linux-kernel - Re: [PATCH] timers: Recalculate next timer interrupt only when necessary

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Message-ID: <20200723144544.GC28401@lenoir>
Date:   Thu, 23 Jul 2020 16:45:45 +0200
From:   Frederic Weisbecker <frederic@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: Re: [PATCH] timers: Recalculate next timer interrupt only when
 necessary

On Thu, Jul 23, 2020 at 03:53:32PM +0200, Thomas Gleixner wrote:
> Frederic Weisbecker <frederic@...nel.org> writes:
> >
> > Since recalculating the next_expiry isn't a free operation, especially
> > when we must climb up the last wheel level to find out that no timer
> > has
> 
> I'm climbing stairs or mountains :)

Arguably, climbing a wheel can be a never ending story :)

> 
> > been enqueued at all, lets reuse the next expiry cache when it is
> > known
> 
> lets? Come on, the changelog is about facts not what we might do.

Also since you applied the last patchset I have tried to quit using "we"
in the changelog and use "the code" as a subject or even the passive form.
But reading above, I did it again.

Too many habits :))

> 
> >  	unsigned long		clk;
> >  	unsigned long		next_expiry;
> > +	bool			next_expiry_recalc;
> >  	unsigned int		cpu;
> >  	bool			is_idle;
> 
> Care to stare at the output of
> 
>      pahole -C timer_base kernel/time/timer.o
> 
> before and after?

Ah right, I'll move the bool together.

Thanks.