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Wed, 2 Sep 2026 15:11:49 +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; Wed, 2 Sep 2026 15:11:49 +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 02/23] sched/topology: Introduce a NUMA distance matrix with unique distance values Thread-Topic: [RFC PATCH v2 02/23] sched/topology: Introduce a NUMA distance matrix with unique distance values Thread-Index: AQHdNiA3jheQVPdvikWpN4gB9aTKG7a46tIAgAH5vHA= Date: Wed, 2 Sep 2026 07:11:49 +0000 Message-ID: References: <20260827122816.756234-1-wujianyong@hygon.cn> <20260827122816.756234-3-wujianyong@hygon.cn> <20260901084800.GI4121339@noisy.programming.kicks-ass.net> In-Reply-To: <20260901084800.GI4121339@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: rspam07 X-Rspamd-Queue-Id: 5445F40002 X-Stat-Signature: tymxs6op4j9nz5wmn3rhzwfttym586cz X-HE-Tag: 1788333114-125748 X-HE-Meta: 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 QUP5JUYq 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > -----Original Message----- > From: Peter Zijlstra > Sent: Tuesday, September 1, 2026 4:48 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 02/23] sched/topology: Introduce a NUMA > distance matrix with unique distance values >=20 > On Thu, Aug 27, 2026 at 08:27:55PM +0800, Jianyong Wu wrote: > > Builds a refined node distance matrix based on the raw NUMA distance > matrix > > provided by BIOS. The refined matrix preserves the relative ordering of > > NUMA distances, while assigning distinct distance values to node pairs > that > > originally shared identical distances within each matrix row. This matr= ix > > is exclusively used for cache-aware scheduling and has no impact on > existing > > NUMA topology logic such as sched domain construction. > > > > For example, consider a system with 4 NUMA nodes. The raw > BIOS-provided > > distance matrix may look like this: > > > > NODE0 NODE1 NODE2 NODE3 > > NODE0 10 20 20 30 > > NODE1 20 10 20 25 > > NODE2 20 20 10 20 > > NODE3 30 25 20 10 > > > > Multiple duplicate distance values exist within each row. After the > > deduplication step, the refined distance matrix becomes: > > > > NODE0 NODE1 NODE2 NODE3 > > NODE0 10 15 20 30 > > NODE1 15 10 12 25 > > NODE2 20 12 10 15 > > NODE3 30 25 15 10 > > > > All entries in each row are now unique, while adhering to two core > principles: > > 1. The relative distance ordering from the original matrix is preserved= . > > For instance, original distance(NODE0, NODE1) < distance(NODE0, > NODE3), > > and this relative relationship is retained in the refined matrix as > well. > > 2. The matrix remains symmetric across its main diagonal. Maintaining > > symmetry is critical to guarantee consistent pairwise node distances= . > > > > Each row of this refined NUMA distance matrix is sorted in ascending > order to > > generate a unique per-node affinity sequence. This sequence will guide > > thread migration logic introduced in subsequent patches. >=20 > Hmm, I wonder if __build_all_zonelists() wants to use this, rather than > the unmodified distance table. This would ensure the node fallback order > is distinct between nodes. >=20 That is an interesting thought. Before building this node distance matrix, = I tried to reuse the zonelist fallback node matrix. But I dropped this idea w= hen I found that that matrix is not symmetric. After searching the code, I find that build_all_zonelists is initialized mu= ch earlier than sched domain. So, it seems it's not easy to let the zonelists use this= refined node distance. Thanks Jianyong