From: Martin Waitz <tali@admingilde.org>
To: john stultz <johnstul@us.ibm.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC] new timeofday core subsystem (v.A1)
Date: Thu, 9 Dec 2004 08:32:33 +0100 [thread overview]
Message-ID: <20041209073233.GB4663@admingilde.org> (raw)
In-Reply-To: <1102555933.1281.301.camel@cog.beaverton.ibm.com>
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hoi :)
On Wed, Dec 08, 2004 at 05:32:13PM -0800, john stultz wrote:
> Ah, actually, you missed something. The remainder you propose above is
> in units of cycles multiplied by mult. Thus to get it back to just
> cycles, we have to divide. So:
>
> ret *= ts->mult;
> if (rem)
> *rem = (ret & (1 << ts->shift -1))/mult;
> ret >>= ts->shift;
you are of course right
> Agreed?
well, divisions are always slow and we would loose precision again.
I have another suggestion: just keep the remainder in units of
cycles*mult.
ret *= ts->mult
if (rem) {
ret += *rem;
*rem = ret & (1 << ts->shift -1);
}
ret >>= ts->shift
and remove the offset_base adjustion below.
--
Martin Waitz
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next prev parent reply other threads:[~2004-12-09 7:32 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-08 1:55 [RFC] New timeofday proposal (v.A1) john stultz
2004-12-08 1:56 ` [RFC] new timeofday core subsystem (v.A1) john stultz
2004-12-08 1:57 ` [RFC] new timeofday arch specific hooks (v.A1) john stultz
2004-12-08 1:58 ` [RFC] new timeofday timesources (v.A1) john stultz
2004-12-08 2:02 ` john stultz
2004-12-08 9:17 ` [RFC] new timeofday core subsystem (v.A1) Pavel Machek
2004-12-08 18:44 ` Christoph Lameter
2004-12-08 19:22 ` john stultz
2004-12-08 18:53 ` Christoph Lameter
2004-12-08 20:27 ` Martin Waitz
[not found] ` <1102555933.1281.301.camel@cog.beaverton.ibm.com>
2004-12-09 7:32 ` Martin Waitz [this message]
2004-12-08 18:25 ` [RFC] New timeofday proposal (v.A1) Christoph Lameter
2004-12-08 19:11 ` john stultz
2004-12-08 19:20 ` Christoph Lameter
2004-12-08 19:58 ` john stultz
2004-12-08 20:14 ` Christoph Lameter
2004-12-08 21:25 ` George Anzinger
2004-12-08 23:47 ` Christoph Lameter
2004-12-08 23:36 ` john stultz
2004-12-08 23:53 ` Christoph Lameter
2004-12-09 0:17 ` john stultz
2004-12-09 0:40 ` Christoph Lameter
2004-12-09 0:51 ` john stultz
2004-12-09 1:24 ` Christoph Lameter
2004-12-09 7:57 ` Ulrich Windl
2004-12-09 8:29 ` john stultz
2004-12-09 7:47 ` Ulrich Windl
2004-12-08 18:43 ` Nicolas Pitre
2004-12-08 18:57 ` john stultz
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