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([240e:b8f:2a91:7500:c9e5:7339:1a5c:8e69]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2a2f3c9b52asm194379235ad.45.2025.12.25.22.32.41 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 25 Dec 2025 22:32:44 -0800 (PST) From: Huang Shijie To: mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org Cc: dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, linux-kernel@vger.kernel.org, vineethr@linux.ibm.com, kprateek.nayak@amd.com, cl@linux.com, Huang Shijie Subject: [PATCH v7 1/1] sched: update the rq->avg_idle when a task is moved to an idle CPU Date: Fri, 26 Dec 2025 14:32:03 +0800 Message-ID: <20251226063203.5947-2-shijie8@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251226063203.5947-1-shijie8@gmail.com> References: <20251226063203.5947-1-shijie8@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" In the newidle balance, the rq->idle_stamp may set to a non-zero value if it cannot pull any task. In the wakeup, it will detect the rq->idle_stamp, and updates the rq->avg_idle, then ends the CPU idle status by setting rq->idle_stamp to zero. Besides the wakeup, current code does not end the CPU idle status when a task is moved to the idle CPU, such as fork/clone, execve, or other cases. In order to get more accurate rq->avg_idle, we need to update it at more places(not only the wakeup). This patch introduces a helper: update_rq_avg_idle(). And uses it in put_prev_task_idle(), so it will update the rq->avg_idle when a task is moved to an idle CPU at: -- wakeup -- fork/clone -- execve -- idle balance -- other cases Signed-off-by: Huang Shijie --- kernel/sched/core.c | 27 +++++++++++++++------------ kernel/sched/idle.c | 1 + kernel/sched/sched.h | 1 + 3 files changed, 17 insertions(+), 12 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 5b17d8e3cb55..ad52f3a3c6bf 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -3609,6 +3609,21 @@ static inline void ttwu_do_wakeup(struct task_struct= *p) trace_sched_wakeup(p); } =20 +void update_rq_avg_idle(struct rq *rq) +{ + if (rq->idle_stamp) { + u64 delta =3D rq_clock(rq) - rq->idle_stamp; + u64 max =3D 2*rq->max_idle_balance_cost; + + update_avg(&rq->avg_idle, delta); + + if (rq->avg_idle > max) + rq->avg_idle =3D max; + + rq->idle_stamp =3D 0; + } +} + static void ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, struct rq_flags *rf) @@ -3644,18 +3659,6 @@ ttwu_do_activate(struct rq *rq, struct task_struct *= p, int wake_flags, p->sched_class->task_woken(rq, p); rq_repin_lock(rq, rf); } - - if (rq->idle_stamp) { - u64 delta =3D rq_clock(rq) - rq->idle_stamp; - u64 max =3D 2*rq->max_idle_balance_cost; - - update_avg(&rq->avg_idle, delta); - - if (rq->avg_idle > max) - rq->avg_idle =3D max; - - rq->idle_stamp =3D 0; - } } =20 /* diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index 65eb8f8c1a5d..aba5ad53c07d 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -460,6 +460,7 @@ static void put_prev_task_idle(struct rq *rq, struct ta= sk_struct *prev, struct t { update_curr_idle(rq); scx_update_idle(rq, false, true); + update_rq_avg_idle(rq); } =20 static void set_next_task_idle(struct rq *rq, struct task_struct *next, bo= ol first) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 3ceaa9dc9a9e..6e3dd8c975e0 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1651,6 +1651,7 @@ static inline struct cfs_rq *group_cfs_rq(struct sche= d_entity *grp) =20 #endif /* !CONFIG_FAIR_GROUP_SCHED */ =20 +extern void update_rq_avg_idle(struct rq *rq); extern void update_rq_clock(struct rq *rq); =20 /* --=20 2.43.0