linux-kernel - Re: [PATCH 1/4] ktime: add a roundup function

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Message-ID: <CALAqxLXDhe2G-7vomdMtoM=sLCavaywFZ=e5tBHa4y8=s137fg@mail.gmail.com>
Date:	Fri, 13 Nov 2015 12:11:01 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Jacob Pan <jacob.jun.pan@...ux.intel.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Len Brown <len.brown@...el.com>,
	Rafael Wysocki <rafael.j.wysocki@...el.com>,
	Eduardo Valentin <edubezval@...il.com>,
	Paul Turner <pjt@...gle.com>
Subject: Re: [PATCH 1/4] ktime: add a roundup function

On Fri, Nov 13, 2015 at 11:53 AM, Jacob Pan
<jacob.jun.pan@...ux.intel.com> wrote:
> ktime roundup function can be used to keep timer aligned and
> prevent drift for recurring timeouts.
>
> Signed-off-by: Jacob Pan <jacob.jun.pan@...ux.intel.com>
> ---
>  include/linux/ktime.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/include/linux/ktime.h b/include/linux/ktime.h
> index 2b6a204..2e293fa 100644
> --- a/include/linux/ktime.h
> +++ b/include/linux/ktime.h
> @@ -233,6 +233,16 @@ static inline ktime_t ktime_sub_us(const ktime_t kt, const u64 usec)
>
>  extern ktime_t ktime_add_safe(const ktime_t lhs, const ktime_t rhs);
>
> +static inline ktime_t ktime_roundup(ktime_t x, ktime_t y)
> +{
> +       u64 temp_tv64;
> +
> +       temp_tv64 = x.tv64 + y.tv64 - 1;
> +       temp_tv64 = div64_u64(temp_tv64, y.tv64);
> +       x.tv64 = temp_tv64 * y.tv64;
> +
> +       return x;
> +}

Could you add a comment as to what the function does, and use some
better variable names here to make it more immediately obvious what is
being done here?

Something like:
/**
 * ktime_roundup - Rounds value up to interval chunk
 * @ value: Value to be rounded up
 * @ interval: interval size to round up to
 *
 * Rounds a value up to the next higher multiple of an interval size
 */
static inline ktime ktime_roundup(ktime_t value, ktime_t interval)

thanks
-john
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