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-rw-r--r--kernel/sched/core.c7
-rw-r--r--kernel/time/Kconfig11
-rw-r--r--kernel/time/posix-cpu-timers.c4
-rw-r--r--kernel/time/tick-sched.c129
4 files changed, 102 insertions, 49 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4a2a448d8dd4..cf16f8fda9a6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1928,6 +1928,11 @@ static inline void uclamp_post_fork(struct task_struct *p) { }
static inline void init_uclamp(void) { }
#endif /* CONFIG_UCLAMP_TASK */
+bool sched_task_on_rq(struct task_struct *p)
+{
+ return task_on_rq_queued(p);
+}
+
static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags)
{
if (!(flags & ENQUEUE_NOCLOCK))
@@ -4546,6 +4551,7 @@ static struct rq *finish_task_switch(struct task_struct *prev)
vtime_task_switch(prev);
perf_event_task_sched_in(prev, current);
finish_task(prev);
+ tick_nohz_task_switch();
finish_lock_switch(rq);
finish_arch_post_lock_switch();
kcov_finish_switch(current);
@@ -4591,7 +4597,6 @@ static struct rq *finish_task_switch(struct task_struct *prev)
put_task_struct_rcu_user(prev);
}
- tick_nohz_task_switch();
return rq;
}
diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig
index 83e158d016ba..7df71ef0e1fd 100644
--- a/kernel/time/Kconfig
+++ b/kernel/time/Kconfig
@@ -117,13 +117,14 @@ config NO_HZ_FULL
the task mostly runs in userspace and has few kernel activity.
You need to fill up the nohz_full boot parameter with the
- desired range of dynticks CPUs.
+ desired range of dynticks CPUs to use it. This is implemented at
+ the expense of some overhead in user <-> kernel transitions:
+ syscalls, exceptions and interrupts.
- This is implemented at the expense of some overhead in user <-> kernel
- transitions: syscalls, exceptions and interrupts. Even when it's
- dynamically off.
+ By default, without passing the nohz_full parameter, this behaves just
+ like NO_HZ_IDLE.
- Say N.
+ If you're a distro say Y.
endchoice
diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c
index 3bb96a8b49c9..29a5e54e6e10 100644
--- a/kernel/time/posix-cpu-timers.c
+++ b/kernel/time/posix-cpu-timers.c
@@ -523,7 +523,7 @@ static void arm_timer(struct k_itimer *timer, struct task_struct *p)
if (CPUCLOCK_PERTHREAD(timer->it_clock))
tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
else
- tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER);
+ tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
}
/*
@@ -1358,7 +1358,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
if (*newval < *nextevt)
*nextevt = *newval;
- tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER);
+ tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
}
static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 6784f27a3099..6bffe5af8cb1 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -323,6 +323,46 @@ void tick_nohz_full_kick_cpu(int cpu)
irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
}
+static void tick_nohz_kick_task(struct task_struct *tsk)
+{
+ int cpu;
+
+ /*
+ * If the task is not running, run_posix_cpu_timers()
+ * has nothing to elapse, IPI can then be spared.
+ *
+ * activate_task() STORE p->tick_dep_mask
+ * STORE p->on_rq
+ * __schedule() (switch to task 'p') smp_mb() (atomic_fetch_or())
+ * LOCK rq->lock LOAD p->on_rq
+ * smp_mb__after_spin_lock()
+ * tick_nohz_task_switch()
+ * LOAD p->tick_dep_mask
+ */
+ if (!sched_task_on_rq(tsk))
+ return;
+
+ /*
+ * If the task concurrently migrates to another CPU,
+ * we guarantee it sees the new tick dependency upon
+ * schedule.
+ *
+ * set_task_cpu(p, cpu);
+ * STORE p->cpu = @cpu
+ * __schedule() (switch to task 'p')
+ * LOCK rq->lock
+ * smp_mb__after_spin_lock() STORE p->tick_dep_mask
+ * tick_nohz_task_switch() smp_mb() (atomic_fetch_or())
+ * LOAD p->tick_dep_mask LOAD p->cpu
+ */
+ cpu = task_cpu(tsk);
+
+ preempt_disable();
+ if (cpu_online(cpu))
+ tick_nohz_full_kick_cpu(cpu);
+ preempt_enable();
+}
+
/*
* Kick all full dynticks CPUs in order to force these to re-evaluate
* their dependency on the tick and restart it if necessary.
@@ -405,19 +445,8 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
*/
void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
{
- if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask)) {
- if (tsk == current) {
- preempt_disable();
- tick_nohz_full_kick();
- preempt_enable();
- } else {
- /*
- * Some future tick_nohz_full_kick_task()
- * should optimize this.
