[PATCH 3/5] sched/vtime: Consolidate IRQ time accounting

From: Frederic Weisbecker
Date: Wed Dec 02 2020 - 06:58:47 EST

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The 3 architectures implementing CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
all have their own version of irq time accounting that dispatch the
cputime to the appropriate index: hardirq, softirq, system, idle,
guest... from an all-in-one function.

Instead of having these ad-hoc versions, move the cputime destination
dispatch decision to the core code and leave only the actual per-index
cputime accounting to the architecture.

Signed-off-by: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Tony Luck <tony.luck@xxxxxxxxx>
Cc: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
---
arch/ia64/kernel/time.c | 20 +++++++++----
arch/powerpc/kernel/time.c | 58 +++++++++++++++++++++++++++-----------
arch/s390/kernel/vtime.c | 51 ++++++++++++++++++++++-----------
include/linux/vtime.h | 16 ++++-------
kernel/sched/cputime.c | 13 ++++++---
5 files changed, 106 insertions(+), 52 deletions(-)

diff --git a/arch/ia64/kernel/time.c b/arch/ia64/kernel/time.c
index 7abc5f37bfaf..733e0e3324b8 100644
--- a/arch/ia64/kernel/time.c
+++ b/arch/ia64/kernel/time.c
@@ -138,12 +138,8 @@ void vtime_account_kernel(struct task_struct *tsk)
struct thread_info *ti = task_thread_info(tsk);
__u64 stime = vtime_delta(tsk);

- if ((tsk->flags & PF_VCPU) && !irq_count())
+ if (tsk->flags & PF_VCPU)
ti->gtime += stime;
- else if (hardirq_count())
- ti->hardirq_time += stime;
- else if (in_serving_softirq())
- ti->softirq_time += stime;
else
ti->stime += stime;
}
@@ -156,6 +152,20 @@ void vtime_account_idle(struct task_struct *tsk)
ti->idle_time += vtime_delta(tsk);
}

+void vtime_account_softirq(struct task_struct *tsk)
+{
+ struct thread_info *ti = task_thread_info(tsk);
+
+ ti->softirq_time += vtime_delta(tsk);
+}
+
+void vtime_account_hardirq(struct task_struct *tsk)
+{
+ struct thread_info *ti = task_thread_info(tsk);
+
+ ti->hardirq_time += vtime_delta(tsk);
+}
+
#endif /* CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */

static irqreturn_t
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c
index 74efe46f5532..cf3f8db7e0e3 100644
--- a/arch/powerpc/kernel/time.c
+++ b/arch/powerpc/kernel/time.c
@@ -311,12 +311,11 @@ static unsigned long vtime_delta_scaled(struct cpu_accounting_data *acct,
return stime_scaled;
}

-static unsigned long vtime_delta(struct task_struct *tsk,
+static unsigned long vtime_delta(struct cpu_accounting_data *acct,
unsigned long *stime_scaled,
unsigned long *steal_time)
{
unsigned long now, stime;
- struct cpu_accounting_data *acct = get_accounting(tsk);

WARN_ON_ONCE(!irqs_disabled());

@@ -331,29 +330,30 @@ static unsigned long vtime_delta(struct task_struct *tsk,
return stime;
}

-void vtime_account_kernel(struct task_struct *tsk)
+static void vtime_delta_kernel(struct cpu_accounting_data *acct,
+ unsigned long *stime, unsigned long *stime_scaled)
{
- unsigned long stime, stime_scaled, steal_time;
- struct cpu_accounting_data *acct = get_accounting(tsk);
+ unsigned long steal_time;

- stime = vtime_delta(tsk, &stime_scaled, &steal_time);
-
- stime -= min(stime, steal_time);
+ *stime = vtime_delta(acct, stime_scaled, &steal_time);
+ *stime -= min(*stime, steal_time);
acct->steal_time += steal_time;
+}

- if ((tsk->flags & PF_VCPU) && !irq_count()) {
+void vtime_account_kernel(struct task_struct *tsk)
+{
+ struct cpu_accounting_data *acct = get_accounting(tsk);
+ unsigned long stime, stime_scaled;
+
+ vtime_delta_kernel(acct, &stime, &stime_scaled);
+
+ if (tsk->flags & PF_VCPU) {
acct->gtime += stime;
#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->utime_scaled += stime_scaled;
#endif
} else {
- if (hardirq_count())
- acct->hardirq_time += stime;
- else if (in_serving_softirq())
- acct->softirq_time += stime;
- else
- acct->stime += stime;
-
+ acct->stime += stime;
#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
acct->stime_scaled += stime_scaled;
#endif
@@ -366,10 +366,34 @@ void vtime_account_idle(struct task_struct *tsk)
unsigned long stime, stime_scaled, steal_time;
struct cpu_accounting_data *acct = get_accounting(tsk);

- stime = vtime_delta(tsk, &stime_scaled, &steal_time);
+ stime = vtime_delta(acct, &stime_scaled, &steal_time);
acct->idle_time += stime + steal_time;
}

