linux-kernel - Re: [PATCH v2] timekeeping: get_jiffies_boot_64() for jiffies that include sleep time

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Message-ID: <CAK8P3a10PfTOhLA9d3vMTV_YXqymKLNeqCg6r7dLiNA1BwJbmA@mail.gmail.com>
Date:   Wed, 19 Jun 2019 16:41:00 +0200
From:   Arnd Bergmann <arnd@...db.de>
To:     "Jason A. Donenfeld" <Jason@...c4.com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2] timekeeping: get_jiffies_boot_64() for jiffies that
 include sleep time

On Wed, Jun 19, 2019 at 4:24 PM Jason A. Donenfeld <Jason@...c4.com> wrote:
>
> This enables using the usual get_jiffies_64() but taking into account
> time spent sleeping, giving the high performance characteristics of
> querying jiffies without the drawback.

Can you quantify how much this gains you over ktime_get_coarse_boottime
in practice? You are effectively adding yet another abstraction for time,
which is something I'd hope to avoid unless you have a strong reason other
than it being faster in theory.

How often do you read the current time?

      Arnd