- */
- tick_nohz_full_kick_all();
- }
- }
+ if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
+ tick_nohz_kick_task(tsk);
}
EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
@@ -431,9 +460,20 @@ EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
* Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
* per process timers.
*/
-void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit)
+void tick_nohz_dep_set_signal(struct task_struct *tsk,
+ enum tick_dep_bits bit)
{
- tick_nohz_dep_set_all(&sig->tick_dep_mask, bit);
+ int prev;
+ struct signal_struct *sig = tsk->signal;
+
+ prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);
+ if (!prev) {
+ struct task_struct *t;
+
+ lockdep_assert_held(&tsk->sighand->siglock);
+ __for_each_thread(sig, t)
+ tick_nohz_kick_task(t);
+ }
}
void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
@@ -448,13 +488,10 @@ void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bi
*/
void __tick_nohz_task_switch(void)
{
- unsigned long flags;
struct tick_sched *ts;
- local_irq_save(flags);
-
if (!tick_nohz_full_cpu(smp_processor_id()))
- goto out;
+ return;
ts = this_cpu_ptr(&tick_cpu_sched);
@@ -463,8 +500,6 @@ void __tick_nohz_task_switch(void)
atomic_read(&current->signal->tick_dep_mask))
tick_nohz_full_kick();
}
-out:
- local_irq_restore(flags);
}
/* Get the boot-time nohz CPU list from the kernel parameters. */
@@ -922,27 +957,31 @@ static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
* Cancel the scheduled timer and restore the tick
*/
ts->tick_stopped = 0;
- ts->idle_exittime = now;
-
tick_nohz_restart(ts, now);
}
-static void tick_nohz_full_update_tick(struct tick_sched *ts)
+static void __tick_nohz_full_update_tick(struct tick_sched *ts,
+ ktime_t now)
{
#ifdef CONFIG_NO_HZ_FULL
int cpu = smp_processor_id();
- if (!tick_nohz_full_cpu(cpu))
+ if (can_stop_full_tick(cpu, ts))
+ tick_nohz_stop_sched_tick(ts, cpu);
+ else if (ts->tick_stopped)
+ tick_nohz_restart_sched_tick(ts, now);
+#endif
+}
+
+static void tick_nohz_full_update_tick(struct tick_sched *ts)
+{
+ if (!tick_nohz_full_cpu(smp_processor_id()))
return;
if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
return;
- if (can_stop_full_tick(cpu, ts))
- tick_nohz_stop_sched_tick(ts, cpu);
- else if (ts->tick_stopped)
- tick_nohz_restart_sched_tick(ts, ktime_get());
-#endif
+ __tick_nohz_full_update_tick(ts, ktime_get());
}
static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
@@ -1189,11 +1228,13 @@ unsigned long tick_nohz_get_idle_calls(void)
return ts->idle_calls;
}
-static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
+static void tick_nohz_account_idle_time(struct tick_sched *ts,
+ ktime_t now)
{
-#ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
unsigned long ticks;
+ ts->idle_exittime = now;
+
if (vtime_accounting_enabled_this_cpu())
return;
/*
@@ -1207,21 +1248,27 @@ static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
*/
if (ticks && ticks < LONG_MAX)
account_idle_ticks(ticks);
-#endif
}
-static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now)
+void tick_nohz_idle_restart_tick(void)
{
- tick_nohz_restart_sched_tick(ts, now);
- tick_nohz_account_idle_ticks(ts);
+ struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+
+ if (ts->tick_stopped) {
+ ktime_t now = ktime_get();
+ tick_nohz_restart_sched_tick(ts, now);
+ tick_nohz_account_idle_time(ts, now);
+ }
}
-void tick_nohz_idle_restart_tick(void)
+static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
{
- struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
+ if (tick_nohz_full_cpu(smp_processor_id()))
+ __tick_nohz_full_update_tick(ts, now);
+ else
+ tick_nohz_restart_sched_tick(ts, now);
- if (ts->tick_stopped)
- __tick_nohz_idle_restart_tick(ts, ktime_get());
+ tick_nohz_account_idle_time(ts, now);
}
/**
@@ -1253,7 +1300,7 @@ void tick_nohz_idle_exit(void)
tick_nohz_stop_idle(ts, now);
if (tick_stopped)
- __tick_nohz_idle_restart_tick(ts, now);
+ tick_nohz_idle_update_tick(ts, now);
local_irq_enable();
}
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-22 23:25:19 +0000