linux-kernel - Re: [PATCH 1/5] split clocksource adjustment from clockosurce mult

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Message-ID: <Pine.LNX.4.64.0803150526060.1791@scrub.home>
Date:	Sat, 15 Mar 2008 05:28:24 +0100 (CET)
From:	Roman Zippel <zippel@...ux-m68k.org>
To:	john stultz <johnstul@...ibm.com>
cc:	lkml <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH 1/5] split clocksource adjustment from clockosurce mult

Hi,

On Fri, 14 Mar 2008, john stultz wrote:

> @@ -179,7 +181,7 @@ static inline cycle_t clocksource_read(struct clocksource *cs)
>  static inline s64 cyc2ns(struct clocksource *cs, cycle_t cycles)
>  {
>  	u64 ret = (u64)cycles;
> -	ret = (ret * cs->mult) >> cs->shift;
> +	ret = (ret * (cs->mult + cs->mult_adj)) >> cs->shift;
>  	return ret;
>  }

This add an extra memory access and extra instruction to a code path, we 
should keep as short as possible.
I'd rather add a mult_raw or mult_org and use that for your next patch.

bye, Roman
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