From: Edgar Toernig <froese@gmx.de>
To: Sridhar Samudrala <sri@us.ibm.com>
Cc: davem@redhat.com, jgarzik@pobox.com,
linux-kernel@vger.kernel.org, netdev@oss.sgi.com
Subject: Re: [PATCH] Consolidate multiple implementations of jiffies-msecs conversions.
Date: Fri, 26 Mar 2004 21:45:07 +0100 [thread overview]
Message-ID: <20040326214507.0af7c06b.froese@gmx.de> (raw)
In-Reply-To: <Pine.LNX.4.58.0403261007370.6718@localhost.localdomain>
Sridhar Samudrala wrote:
>
> On Fri, 26 Mar 2004, Edgar Toernig wrote:
>
> > Sridhar Samudrala wrote:
> > >
> > >[...]
> > > -#define MSECS(ms) (((ms)*HZ/1000)+1)
> > > -return (((ms)*HZ+999)/1000);
> > > +return (msecs / 1000) * HZ + (msecs % 1000) * HZ / 1000;
> >
> > Did you check that all users of the new version will work correctly
> > with your rounding? Explicit round-up of delays is often required,
> > especially when talking to hardware...
>[...]
> I guess you are referring to cases when HZ < 1000(ex: 100) and msecs is
> less than 10. In those cases, the new version returns 0, whereas some of the
> older versions return 1.
Exactly - but not only <10. Any value that is not exactly representable
in jiffies. I.e. for a delay of 15ms one has to wait 2 jiffies on a 100HZ
system. Your version would give 1 jiffy = 10ms -- too short.
Ciao, ET.
prev parent reply other threads:[~2004-03-26 20:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-25 20:17 [PATCH] Consolidate multiple implementations of jiffies-msecs conversions Sridhar Samudrala
2004-03-25 20:32 ` David S. Miller
2004-03-25 20:36 ` Jeff Garzik
2004-03-25 21:05 ` Bill Rugolsky Jr.
2004-03-25 23:49 ` Sridhar Samudrala
2004-03-26 0:44 ` Edgar Toernig
2004-03-26 18:49 ` Sridhar Samudrala
2004-03-26 19:03 ` Jeff Garzik
2004-03-29 19:57 ` Sridhar Samudrala
2004-03-26 20:45 ` Edgar Toernig [this message]
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