linux-kernel - Re: [PATCH 13/16] time: optimize tick_setup

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Message-ID: <YtXSK7qt+TuTRIbV@worktop.programming.kicks-ass.net>
Date:   Mon, 18 Jul 2022 23:35:39 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Yury Norov <yury.norov@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Lobakin <alexandr.lobakin@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Alexey Klimov <aklimov@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ben Segall <bsegall@...gle.com>,
        Christoph Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
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        Guenter Roeck <linux@...ck-us.net>,
        Ingo Molnar <mingo@...hat.com>,
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        John Fastabend <john.fastabend@...il.com>,
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        linux-mm@...ck.org, netdev@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH 13/16] time: optimize tick_setup_device()

On Mon, Jul 18, 2022 at 12:28:41PM -0700, Yury Norov wrote:
>  kernel/time/tick-common.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
> index 7205f76f8d10..7b2da8ef09ef 100644
> --- a/kernel/time/tick-common.c
> +++ b/kernel/time/tick-common.c
> @@ -255,7 +255,7 @@ static void tick_setup_device(struct tick_device *td,
>  	 * When the device is not per cpu, pin the interrupt to the
>  	 * current cpu:
>  	 */
> -	if (!cpumask_equal(newdev->cpumask, cpumask))
> +	if (newdev->cpumask != cpumask && !cpumask_equal(newdev->cpumask, cpumask))
>  		irq_set_affinity(newdev->irq, cpumask);

This is again making a slow path harder to read for now benefit.