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([2601:188:c100:5710:315f:57b3:b997:5fca]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7c55e15e86csm187003085a.48.2025.03.11.10.42.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 11 Mar 2025 10:42:54 -0700 (PDT) From: Waiman Long X-Google-Original-From: Waiman Long Message-ID: <825fb8bc-91ca-4de4-9c8d-44590b6c1cba@redhat.com> Date: Tue, 11 Mar 2025 13:42:53 -0400 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] sched/numa: skip VMA scanning on memory pinned to one NUMA node via cpuset.mems To: Libo Chen , peterz@infradead.org, mgorman@techsingularity.net Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, tj@kernel.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com References: <20250311160447.2813222-1-libo.chen@oracle.com> Content-Language: en-US In-Reply-To: <20250311160447.2813222-1-libo.chen@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 3/11/25 12:04 PM, Libo Chen wrote: > When the memory of the current task is pinned to one NUMA node by cgroup, > there is no point in continuing the rest of VMA scanning and hinting page > faults as they will just be overhead. With this change, there will be no > more unnecessary PTE updates or page faults in this scenario. > > Signed-off-by: Libo Chen > --- > kernel/sched/fair.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index c798d27952431..ec4749a7be33a 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3315,6 +3315,13 @@ static void task_numa_work(struct callback_head *work) > if (p->flags & PF_EXITING) > return; > > + /* > + * Memory is pinned to only one NUMA node via cpuset.mems, naturally > + * no page can be migrated. > + */ > + if (nodes_weight(cpuset_current_mems_allowed) == 1) > + return; > + > if (!mm->numa_next_scan) { > mm->numa_next_scan = now + > msecs_to_jiffies(sysctl_numa_balancing_scan_delay); Do you have any performance improvement data that can be included in the commit log? Cheers, Longman