From owner-cvs-all  Mon Nov 27 21:56: 6 2000
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To: Warner Losh <imp@village.org>
Cc: Alfred Perlstein <bright@wintelcom.net>,
	"Brian F. Feldman" <green@FreeBSD.org>, cvs-committers@FreeBSD.org,
	cvs-all@FreeBSD.org
Subject: Re: cvs commit: src/usr.sbin/inetd builtins.c 
In-Reply-To: Message from Warner Losh <imp@village.org> 
   of "Mon, 27 Nov 2000 22:24:03 MST." <200011280524.WAA07413@harmony.village.org> 
From: "Brian F. Feldman" <green@FreeBSD.org>
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Date: Tue, 28 Nov 2000 00:55:53 -0500
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Warner Losh <imp@village.org> wrote:
> In message <20001126182240.A8051@fw.wintelcom.net> Alfred Perlstein writes:
> : -	if ((to.tv_usec += tv.tv_usec) >= 1000000) {
> : +	to.tv_usec += tv.tv_usec;
> : +	if (to.tv_usec >= 1000000) {
> :  		to.tv_usec -= 1000000;
> :  		to.tv_sec++;
> :  	}
> 
> Shouldn't this be
> 	if (to.tv_usec >= 1000000) {
> 		to.tv_sec += to.tv_usec / 1000000;
> 		to.tv_usec %= 1000000;
> 	}

I asked Poul-Henning the same thing with regard to similar checks in the 
kernel code.  The reply was that, although this is the "most correct" way of 
doing things, a properly done calculation of to.tv_usec + tv.tv_usec in 
this (and many other) case(s) will result in a maximum of 1999998, so at 
most one subtraction and increment will be necessary.

If it's not possible to have a higher tv_usec, you save the REALLY expensive 
divide-family instructions.

--
 Brian Fundakowski Feldman           \  FreeBSD: The Power to Serve!  /
 green@FreeBSD.org                    `------------------------------'




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