by: Max Kellermann --- mm/vmscan.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index 899f756bd15b..5dc5e698e243 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -5395,6 +5395,9 @@ static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) gen = get_memcg_gen(READ_ONCE(pgdat->memcg_lru.seq)); bin = first_bin = get_random_u32_below(MEMCG_NR_BINS); restart: + /* Yield between bins/retries that contain only skipped entries. */ + cond_resched_tasks_rcu_qs(); + op = 0; memcg = NULL; @@ -5425,6 +5428,14 @@ static void shrink_many(struct pglist_data *pgdat, struct scan_control *sc) op = shrink_one(lruvec, sc); + /* + * Empty or protected memcgs can bypass the + * rescheduling points in page reclaim. The memcg + * reference pins our cursor while we yield outside + * the RCU read-side critical section. + */ + cond_resched_tasks_rcu_qs(); + rcu_read_lock(); if (should_abort_scan(lruvec, sc)) -- 2.53.0