linux-kernel - Re: [PATCH 02/10] clocksource: Simplify logic around clocksource wrapping saftey margins

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Date:	Fri, 09 Jan 2015 18:03:34 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	John Stultz <john.stultz@...aro.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
CC:	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>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH 02/10] clocksource: Simplify logic around clocksource
 wrapping saftey margins

On 01/09/2015 04:34 PM, John Stultz wrote:
> The clocksource logic has a number of places where we try to
> include a safety margin. Most of these are 12% safety margins,
> but they are inconsistently applied and sometimes are applied
> on top of each other.
>
> Additionally, in the previous patch, we corrected an issue
> where we unintentionally in effect created a 50% saftey margin,
> which these 12.5% margins where then added to.
>
> So to siplify the logic here, this patch removes the various
> 12.5% margins, and consolidates adding the margin in one place:
> clocks_calc_max_nsecs().
>
> Addtionally, Linus prefers a 50% safety margin, as it allows
> bad clock values to be more easily caught. This should really
> have no net effect, due to the corrected issue earlier which
> caused greater then 50% margins to be used w/o issue.
>
> Cc: Dave Jones <davej@...emonkey.org.uk>
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Richard Cochran <richardcochran@...il.com>
> Cc: Prarit Bhargava <prarit@...hat.com>
> Cc: Stephen Boyd <sboyd@...eaurora.org>
> Cc: Ingo Molnar <mingo@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: John Stultz <john.stultz@...aro.org>
> ---

For sched_clock.c part

Acked-by: Stephen Boyd <sboyd@...eaurora.org>

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

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