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[2001:b011:2006:1fb9:8409:195:705e:5b47]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3a49c1afb23sm284314a91.16.2026.09.28.12.15.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Sep 2026 12:15:35 -0700 (PDT) From: Yiwei Lin To: Peter Zijlstra Cc: Yiwei Lin , Andrew Morton , Ingo Molnar , Juri Lelli , Vincent Guittot , Davidlohr Bueso , Jonathan Corbet , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] rbtree: update augmented data on the way down in rb_add_augmented_cached() Date: Tue, 29 Sep 2026 03:15:26 +0800 Message-Id: <20260928191526.645160-1-s921975628@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260928140513.GF4121620@noisy.programming.kicks-ass.net> References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit On 2026/09/28 22:05, Peter Zijlstra wrote: > > And that is *very* close to being generalizable, obviating the need for > > RBCOMPUTE. Does your LLM see a way to make that happen? > > Perhaps by doing something like so? [...] > #define RB_DECLARE_CALLBACKS_MULTI(RBSTATIC, RBNAME, \ > - RBSTRUCT, RBFIELD, RBCOPY, RBCOMPUTE) \ > + RBSTRUCT, RBFIELD, RBCOMPUTE, RBAUG...) \ Yes, and since RBCOMPUTE is always "reset the fields to the node's own contribution, then fold in each child". I think we can also generalize it with RBMERGE, by adding one extra RBINIT: static inline void min_vruntime_init(struct sched_entity *se) { se->min_vruntime = se->vruntime; se->min_slice = se->slice; se->max_slice = se->slice; } So the original RBCOMPUTE can be generated by the template instead, which allow us to remove min_vruntime_update. static inline bool RBNAME ## _compute(RBSTRUCT *node) \ { \ typeof(node->RBAUGMENTED) aug; \ RBSTRUCT *child; \ \ RBINIT(node, &aug); \ if (node->RBFIELD.rb_left) { \ child = rb_entry(node->RBFIELD.rb_left, RBSTRUCT, RBFIELD); \ RBMERGE(&aug, &child->RBAUGMENTED); \ } \ if (node->RBFIELD.rb_right) { \ child = rb_entry(node->RBFIELD.rb_right, RBSTRUCT, RBFIELD); \ RBMERGE(&aug, &child->RBAUGMENTED); \ } \ if (!memcmp(&aug, &node->RBAUGMENTED, sizeof(aug))) \ return true; \ node->RBAUGMENTED = aug; \ return false; \ } \ Base on this I have another idea: can we let augmented data becomes one member and init/merge just work on its type by value. Taking sched for example: struct_group_tagged(sched_aug, aug, u64 min_vruntime; u64 min_slice; u64 max_slice; ); So fair.c's se->min_vruntime etc. can stay as they are, we don't have to rely on the FOR_EACH machinery. Do you think this can be better or do you prefer the field-list form? Thanks, Yiwei Lin