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Date: Sun, 28 Jan 2007 18:11:49 +0100
From: Karsten Wiese <fzu@...gehoertderstaat.de>
To: Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH -rt] high_res_timers: precisely update_process_times; Take2
With NO_HZ or HIGH_RES_TIMERS update_process_times() can be called,
when jiffies increments != 1 have to be acounted for.
Cope with these situations by splitting update_process_times() into
__update_process_times() and tick().
New in Take 2 is an attempt to make patch work for SMP also.
This is done by adding
unsigned long update_process_times_jiffies;
to per cpu struct tick_sched.
update_process_times_jiffies is set whenever an unseen yet jiffies value
is seen by a particular cpu after calls to tick_do_update_jiffies64().
Fixes cpufreq_ondemand going nuts here on an AMD64 UP running 2.6.20-rc6-rt2.
Does it work on SMP? (don't have any)
Signed-off-by: Karsten Wiese <fzu@...gehoertderstaat.de>
diff -pur rc6-rt2/include/linux/sched.h rc6-rt2-kw/include/linux/sched.h
--- rc6-rt2/include/linux/sched.h 2007-01-26 14:42:55.000000000 +0100
+++ rc6-rt2-kw/include/linux/sched.h 2007-01-28 02:02:29.000000000 +0100
@@ -264,6 +264,13 @@ long io_schedule_timeout(long timeout);
extern void cpu_init (void);
extern void trap_init(void);
extern void update_process_times(int user);
+#ifdef CONFIG_HIGH_RES_TIMERS
+extern void __update_process_times(int user_tick, unsigned long ticks);
+extern void tick(int user_tick);
+#define NO_HIGH_RES_TIMERS_STATIC
+#else
+#define NO_HIGH_RES_TIMERS_STATIC static
+#endif
extern void scheduler_tick(void);
#ifdef CONFIG_GENERIC_HARDIRQS
Nur in rc6-rt2-kw/include/linux: sched.h~.
diff -pur rc6-rt2/include/linux/tick.h rc6-rt2-kw/include/linux/tick.h
--- rc6-rt2/include/linux/tick.h 2007-01-26 14:42:55.000000000 +0100
+++ rc6-rt2-kw/include/linux/tick.h 2007-01-28 16:19:40.000000000 +0100
@@ -56,6 +56,7 @@ struct tick_sched {
unsigned long last_jiffies;
unsigned long next_jiffies;
ktime_t idle_expires;
+ unsigned long update_process_times_jiffies;
};
extern void __init tick_init(void);
diff -pur rc6-rt2/kernel/time/tick-common.c rc6-rt2-kw/kernel/time/tick-common.c
--- rc6-rt2/kernel/time/tick-common.c 2007-01-26 14:42:55.000000000 +0100
+++ rc6-rt2-kw/kernel/time/tick-common.c 2007-01-28 16:20:00.000000000 +0100
@@ -57,6 +57,8 @@ int tick_is_oneshot_available(void)
*/
static void tick_periodic(int cpu)
{
+ struct tick_sched *ts = tick_get_tick_sched(smp_processor_id());
+
if (tick_do_timer_cpu == cpu) {
write_seqlock(&xtime_lock);
@@ -67,6 +69,8 @@ static void tick_periodic(int cpu)
write_sequnlock(&xtime_lock);
}
+ ts->update_process_times_jiffies = jiffies;
+
update_process_times(user_mode(get_irq_regs()));
// profile_tick(CPU_PROFILING);
}
Nur in rc6-rt2-kw/kernel/time: tick-common.c~.
diff -pur rc6-rt2/kernel/time/tick-sched.c rc6-rt2-kw/kernel/time/tick-sched.c
--- rc6-rt2/kernel/time/tick-sched.c 2007-01-26 14:42:55.000000000 +0100
+++ rc6-rt2-kw/kernel/time/tick-sched.c 2007-01-28 17:21:34.000000000 +0100
@@ -148,6 +148,7 @@ void tick_nohz_update_jiffies(void)
local_irq_save(flags);
tick_do_update_jiffies64(now);
+ ts->update_process_times_jiffies = jiffies;
local_irq_restore(flags);
}
@@ -237,6 +238,7 @@ void tick_nohz_stop_sched_tick(void)
* softirq.
*/
tick_do_update_jiffies64(ktime_get());
+ ts->update_process_times_jiffies = jiffies;
}
raise_softirq_irqoff(TIMER_SOFTIRQ);
out:
@@ -265,6 +267,7 @@ void tick_nohz_restart_sched_tick(void)
local_irq_disable();
tick_do_update_jiffies64(now);
+ ts->update_process_times_jiffies = jiffies;
/* Account the idle time */
delta = ktime_sub(now, ts->idle_entrytime);
@@ -310,6 +313,7 @@ void tick_nohz_restart_sched_tick(void)
}
/* Update jiffies and reread time */
tick_do_update_jiffies64(now);
+ ts->update_process_times_jiffies = jiffies;
now = ktime_get();
}
local_irq_enable();
@@ -329,27 +333,36 @@ static void tick_nohz_handler(struct clo
struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched);
struct pt_regs *regs = get_irq_regs();
ktime_t now = ktime_get();
-
+ unsigned long ticks;
+ unsigned long jiffies_now;
dev->next_event.tv64 = KTIME_MAX;
/* Check, if the jiffies need an update */
tick_do_update_jiffies64(now);
- /*
- * When we are idle and the tick is stopped, we have to touch
- * the watchdog as we might not schedule for a really long
- * time. This happens on complete idle SMP systems while
- * waiting on the login prompt. We also increment the "start
- * of idle" jiffy stamp so the idle accounting adjustment we
- * do when we go busy again does not account too much ticks.
