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Message-ID: <Y+O9gjj/ZJY/Qnoo@lothringen>
Date: Wed, 8 Feb 2023 16:19:30 +0100
From: Frederic Weisbecker <frederic@...nel.org>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Yu Liao <liaoyu15@...wei.com>, fweisbec@...il.com,
mingo@...nel.org, liwei391@...wei.com, adobriyan@...il.com,
mirsad.todorovac@....unizg.hr, linux-kernel@...r.kernel.org,
Peter Zijlstra <peterz@...radead.org>
Subject: [PATCH] timers/nohz: Restructure and reshuffle struct tick_sched
On Tue, Jan 31, 2023 at 03:44:00PM +0100, Thomas Gleixner wrote:
> @Frederic: This structure is patently unstructured and if we fix this
> issue here then we really want to look at the cache line layout for
> real.
I'm not really good at that, but here is my try:
---
From: Frederic Weisbecker <frederic@...nel.org>
Date: Wed, 8 Feb 2023 16:08:11 +0100
Subject: [PATCH] timers/nohz: Restructure and reshuffle struct tick_sched
Restructure and group fields by access in order to optimize cache
layout. While at it, also add missing kernel doc for two fields:
@last_jiffies and @idle_expires.
Reported-by: Thomas Gleixner <tglx@...utronix.de>
Signed-off-by: Frederic Weisbecker <frederic@...nel.org>
---
kernel/time/tick-sched.h | 66 +++++++++++++++++++++++++---------------
1 file changed, 41 insertions(+), 25 deletions(-)
diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h
index 504649513399..c6663254d17d 100644
--- a/kernel/time/tick-sched.h
+++ b/kernel/time/tick-sched.h
@@ -22,65 +22,81 @@ enum tick_nohz_mode {
/**
* struct tick_sched - sched tick emulation and no idle tick control/stats
- * @sched_timer: hrtimer to schedule the periodic tick in high
- * resolution mode
- * @check_clocks: Notification mechanism about clocksource changes
- * @nohz_mode: Mode - one state of tick_nohz_mode
+ *
* @inidle: Indicator that the CPU is in the tick idle mode
* @tick_stopped: Indicator that the idle tick has been stopped
* @idle_active: Indicator that the CPU is actively in the tick idle mode;
* it is reset during irq handling phases.
- * @do_timer_lst: CPU was the last one doing do_timer before going idle
+ * @do_timer_last: CPU was the last one doing do_timer before going idle
* @got_idle_tick: Tick timer function has run with @inidle set
+ * @stalled_jiffies: Number of stalled jiffies detected across ticks
+ * @last_tick_jiffies: Value of jiffies seen on last tick
+ * @sched_timer: hrtimer to schedule the periodic tick in high
+ * resolution mode
* @last_tick: Store the last tick expiry time when the tick
* timer is modified for nohz sleeps. This is necessary
* to resume the tick timer operation in the timeline
* when the CPU returns from nohz sleep.
* @next_tick: Next tick to be fired when in dynticks mode.
* @idle_jiffies: jiffies at the entry to idle for idle time accounting
+ * @idle_waketime: Time when the idle was interrupted
+ * @idle_entrytime: Time when the idle call was entered
+ * @nohz_mode: Mode - one state of tick_nohz_mode
+ * @last_jiffies: Base jiffies snapshot when next event was last computed
+ * @timer_expires_base: Base time clock monotonic for @timer_expires
+ * @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
+ * @next_timer: Expiry time of next expiring timer for debugging purpose only
+ * @idle_expires: Next tick in idle, for debugging purpose only
* @idle_calls: Total number of idle calls
* @idle_sleeps: Number of idle calls, where the sched tick was stopped
- * @idle_entrytime: Time when the idle call was entered
- * @idle_waketime: Time when the idle was interrupted
* @idle_exittime: Time when the idle state was left
* @idle_sleeptime: Sum of the time slept in idle with sched tick stopped
* @iowait_sleeptime: Sum of the time slept in idle with sched tick stopped, with IO outstanding
- * @timer_expires: Anticipated timer expiration time (in case sched tick is stopped)
- * @timer_expires_base: Base time clock monotonic for @timer_expires
- * @next_timer: Expiry time of next expiring timer for debugging purpose only
* @tick_dep_mask: Tick dependency mask - is set, if someone needs the tick
- * @last_tick_jiffies: Value of jiffies seen on last tick
- * @stalled_jiffies: Number of stalled jiffies detected across ticks
+ * @check_clocks: Notification mechanism about clocksource changes
*/
struct tick_sched {
- struct hrtimer sched_timer;
- unsigned long check_clocks;
- enum tick_nohz_mode nohz_mode;
-
+ /* Common flags */
unsigned int inidle : 1;
unsigned int tick_stopped : 1;
unsigned int idle_active : 1;
unsigned int do_timer_last : 1;
unsigned int got_idle_tick : 1;
+ /* Tick handling: jiffies stall check */
+ unsigned int stalled_jiffies;
+ unsigned long last_tick_jiffies;
+
+ /* Tick handling */
+ struct hrtimer sched_timer;
ktime_t last_tick;
ktime_t next_tick;
unsigned long idle_jiffies;
- unsigned long idle_calls;
- unsigned long idle_sleeps;
- ktime_t idle_entrytime;
ktime_t idle_waketime;
- ktime_t idle_exittime;
- ktime_t idle_sleeptime;
- ktime_t iowait_sleeptime;
+
+ /* Idle entry */
+ ktime_t idle_entrytime;
+
+ /* Tick stop */
+ enum tick_nohz_mode nohz_mode;
unsigned long last_jiffies;
- u64 timer_expires;
u64 timer_expires_base;
+ u64 timer_expires;
u64 next_timer;
ktime_t idle_expires;
+ unsigned long idle_calls;
+ unsigned long idle_sleeps;
+
+ /* Idle exit */
+ ktime_t idle_exittime;
+ ktime_t idle_sleeptime;
+ ktime_t iowait_sleeptime;
+
+ /* Full dynticks handling */
atomic_t tick_dep_mask;
- unsigned long last_tick_jiffies;
- unsigned int stalled_jiffies;
+
+ /* Clocksource changes */
+ unsigned long check_clocks;
};
extern struct tick_sched *tick_get_tick_sched(int cpu);
--
2.34.1
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