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From: robert.jarzmik@free.fr (Robert Jarzmik)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH] optimize ktime_divns for constant divisors
Date: Wed, 03 Dec 2014 21:16:27 +0100	[thread overview]
Message-ID: <87zjb4zdyc.fsf@free.fr> (raw)
In-Reply-To: <alpine.LFD.2.11.1412031424150.470@knanqh.ubzr> (Nicolas Pitre's message of "Wed, 3 Dec 2014 14:43:06 -0500 (EST)")

Nicolas Pitre <nicolas.pitre@linaro.org> writes:

> Let ktime_divns() use do_div() inline whenever the divisor is constant
> and small enough.  This will make things like ktime_to_us() and 
> ktime_to_ms() much faster.

Hi Nicolas,

I suppose the "small enough" is linked to the "!(div >> 32)" in your patch.  Can
I have the rationale which brought up this value, and if that value is universal
across architectures (ie. x86/ppc/arm/...) ?

And when you say "much faster", do you have figures to add to your commit
message ?

Cheers.

--
Robert

WARNING: multiple messages have this Message-ID (diff)
From: Robert Jarzmik <robert.jarzmik@free.fr>
To: Nicolas Pitre <nicolas.pitre@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	John Stultz <john.stultz@linaro.org>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH] optimize ktime_divns for constant divisors
Date: Wed, 03 Dec 2014 21:16:27 +0100	[thread overview]
Message-ID: <87zjb4zdyc.fsf@free.fr> (raw)
In-Reply-To: <alpine.LFD.2.11.1412031424150.470@knanqh.ubzr> (Nicolas Pitre's message of "Wed, 3 Dec 2014 14:43:06 -0500 (EST)")

Nicolas Pitre <nicolas.pitre@linaro.org> writes:

> Let ktime_divns() use do_div() inline whenever the divisor is constant
> and small enough.  This will make things like ktime_to_us() and 
> ktime_to_ms() much faster.

Hi Nicolas,

I suppose the "small enough" is linked to the "!(div >> 32)" in your patch.  Can
I have the rationale which brought up this value, and if that value is universal
across architectures (ie. x86/ppc/arm/...) ?

And when you say "much faster", do you have figures to add to your commit
message ?

Cheers.

--
Robert

  parent reply	other threads:[~2014-12-03 20:16 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-12-03 19:43 [PATCH] optimize ktime_divns for constant divisors Nicolas Pitre
2014-12-03 19:43 ` Nicolas Pitre
2014-12-03 20:03 ` Arnd Bergmann
2014-12-03 20:03   ` Arnd Bergmann
2014-12-04  7:23   ` Nicolas Pitre
2014-12-04  7:23     ` Nicolas Pitre
2014-12-04 12:02     ` Arnd Bergmann
2014-12-04 12:02       ` Arnd Bergmann
2014-12-04 13:46       ` Nicolas Pitre
2014-12-04 13:46         ` Nicolas Pitre
2014-12-04 14:56         ` Arnd Bergmann
2014-12-04 14:56           ` Arnd Bergmann
2014-12-04 16:47           ` Nicolas Pitre
2014-12-04 16:47             ` Nicolas Pitre
     [not found]     ` <OF0EDEDB1C.C03829F7-ON48257DA5.00062083-48257DA5.0007628B@zte.com.cn>
2014-12-05  4:30       ` Nicolas Pitre
2014-12-05  4:30         ` Nicolas Pitre
2014-12-05 10:08         ` Arnd Bergmann
2014-12-05 10:08           ` Arnd Bergmann
2014-12-05 17:15           ` Nicolas Pitre
2014-12-05 17:15             ` Nicolas Pitre
2014-12-03 20:16 ` Robert Jarzmik [this message]
2014-12-03 20:16   ` Robert Jarzmik
2014-12-03 20:37   ` Nicolas Pitre
2014-12-03 20:37     ` Nicolas Pitre
2014-12-05 18:00 ` Nicolas Pitre
2014-12-05 18:00   ` Nicolas Pitre
2014-12-05 21:03   ` Arnd Bergmann
2014-12-05 21:03     ` Arnd Bergmann
2014-12-18 21:21     ` John Stultz
2014-12-18 21:21       ` John Stultz

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