- */
- if (ts->tick_stopped) {
- touch_softlockup_watchdog();
- ts->idle_jiffies++;
+ /* Has this jiffie been seen on this cpu ? */
+ jiffies_now = jiffies;
+ ticks = jiffies_now - ts->update_process_times_jiffies;
+ ts->update_process_times_jiffies = jiffies_now;
+
+ if (ticks) {
+ /*
+ * When we are idle and the tick is stopped, we have to touch
+ * the watchdog as we might not schedule for a really long
+ * time. This happens on complete idle SMP systems while
+ * waiting on the login prompt. We also increment the "start of
+ * idle" jiffy stamp so the idle accounting adjustment we do
+ * when we go busy again does not account too much ticks.
+ */
+ if (ts->tick_stopped) {
+ touch_softlockup_watchdog();
+ ts->idle_jiffies++;
+ __update_process_times(user_mode(regs), 1);
+ } else
+ __update_process_times(user_mode(regs), ticks);
}
- update_process_times(user_mode(regs));
-// profile_tick(CPU_PROFILING);
+ tick(user_mode(regs));
/* Do not restart, when we are in the idle loop */
if (ts->tick_stopped)
@@ -358,6 +371,7 @@ static void tick_nohz_handler(struct clo
while (tick_nohz_reprogram(ts, now)) {
now = ktime_get();
tick_do_update_jiffies64(now);
+ ts->update_process_times_jiffies = jiffies;
}
}
@@ -421,34 +435,45 @@ static enum hrtimer_restart tick_sched_t
struct hrtimer_cpu_base *base = timer->base->cpu_base;
struct pt_regs *regs = get_irq_regs();
ktime_t now = ktime_get();
+ unsigned long ticks;
+ unsigned long jiffies_now;
/* Check, if the jiffies need an update */
tick_do_update_jiffies64(now);
+ /* Has this jiffie been seen on this cpu ? */
+ jiffies_now = jiffies;
+ ticks = jiffies_now - ts->update_process_times_jiffies;
+ ts->update_process_times_jiffies = jiffies_now;
+
/*
* Do not call, when we are not in irq context and have
* no valid regs pointer
*/
if (regs) {
- /*
- * When we are idle and the tick is stopped, we have to touch
- * the watchdog as we might not schedule for a really long
- * time. This happens on complete idle SMP systems while
- * waiting on the login prompt. We also increment the "start of
- * idle" jiffy stamp so the idle accounting adjustment we do
- * when we go busy again does not account too much ticks.
- */
- if (ts->tick_stopped) {
- touch_softlockup_watchdog();
- ts->idle_jiffies++;
+ if (ticks) {
+ /*
+ * When we are idle and the tick is stopped, we have to touch
+ * the watchdog as we might not schedule for a really long
+ * time. This happens on complete idle SMP systems while
+ * waiting on the login prompt. We also increment the "start of
+ * idle" jiffy stamp so the idle accounting adjustment we do
+ * when we go busy again does not account too much ticks.
+ */
+ if (ts->tick_stopped) {
+ touch_softlockup_watchdog();
+ ts->idle_jiffies++;
+ __update_process_times(user_mode(regs), 1);
+ } else
+ __update_process_times(user_mode(regs), ticks);
}
/*
- * update_process_times() might take tasklist_lock, hence
+ * tick() might take tasklist_lock, hence
* drop the base lock. sched-tick hrtimers are per-CPU and
* never accessible by userspace APIs, so this is safe to do.
*/
spin_unlock(&base->lock);
- update_process_times(user_mode(regs));
+ tick(user_mode(regs));
// profile_tick(CPU_PROFILING);
spin_lock(&base->lock);
}
Nur in rc6-rt2-kw/kernel/time: tick-sched.c~.
diff -pur rc6-rt2/kernel/timer.c rc6-rt2-kw/kernel/timer.c
--- rc6-rt2/kernel/timer.c 2007-01-26 14:42:55.000000000 +0100
+++ rc6-rt2-kw/kernel/timer.c 2007-01-28 02:03:01.000000000 +0100
@@ -1312,20 +1312,24 @@ static void update_wall_time(void)
update_vsyscall(&xtime, clock);
}
-/*
- * Called from the timer interrupt handler to charge one tick to the current
- * process. user_tick is 1 if the tick is user time, 0 for system.
- */
-void update_process_times(int user_tick)
+NO_HIGH_RES_TIMERS_STATIC
+void __update_process_times(int user_tick, unsigned long ticks)
{
- int cpu = smp_processor_id();
struct task_struct *p = current;
/* Note: this timer irq context must be accounted for as well. */
if (user_tick)
- account_user_time(p, jiffies_to_cputime(1));
+ account_user_time(p, jiffies_to_cputime(ticks));
else
- account_system_time(p, HARDIRQ_OFFSET, jiffies_to_cputime(1));
+ account_system_time(p, HARDIRQ_OFFSET, jiffies_to_cputime(ticks));
+}
+
+NO_HIGH_RES_TIMERS_STATIC
+void tick(int user_tick)
+{
+ int cpu = smp_processor_id();
+ struct task_struct *p = current;
+
scheduler_tick();
run_local_timers();
if (rcu_pending(cpu))
@@ -1334,6 +1338,16 @@ void update_process_times(int user_tick)
}
/*
+ * Called from the timer interrupt handler to charge one tick to the current
+ * process. user_tick is 1 if the tick is user time, 0 for system.
+ */
+void update_process_times(int user_tick)
+{
+ __update_process_times(user_tick, 1);
+ tick(user_tick);
+}
+
+/*
* Nr of active tasks - counted in fixed-point numbers
*/
static unsigned long count_active_tasks(void)
-
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