linux-kernel - Re: [PATCH 01/12] clocksource: Simplify clocks_calc_max

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Message-ID: <20150307092020.GB30888@gmail.com>
Date:	Sat, 7 Mar 2015 10:20:20 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	John Stultz <john.stultz@...aro.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...emonkey.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Richard Cochran <richardcochran@...il.com>,
	Prarit Bhargava <prarit@...hat.com>,
	Stephen Boyd <sboyd@...eaurora.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 01/12] clocksource: Simplify clocks_calc_max_nsecs logic


* John Stultz <john.stultz@...aro.org> wrote:

> The previous clocks_calc_max_nsecs had some unecessarily
> complex bit logic to find the max interval that could cause
> multiplication overflows. Since this is not in the hot
> path, just do the divide to make it easier to read.
> 
> The previous implementation also had a subtle issue
> that it avoided overflows into signed 64bit values, where

So here you write the weird '64bit' form, while in the code you write:

> +	 * cyc2ns function without overflowing a 64-bit result.

This repeats in later patches as well. I'd suggest using '64-bit' 
consistently throughout the whole series.

> as the intervals are always unsigned. This resulted in
> overly conservative intervals, which other saftey margins
> were then added to, reducing the intended interval length.

Typo.

Thanks,

	Ingo
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