Re: [PATCH v5 3/4] sched, psi: Don't account irq time if sched_clock_irqtime is disabled

[Michal Koutný]

On Tue, Dec 03, 2024 at 11:01:41AM GMT, Michal Koutný <mkoutny@xxxxxxxx> wrote:
> On Fri, Nov 08, 2024 at 09:29:03PM GMT, Yafang Shao <laoar.shao@xxxxxxxxx> wrote:
> > sched_clock_irqtime may be disabled due to the clock source. When disabled,
> > irq_time_read() won't change over time, so there is nothing to account. We
> > can save iterating the whole hierarchy on every tick and context switch.
> > 
> > Signed-off-by: Yafang Shao <laoar.shao@xxxxxxxxx>
> > Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> > ---
> >  kernel/sched/psi.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> Reviewed-by: Michal Koutný <mkoutny@xxxxxxxx>

On second thought, similar guard may be useful in psi_show() too. Since
there's a difference between zero pressure and unmeasured pressure (it'd
fail with EOPNOTSUPP).

(How common is it actually that tsc_init fails?)

Michal

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