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Tue, 1 Sep 2026 15:44:04 +0800 Received: from cncheex04.Hygon.cn ([fe80::1b6f:6c58:58a4:430d]) by cncheex04.Hygon.cn ([fe80::1b6f:6c58:58a4:430d%10]) with mapi id 15.02.1544.036; Tue, 1 Sep 2026 15:44:04 +0800 From: Jianyong Wu To: Peter Zijlstra CC: Ingo Molnar , Juri Lelli , Vincent Guittot , Chen Yu , Tim Chen , Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , "Shrikanth Hegde" , Phil Auld , Andrew Morton , David Hildenbrand , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "jianyong.wu@outlook.com" , Yuan Zhong , Huangsj , Fengyu Wang , Zhiwei Ying , "justin.he@arm.com" Subject: RE: [RFC PATCH v2 07/23] sched/cache: Prioritize preferred NUMA node selection over LLC selection Thread-Topic: [RFC PATCH v2 07/23] sched/cache: Prioritize preferred NUMA node selection over LLC selection Thread-Index: AQHdNiA/Gl7/wvc7qkaJjcGUBBSfi7a3o5GAgAG7IQA= Date: Tue, 1 Sep 2026 07:44:04 +0000 Message-ID: <62e8081a9432407893fb6a9a8e397d87@hygon.cn> References: <20260827122816.756234-1-wujianyong@hygon.cn> <20260827122816.756234-8-wujianyong@hygon.cn> <20260831131643.GK4120091@noisy.programming.kicks-ass.net> In-Reply-To: <20260831131643.GK4120091@noisy.programming.kicks-ass.net> Accept-Language: zh-CN, en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [172.19.20.45] Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 6785980002 X-Stat-Signature: 4eu9uh58b7gwpo7fq463t5ibuqofuekf X-HE-Tag: 1788248651-691493 X-HE-Meta: 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 4m2HS9Se 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi Peter, > -----Original Message----- > From: Peter Zijlstra > Sent: Monday, August 31, 2026 9:17 PM > To: Jianyong Wu > Cc: Ingo Molnar ; Juri Lelli ; > Vincent Guittot ; Chen Yu > ; Tim Chen ; Dietmar > Eggemann ; Steven Rostedt > ; Ben Segall ; Mel Gorman > ; Valentin Schneider ; K > Prateek Nayak ; Shrikanth Hegde > ; Phil Auld ; Andrew > Morton ; David Hildenbrand > ; linux-kernel@vger.kernel.org; linux-mm@kvack.org; > jianyong.wu@outlook.com; Yuan Zhong ; Huangsj > ; Fengyu Wang ; Zhiwei Ying > ; justin.he@arm.com > Subject: Re: [RFC PATCH v2 07/23] sched/cache: Prioritize preferred NUMA > node selection over LLC selection >=20 > On Thu, Aug 27, 2026 at 08:28:00PM +0800, Jianyong Wu wrote: >=20 > > + /* > > + * Avoid switching sc_stat.cpu too fast. The reason to choose 2X is > > + * because: > > + * 1. It is better to keep the preferred LLC stable, rather than > > + * changing it frequently and cause migrations > > + * 2. 2X means the new preferred LLC has at least 1 more busy CPU > than > > + * the old one(200% vs 100%, eg) > > + * 3. 2X is chosen based on test results, as it delivers the optimal > > + * performance gain so far. > > + * > > + * Moving to another node takes precedence over moving inside the > > + * current one, as it did when the two updates were applied in that > > + * order. > > + */ >=20 > Comments should never refer to old code that no longer exists. Comments > are for the code as it is now. If you want to expand on details of the > transition from one implementation to the next, that's what the > Changelog is for. >=20 Sorry, I'll remove the "as it did when..." part and keep the comment to the= current behavior only. Thanks Jianyong > > + if (m_a_n_occ > 2 * curr_m_a_n_occ) > > + new_cpu =3D m_a_n_cpu; > > + else if (pref_llc_cpu >=3D 0 && pref_llc_occ > 2 * curr_m_a_occ) > > + new_cpu =3D pref_llc_cpu; > > + > > + if (new_cpu >=3D 0) > > + WRITE_ONCE(mm->sc_stat.cpu, new_cpu); > > > > update_avg_scale(&mm->sc_stat.nr_running_avg, nr_running); > > free_cpumask_var(cpus); > > -- > > 2.34.1 > > > >