From owner-freebsd-stable@FreeBSD.ORG  Tue Feb 22 20:52:07 2005
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To: Robert Watson <rwatson@FreeBSD.org>
In-reply-to: Your message of "Tue, 22 Feb 2005 19:56:03 GMT."
             <Pine.NEB.3.96L.1050222195429.68237B-100000@fledge.watson.org> 
Date: Tue, 22 Feb 2005 12:52:06 -0800
From: "Kevin Oberman" <oberman@es.net>
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cc: Emanuel Strobl <emanuel.strobl@gmx.net>
cc: freebsd-stable@freebsd.org
Subject: Re: HZ in RELENG_5? tcp_subr.c related 
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> Date: Tue, 22 Feb 2005 19:56:03 +0000 (GMT)
> From: Robert Watson <rwatson@FreeBSD.org>
> 
> 
> On Tue, 22 Feb 2005, Kevin Oberman wrote:
> 
> > > In RELENG_5, the default HZ for amd64 is 1000, but for all other platforms
> > > it is 100.  So amd64 users will see a ten-fold decrease in tcp_isn_tick()
> > > running, but i386 (and other) users will see no change.
> > 
> > Now that 5 is STABLE, I guess we are stuck with it, but in an era of
> > "slow" 2GHz systems, it seems like a questionable choice. I know that
> > there are a lot of folks running old hardware (like my trusty old K6),
> > but they are a minority and changing HZ is not a big deal. Why make the
> > majority live with 100 on fast systems or know enough to manually change
> > it? 
> > 
> > Has there been discussion of changing this for V6 or is there a reason I
> > missed for keeping HZ at 100 in the iX86 platforms.
> 
> In 6-CURRENT, HZ is 1000 for amd64, i386, and ia64, but 100 for other
> platforms (i.e., ppc, arm, and alpha).  I'm not opposed to merging the HZ
> change to RELENG_5 at some point, but given that occasional nits, such as
> the TCP nit, are turning up, I think it's worth waiting until after 5.4.

Let's keep STABLE stable. If there are timing issues with HZ of 1000 in
V5, we clearly would not want to change before they are resolved.
Happily, I have not see these on my faster systems and have not
increased HZ on anything < 1 GHz.

If I do see network problems, now I know another place to look, too.

Thanks!
-- 
R. Kevin Oberman, Network Engineer
Energy Sciences Network (ESnet)
Ernest O. Lawrence Berkeley National Laboratory (Berkeley Lab)
E-mail: oberman@es.net			Phone: +1 510 486-8634