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

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Message-ID: <87a6zqxrqb.fsf@nanos.tec.linutronix.de>
Date:   Thu, 23 Jul 2020 15:53:32 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Anna-Maria Behnsen <anna-maria@...utronix.de>
Subject: Re: [PATCH] timers: Recalculate next timer interrupt only when necessary

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 :)

> 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.

>  	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?

Thanks,

        tglx