On Fri, Nov 1, 2024 at 6:06 PM Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>
> On Fri, Nov 01, 2024 at 11:17:47AM +0800, Yafang Shao wrote:
> > Since CPU time accounting is a performance-critical path, let's define
> > sched_clock_irqtime as a static key to minimize potential overhead.
> >
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > ---
> > kernel/sched/cputime.c | 16 +++++++---------
> > kernel/sched/sched.h | 1 +
> > 2 files changed, 8 insertions(+), 9 deletions(-)
> >
> > diff --git a/kernel/sched/cputime.c b/kernel/sched/cputime.c
> > index 0bed0fa1acd9..d0b6ea737d04 100644
> > --- a/kernel/sched/cputime.c
> > +++ b/kernel/sched/cputime.c
> > @@ -7,6 +7,8 @@
> > #include <asm/cputime.h>
> > #endif
> >
> > +DEFINE_STATIC_KEY_FALSE(sched_clock_irqtime);
> > +
> > #ifdef CONFIG_IRQ_TIME_ACCOUNTING
> >
> > /*
> > @@ -22,16 +24,14 @@
> > */
> > DEFINE_PER_CPU(struct irqtime, cpu_irqtime);
> >
> > -static int sched_clock_irqtime;
> > -
> > void enable_sched_clock_irqtime(void)
> > {
> > - sched_clock_irqtime = 1;
> > + static_branch_enable(&sched_clock_irqtime);
> > }
> >
> > void disable_sched_clock_irqtime(void)
> > {
> > - sched_clock_irqtime = 0;
> > + static_branch_disable(&sched_clock_irqtime);
> > }
> >
> > static void irqtime_account_delta(struct irqtime *irqtime, u64 delta,
> > @@ -57,7 +57,7 @@ void irqtime_account_irq(struct task_struct *curr, unsigned int offset)
> > s64 delta;
> > int cpu;
> >
> > - if (!sched_clock_irqtime)
> > + if (!static_branch_likely(&sched_clock_irqtime))
> > return;
> >
> > cpu = smp_processor_id();
> > @@ -90,8 +90,6 @@ static u64 irqtime_tick_accounted(u64 maxtime)
> >
> > #else /* CONFIG_IRQ_TIME_ACCOUNTING */
> >
> > -#define sched_clock_irqtime (0)
> > -
> > static u64 irqtime_tick_accounted(u64 dummy)
> > {
> > return 0;
>
> This makes no sense... in the IRQ_TIME_ACCOUNTING=n case you shouldn't
> be using the static key.
will change it.
--
Regards
Yafang
