linux-kernel - [PATCH] sched/fair: Fix math notation errors in avg

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Message-ID: <20260114090035.19033-1-zhanxusheng@xiaomi.com>
Date: Wed, 14 Jan 2026 17:00:35 +0800
From: Zhan Xusheng <zhanxusheng1024@...il.com>
To: Peter Zijlstra <peterz@...radead.org>
Cc: Ingo Molnar <mingo@...nel.org>,
	linux-sched@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Zhan Xusheng <zhanxusheng@...omi.com>
Subject: [PATCH] sched/fair: Fix math notation errors in avg_vruntime comment

The avg_vruntime comment contains a couple of mathematical notation
issues:

 - The summation over w_i * (V - v_i) is written in an ambiguous form
 - The delta term refers to v instead of v0, which is inconsistent
   with the code and preceding explanation

Fix these to make the comment mathematically correct and consistent
with the implementation.

Signed-off-by: Zhan Xusheng <zhanxusheng@...omi.com>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e71302282671..36c6009a0df4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -576,7 +576,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
  *
  *   \Sum lag_i = 0
  *   \Sum w_i * (V - v_i) = 0
- *   \Sum w_i * V - w_i * v_i = 0
+ *   \Sum (w_i * V - w_i * v_i) = 0
  *
  * From which we can solve an expression for V in v_i (which we have in
  * se->vruntime):
@@ -611,7 +611,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se)
  *              \Sum w_i := cfs_rq->avg_load
  *
  * Since zero_vruntime closely tracks the per-task service, these
- * deltas: (v_i - v), will be in the order of the maximal (virtual) lag
+ * deltas: (v_i - v0), will be in the order of the maximal (virtual) lag
  * induced in the system due to quantisation.
  *
  * Also, we use scale_load_down() to reduce the size.
-- 
2.43.0