+static void vtime_account_irq_field(struct cpu_accounting_data *acct,
+ unsigned long *field)
+{
+ unsigned long stime, stime_scaled;
+
+ vtime_delta_kernel(acct, &stime, &stime_scaled);
+ *field += stime;
+#ifdef CONFIG_ARCH_HAS_SCALED_CPUTIME
+ acct->stime_scaled += stime_scaled;
+#endif
+}
+
+void vtime_account_softirq(struct task_struct *tsk)
+{
+ struct cpu_accounting_data *acct = get_accounting(tsk);
+ vtime_account_irq_field(acct, &acct->softirq_time);
+}
+
+void vtime_account_hardirq(struct task_struct *tsk)
+{
+ struct cpu_accounting_data *acct = get_accounting(tsk);
+ vtime_account_irq_field(acct, &acct->hardirq_time);
+}
+
static void vtime_flush_scaled(struct task_struct *tsk,
struct cpu_accounting_data *acct)
{
diff --git a/arch/s390/kernel/vtime.c b/arch/s390/kernel/vtime.c
index ebd8e5655789..5aaa2ca6a928 100644
--- a/arch/s390/kernel/vtime.c
+++ b/arch/s390/kernel/vtime.c
@@ -222,31 +222,50 @@ void vtime_flush(struct task_struct *tsk)
S390_lowcore.avg_steal_timer = avg_steal;
}

-/*
- * Update process times based on virtual cpu times stored by entry.S
- * to the lowcore fields user_timer, system_timer & steal_clock.
- */
-void vtime_account_kernel(struct task_struct *tsk)
+static u64 vtime_delta(void)
{
- u64 timer;
+ u64 timer = S390_lowcore.last_update_timer;

- timer = S390_lowcore.last_update_timer;
S390_lowcore.last_update_timer = get_vtimer();
- timer -= S390_lowcore.last_update_timer;

- if ((tsk->flags & PF_VCPU) && (irq_count() == 0))
- S390_lowcore.guest_timer += timer;
- else if (hardirq_count())
- S390_lowcore.hardirq_timer += timer;
- else if (in_serving_softirq())
- S390_lowcore.softirq_timer += timer;
+ return timer - S390_lowcore.last_update_timer;
+}
+
+/*
+ * Update process times based on virtual cpu times stored by entry.S
+ * to the lowcore fields user_timer, system_timer & steal_clock.
+ */
+void vtime_account_kernel(struct task_struct *tsk)
+{
+ u64 delta = vtime_delta();
+
+ if (tsk->flags & PF_VCPU)
+ S390_lowcore.guest_timer += delta;
else
- S390_lowcore.system_timer += timer;
+ S390_lowcore.system_timer += delta;

- virt_timer_forward(timer);
+ virt_timer_forward(delta);
}
EXPORT_SYMBOL_GPL(vtime_account_kernel);

+void vtime_account_softirq(struct task_struct *tsk)
+{
+ u64 delta = vtime_delta();
+
+ S390_lowcore.softirq_timer += delta;
+
+ virt_timer_forward(delta);
+}
+
+void vtime_account_hardirq(struct task_struct *tsk)
+{
+ u64 delta = vtime_delta();
+
+ S390_lowcore.hardirq_timer += delta;
+
+ virt_timer_forward(delta);
+}
+
/*
* Sorted add to a list. List is linear searched until first bigger
* element is found.
diff --git a/include/linux/vtime.h b/include/linux/vtime.h
index 2cdeca062db3..6c9867419615 100644
--- a/include/linux/vtime.h
+++ b/include/linux/vtime.h
@@ -83,16 +83,12 @@ static inline void vtime_init_idle(struct task_struct *tsk, int cpu) { }
#endif

#ifdef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
-extern void vtime_account_irq_enter(struct task_struct *tsk);
-static inline void vtime_account_irq_exit(struct task_struct *tsk)
-{
- /* On hard|softirq exit we always account to hard|softirq cputime */
- vtime_account_kernel(tsk);
-}
+extern void vtime_account_irq(struct task_struct *tsk);
+extern void vtime_account_softirq(struct task_struct *tsk);
+extern void vtime_account_hardirq(struct task_struct *tsk);
extern void vtime_flush(struct task_struct *tsk);
#else /* !CONFIG_VIRT_CPU_ACCOUNTING_NATIVE */
-static inline void vtime_account_irq_enter(struct task_struct *tsk) { }
-static inline void vtime_account_irq_exit(struct task_struct *tsk) { }
+static inline void vtime_account_irq(struct task_struct *tsk) { }
static inline void vtime_flush(struct task_struct *tsk) { }
#endif

@@ -105,13 +101,13 @@ static inline void irqtime_account_irq(struct task_struct *tsk) { }

static inline void account_irq_enter_time(struct task_struct *tsk)
{
- vtime_account_irq_enter(tsk);
+ vtime_account_irq(tsk);
irqtime_account_irq(tsk);
}

static inline void account_irq_exit_time(struct task_struct *tsk)
{
- vtime_account_irq_exit(tsk);
+ vtime_account_irq(tsk);
irqtime_account_irq(tsk);
}

diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
index 2783162542b1..02163d4260d7 100644
--- a/kernel/sched/cputime.c
+++ b/kernel/sched/cputime.c
@@ -417,13 +417,18 @@ void vtime_task_switch(struct task_struct *prev)
}
# endif

-void vtime_account_irq_enter(struct task_struct *tsk)
+void vtime_account_irq(struct task_struct *tsk)
{
- if (!IS_ENABLED(CONFIG_HAVE_VIRT_CPU_ACCOUNTING_IDLE) &&
- !in_interrupt() && is_idle_task(tsk))
+ if (hardirq_count()) {
+ vtime_account_hardirq(tsk);
+ } else if (in_serving_softirq()) {
+ vtime_account_softirq(tsk);
+ } else if (!IS_ENABLED(CONFIG_HAVE_VIRT_CPU_ACCOUNTING_IDLE) &&
+ is_idle_task(tsk)) {
vtime_account_idle(tsk);
- else
+ } else {
vtime_account_kernel(tsk);
+ }
}

void cputime_adjust(struct task_cputime *curr, struct prev_cputime *prev,
--
2.25.1

Next message: Frederic Weisbecker: "[PATCH 4/5] irqtime: Move irqtime entry accounting after irq offset incrementation"
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