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[34.121.121.222]) by smtp.gmail.com with ESMTPSA id 8926c6da1cb9f-4de5f8e41easm918119173.136.2024.11.08.09.48.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 08 Nov 2024 09:48:48 -0800 (PST) From: "Joel Fernandes (Google)" To: linux-kernel@vger.kernel.org, Anna-Maria Behnsen , Frederic Weisbecker , Ingo Molnar , Thomas Gleixner Cc: "Joel Fernandes (Google)" Subject: [RFC 1/3] tick-sched: Remove last_tick and calculate next tick from now Date: Fri, 8 Nov 2024 17:48:34 +0000 Message-ID: <20241108174839.1016424-2-joel@joelfernandes.org> X-Mailer: git-send-email 2.47.0.277.g8800431eea-goog In-Reply-To: <20241108174839.1016424-1-joel@joelfernandes.org> References: <20241108174839.1016424-1-joel@joelfernandes.org> 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" During tick restart, we use last_tick and forward it past now. Since we are forwarding past now, we can simply use now as a reference instead of last_tick. This patch removes last_tick and does so. This patch potentially does more mul/imul than the existing code, as sometimes forwarding past now need not be done if last_tick > now. However, the patch is a cleanup which reduces LOC and reduces the size of struct tick_sched. Signed-off-by: Joel Fernandes (Google) --- kernel/time/tick-sched.c | 7 ++----- kernel/time/tick-sched.h | 1 - kernel/time/timer_list.c | 1 - 3 files changed, 2 insertions(+), 7 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 71a792cd8936..52a4eda664cf 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -837,11 +837,9 @@ EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us); =20 static void tick_nohz_restart(struct tick_sched *ts, ktime_t now) { + /* Set the time to expire on the next tick and not some far away future. = */ hrtimer_cancel(&ts->sched_timer); - hrtimer_set_expires(&ts->sched_timer, ts->last_tick); - - /* Forward the time to expire in the future */ - hrtimer_forward(&ts->sched_timer, now, TICK_NSEC); + hrtimer_set_expires(&ts->sched_timer, DIV_ROUND_UP_ULL(now, TICK_NSEC) * = TICK_NSEC); =20 if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) { hrtimer_start_expires(&ts->sched_timer, @@ -1043,7 +1041,6 @@ static void tick_nohz_stop_tick(struct tick_sched *ts= , int cpu) calc_load_nohz_start(); quiet_vmstat(); =20 - ts->last_tick =3D hrtimer_get_expires(&ts->sched_timer); tick_sched_flag_set(ts, TS_FLAG_STOPPED); trace_tick_stop(1, TICK_DEP_MASK_NONE); } diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h index b4a7822f495d..7210cc473855 100644 --- a/kernel/time/tick-sched.h +++ b/kernel/time/tick-sched.h @@ -71,7 +71,6 @@ struct tick_sched { =20 /* Tick handling */ struct hrtimer sched_timer; - ktime_t last_tick; ktime_t next_tick; unsigned long idle_jiffies; ktime_t idle_waketime; diff --git a/kernel/time/timer_list.c b/kernel/time/timer_list.c index 1c311c46da50..26688a3b8ea8 100644 --- a/kernel/time/timer_list.c +++ b/kernel/time/timer_list.c @@ -154,7 +154,6 @@ static void print_cpu(struct seq_file *m, int cpu, u64 = now) struct tick_sched *ts =3D tick_get_tick_sched(cpu); P_flag(nohz, TS_FLAG_NOHZ); P_flag(highres, TS_FLAG_HIGHRES); - P_ns(last_tick); P_flag(tick_stopped, TS_FLAG_STOPPED); P(idle_jiffies); P(idle_calls); --=20 2.47.0.277.g8800431eea-goog