linux-kernel - Re: [PATCH 2/8] cputime: Librarize per nsecs resolution cputime definitions

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Message-ID: <CAFTL4hyGBR9wmtStRNrm01g5VfKWv9mzXEq2dQh19pAZrXbd=g@mail.gmail.com>
Date:	Wed, 20 Feb 2013 17:07:15 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Kevin Hilman <khilman@...aro.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Li Zhong <zhong@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung.kim@....com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Paul Gortmaker <paul.gortmaker@...driver.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Tony Luck <tony.luck@...el.com>,
	Fenghua Yu <fenghua.yu@...el.com>,
	Nicolas Pitre <nicolas.pitre@...aro.org>
Subject: Re: [PATCH 2/8] cputime: Librarize per nsecs resolution cputime definitions

2013/2/14 Kevin Hilman <khilman@...aro.org>:
> Frederic Weisbecker <fweisbec@...il.com> writes:
>
>> The full dynticks cputime accounting that we'll soon introduce
>> will rely on sched_clock(). And its clock can have a per
>> nanosecond granularity.
>>
>> To prepare for this, we need to have a cputime_t implementation
>> that has this precision.
>>
>> ia64 virtual cputime accounting already uses that granularity
>> so all we need is to librarize its implementation in the asm
>> generic headers.
>
> ...except that for it to be truly generic (i.e. usable on 32-bit arches),
> it should be using do_div() for 64-bit divides.
>
> I understand this series is targetted at 64-bit platforms currently, but
> I'm looking (again) at getting adaptive NOHZ working on ARM, and this
> was the first obvious obstacle to even compiling.
>
> I see this is already merged into tip/sched/core, so below is a patch on
> top of that to convert to using do_div().  If you're OK with the
> approach, I'll post it formally to LKML.

Yes please, this looks like something we want.

Thanks.
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