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Message-ID: <CAKc596KLgwE98Hch-WMCFM38W=FryronqASgn2ih3U_-+YU3ww@mail.gmail.com>
Date: Tue, 13 Oct 2020 11:10:24 +0800
From: jun qian <qianjun.kernel@...il.com>
To: Pingfan Liu <kernelfans@...il.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
Juri Lelli <juri.lelli@...hat.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Dietmar Eggemann <dietmar.eggemann@....com>,
Steven Rostedt <rostedt@...dmis.org>,
Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
Thomas Gleixner <tglx@...utronix.de>,
Andy Lutomirski <luto@...nel.org>,
Will Deacon <will@...nel.org>,
"Paul E. McKenney" <paulmck@...nel.org>,
Frederic Weisbecker <frederic@...nel.org>,
Allen Pais <allen.lkml@...il.com>,
Romain Perier <romain.perier@...il.com>
Subject: Re: [PATCH] sched/cputime: correct account of irqtime
Pingfan Liu <kernelfans@...il.com> 于2020年10月12日周一 下午9:54写道：
>
> __do_softirq() may be interrupted by hardware interrupts. In this case,
> irqtime_account_irq() will account the time slice as CPUTIME_SOFTIRQ by
> mistake.
>
> By passing irqtime_account_irq() an extra param about either hardirq or
> softirq, irqtime_account_irq() can handle the above case.
>
> Signed-off-by: Pingfan Liu <kernelfans@...il.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Juri Lelli <juri.lelli@...hat.com>
> Cc: Vincent Guittot <vincent.guittot@...aro.org>
> Cc: Dietmar Eggemann <dietmar.eggemann@....com>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Ben Segall <bsegall@...gle.com>
> Cc: Mel Gorman <mgorman@...e.de>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: Will Deacon <will@...nel.org>
> Cc: "Paul E. McKenney" <paulmck@...nel.org>
> Cc: Frederic Weisbecker <frederic@...nel.org>
> Cc: Allen Pais <allen.lkml@...il.com>
> Cc: Romain Perier <romain.perier@...il.com>
> To: linux-kernel@...r.kernel.org
> ---
> include/linux/hardirq.h | 4 ++--
> include/linux/vtime.h | 12 ++++++------
> kernel/sched/cputime.c | 4 ++--
> kernel/softirq.c | 6 +++---
> 4 files changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h
> index 754f67a..56e7bb5 100644
> --- a/include/linux/hardirq.h
> +++ b/include/linux/hardirq.h
> @@ -32,7 +32,7 @@ static __always_inline void rcu_irq_enter_check_tick(void)
> */
> #define __irq_enter() \
> do { \
> - account_irq_enter_time(current); \
> + account_irq_enter_time(current, true); \
> preempt_count_add(HARDIRQ_OFFSET); \
> lockdep_hardirq_enter(); \
> } while (0)
> @@ -63,7 +63,7 @@ void irq_enter_rcu(void);
> #define __irq_exit() \
> do { \
> lockdep_hardirq_exit(); \
> - account_irq_exit_time(current); \
> + account_irq_exit_time(current, true); \
> preempt_count_sub(HARDIRQ_OFFSET); \
> } while (0)
>
> diff --git a/include/linux/vtime.h b/include/linux/vtime.h
> index 2cdeca0..294188ae1 100644
> --- a/include/linux/vtime.h
> +++ b/include/linux/vtime.h
> @@ -98,21 +98,21 @@ static inline void vtime_flush(struct task_struct *tsk) { }
>
>
> #ifdef CONFIG_IRQ_TIME_ACCOUNTING
> -extern void irqtime_account_irq(struct task_struct *tsk);
> +extern void irqtime_account_irq(struct task_struct *tsk, bool hardirq);
> #else
> -static inline void irqtime_account_irq(struct task_struct *tsk) { }
> +static inline void irqtime_account_irq(struct task_struct *tsk, bool hardirq) { }
> #endif
>
> -static inline void account_irq_enter_time(struct task_struct *tsk)
> +static inline void account_irq_enter_time(struct task_struct *tsk, bool hardirq)
> {
> vtime_account_irq_enter(tsk);
> - irqtime_account_irq(tsk);
> + irqtime_account_irq(tsk, hardirq);
> }
>
> -static inline void account_irq_exit_time(struct task_struct *tsk)
> +static inline void account_irq_exit_time(struct task_struct *tsk, bool hardirq)
> {
> vtime_account_irq_exit(tsk);
> - irqtime_account_irq(tsk);
> + irqtime_account_irq(tsk, hardirq);
> }
>
> #endif /* _LINUX_KERNEL_VTIME_H */
> diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> index 5a55d23..166f1d7 100644
> --- a/kernel/sched/cputime.c
> +++ b/kernel/sched/cputime.c
> @@ -47,7 +47,7 @@ static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
> * Called before incrementing preempt_count on {soft,}irq_enter
> * and before decrementing preempt_count on {soft,}irq_exit.
> */
> -void irqtime_account_irq(struct task_struct *curr)
> +void irqtime_account_irq(struct task_struct *curr, bool hardirq)
> {
> struct irqtime *irqtime = this_cpu_ptr(&cpu_irqtime);
> s64 delta;
> @@ -68,7 +68,7 @@ void irqtime_account_irq(struct task_struct *curr)
> */
> if (hardirq_count())
> irqtime_account_delta(irqtime, delta, CPUTIME_IRQ);
> - else if (in_serving_softirq() && curr != this_cpu_ksoftirqd())
> + else if (in_serving_softirq() && curr != this_cpu_ksoftirqd() && !hardirq)
> irqtime_account_delta(irqtime, delta, CPUTIME_SOFTIRQ);
> }
In my opinion, we don't need to use the hardirq flag, the code: if
(hardirq_count())
already tell us that where the delt time is from.
Thanks
> EXPORT_SYMBOL_GPL(irqtime_account_irq);
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index bf88d7f6..da59ea39 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -270,7 +270,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
> current->flags &= ~PF_MEMALLOC;
>
> pending = local_softirq_pending();
> - account_irq_enter_time(current);
> + account_irq_enter_time(current, false);
>
> __local_bh_disable_ip(_RET_IP_, SOFTIRQ_OFFSET);
> in_hardirq = lockdep_softirq_start();
> @@ -321,7 +321,7 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
> }
>
> lockdep_softirq_end(in_hardirq);
> - account_irq_exit_time(current);
> + account_irq_exit_time(current, false);
> __local_bh_enable(SOFTIRQ_OFFSET);
> WARN_ON_ONCE(in_interrupt());
> current_restore_flags(old_flags, PF_MEMALLOC);
> @@ -417,7 +417,7 @@ static inline void __irq_exit_rcu(void)
> #else
> lockdep_assert_irqs_disabled();
> #endif
> - account_irq_exit_time(current);
> + account_irq_exit_time(current, true);
> preempt_count_sub(HARDIRQ_OFFSET);
> if (!in_interrupt() && local_softirq_pending())
> invoke_softirq();
> --
> 2.7.5
>
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