Commit 553255cc authored by Zhan Xusheng's avatar Zhan Xusheng Committed by Peter Zijlstra
Browse files

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: default avatarZhan Xusheng <zhanxusheng@xiaomi.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260114090035.19033-1-zhanxusheng@xiaomi.com
parent 8d737320

kernel/sched/fair.c

+2 −2
Original line number Diff line number Diff line
@@ -613,7 +613,7 @@ 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):
@@ -648,7 +648,7 @@ static inline s64 entity_key(struct cfs_rq *cfs_rq, struct sched_entity *se) 
 *              \Sum w_i := cfs_rq->sum_weight

 *

 * 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.