From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Linux PM <linux-pm@vger.kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Christian Loehle <christian.loehle@arm.com>,
Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Subject: [PATCH v1 5/9] cpuidle: teo: Clarify two code comments
Date: Mon, 13 Jan 2025 19:41:55 +0100 [thread overview]
Message-ID: <8472971.T7Z3S40VBb@rjwysocki.net> (raw)
In-Reply-To: <6116275.lOV4Wx5bFT@rjwysocki.net>
From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Rewrite two code comments suposed to explain its behavior that are too
concise or not sufficiently clear.
No functional impact.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/cpuidle/governors/teo.c | 16 +++++++++++-----
1 file changed, 11 insertions(+), 5 deletions(-)
--- a/drivers/cpuidle/governors/teo.c
+++ b/drivers/cpuidle/governors/teo.c
@@ -154,9 +154,10 @@
if (cpu_data->time_span_ns >= cpu_data->sleep_length_ns) {
/*
- * One of the safety nets has triggered or the wakeup was close
- * enough to the closest timer event expected at the idle state
- * selection time to be discarded.
+ * This causes the wakeup to be counted as a hit regardless of
+ * regardless of the real idle duration which doesn't need to be
+ * computed because the wakeup has been close enough to an
+ * anticipated timer.
*/
measured_ns = U64_MAX;
} else {
@@ -302,8 +303,13 @@
cpu_data->time_span_ns = local_clock();
/*
- * Set the expected sleep length to infinity in case of an early
- * return.
+ * Set the sleep length to infitity in case the invocation of
+ * tick_nohz_get_sleep_length() below is skipped, in which case it won't
+ * be known whether or not the subsequent wakeup is caused by a timer.
+ * It is generally fine to count the wakeup as an intercept then, except
+ * for the cases when the CPU is mostly woken up by timers and there may
+ * be opportunities to ask for a deeper idle state when no imminent
+ * timers are scheduled which may be missed.
*/
cpu_data->sleep_length_ns = KTIME_MAX;
next prev parent reply other threads:[~2025-01-13 18:52 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-13 18:32 [PATCH v1 0/9] cpuidle: teo: Cleanups and very frequent wakeups handling update Rafael J. Wysocki
2025-01-13 18:34 ` [PATCH v1 1/9] cpuidle: teo: Rearrange idle state lookup code Rafael J. Wysocki
2025-01-15 14:21 ` Christian Loehle
2025-01-13 18:36 ` [PATCH v1 2/9] cpuidle: teo: Reorder candidate state index checks Rafael J. Wysocki
2025-01-15 14:46 ` Christian Loehle
2025-01-15 15:54 ` Rafael J. Wysocki
2025-01-15 19:20 ` Christian Loehle
2025-01-15 20:48 ` Rafael J. Wysocki
2025-01-15 21:10 ` Rafael J. Wysocki
2025-01-16 12:22 ` Rafael J. Wysocki
2025-01-16 13:26 ` Christian Loehle
2025-01-16 13:27 ` Christian Loehle
2025-01-13 18:39 ` [PATCH v1 3/9] cpuidle: teo: Combine candidate state index checks against 0 Rafael J. Wysocki
2025-01-15 19:44 ` Christian Loehle
2025-01-13 18:40 ` [PATCH v1 4/9] cpuidle: teo: Drop local variable prev_intercept_idx Rafael J. Wysocki
2025-01-15 19:46 ` Christian Loehle
2025-01-13 18:41 ` Rafael J. Wysocki [this message]
2025-01-15 19:43 ` [PATCH v1 5/9] cpuidle: teo: Clarify two code comments Christian Loehle
2025-01-13 18:45 ` [PATCH v1 6/9] cpuidle: teo: Simplify counting events used for tick management Rafael J. Wysocki
2025-01-20 11:27 ` Christian Loehle
2025-01-13 18:48 ` [PATCH v1 7/9] cpuidle: teo: Skip getting the sleep length is wakeups are very frequent Rafael J. Wysocki
2025-01-20 12:08 ` Christian Loehle
2025-01-20 16:24 ` Rafael J. Wysocki
2025-01-13 18:50 ` [PATCH v1 8/9] cpuidle: teo: Simplify handling of total events count Rafael J. Wysocki
2025-01-20 12:10 ` Christian Loehle
2025-01-13 18:51 ` [PATCH v1 9/9] cpuidle: teo: Replace time_span_ns with a flag Rafael J. Wysocki
2025-01-20 12:16 ` Christian Loehle
2025-01-20 12:42 ` Rafael J. Wysocki
2025-01-15 14:52 ` [PATCH v1 0/9] cpuidle: teo: Cleanups and very frequent wakeups handling update Christian Loehle
2025-01-20 8:17 ` Aboorva Devarajan
2025-01-20 16:26 ` Rafael J. Wysocki
2025-01-20 16:24 ` Rafael J. Wysocki
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