From owner-freebsd-hackers@FreeBSD.ORG  Sun Feb 29 18:22:54 2004
Return-Path: <owner-freebsd-hackers@FreeBSD.ORG>
Delivered-To: freebsd-hackers@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id 5666816A4D0
	for <freebsd-hackers@freebsd.org>;
	Sun, 29 Feb 2004 18:22:54 -0800 (PST)
Received: from smtp3b.sentex.ca (smtp3b.sentex.ca [205.211.164.50])
	by mx1.FreeBSD.org (Postfix) with ESMTP id 0DD7543D3F
	for <freebsd-hackers@freebsd.org>;
	Sun, 29 Feb 2004 18:22:54 -0800 (PST)	(envelope-from mike@sentex.net)
Received: from avscan1.sentex.ca (avscan1.sentex.ca [199.212.134.11])
	by smtp3b.sentex.ca (8.12.10/8.12.10) with ESMTP id i212MG3Z045692;
	Sun, 29 Feb 2004 21:22:16 -0500 (EST)
	(envelope-from mike@sentex.net)
Received: from lava.sentex.ca (pyroxene.sentex.ca [199.212.134.18])
	by avscan1.sentex.ca (8.12.10/8.12.10) with ESMTP id i212Mlxa072531;
	Sun, 29 Feb 2004 21:22:48 -0500 (EST)
	(envelope-from mike@sentex.net)
Received: from simian.sentex.net ([192.168.43.27])
	by lava.sentex.ca (8.12.9p2/8.12.9) with ESMTP id i212MkZa026439;
	Sun, 29 Feb 2004 21:22:46 -0500 (EST)
	(envelope-from mike@sentex.net)
Message-Id: <6.0.3.0.0.20040229212058.05945af0@209.112.4.2>
X-Sender: mdtpop@209.112.4.2 (Unverified)
X-Mailer: QUALCOMM Windows Eudora Version 6.0.3.0
Date: Sun, 29 Feb 2004 21:23:47 -0500
To: Don Bowman <don@sandvine.com>
From: Mike Tancsa <mike@sentex.net>
In-Reply-To: <FE045D4D9F7AED4CBFF1B3B813C85337045D8328@mail.sandvine.com
 >
References: <FE045D4D9F7AED4CBFF1B3B813C85337045D8328@mail.sandvine.com>
Mime-Version: 1.0
Content-Type: text/plain; charset="us-ascii"; format=flowed
X-Virus-Scanned: by amavisd-new
cc: freebsd-hackers@freebsd.org
Subject: RE: em0, polling performance, P4 2.8ghz FSB 800mhz
X-BeenThere: freebsd-hackers@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Technical Discussions relating to FreeBSD
	<freebsd-hackers.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-hackers>
List-Post: <mailto:freebsd-hackers@freebsd.org>
List-Help: <mailto:freebsd-hackers-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-hackers>,
	<mailto:freebsd-hackers-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 01 Mar 2004 02:22:54 -0000

At 08:44 PM 29/02/2004, Don Bowman wrote:
>From: Mike Tancsa [mailto:mike@sentex.net]
> >
> > On Sat, 28 Feb 2004 23:17:44 -0500, in sentex.lists.freebsd.hackers >
> > >If you want to spend more time in kernel, perhaps change
> > >
> > >I might have HZ @ 2500 as well.
> >
> > Hi,
> >       Just curious as to the reasoning behind that ?
>
>@ high packet rates, you don't have enough DMA
>queues available to the em driver, and will drop.
>increasing the number of dma buffers will cause
>problems with cache occupancy. Increasing the HZ
>doesn't have a huge cost.

But why that value ? Did you determine it by trial and error or deduce it 
based on some other factors ?  Also, is this value optimal for fxp based boxes.

         ---Mike