From owner-freebsd-performance@FreeBSD.ORG  Sun Jun 14 12:39:39 2009
Return-Path: <owner-freebsd-performance@FreeBSD.ORG>
Delivered-To: freebsd-performance@freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34])
	by hub.freebsd.org (Postfix) with ESMTP id E5DE11065673;
	Sun, 14 Jun 2009 12:39:39 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Received: from kennaway-macbookpro.config (freefall.freebsd.org
	[IPv6:2001:4f8:fff6::28])
	by mx1.freebsd.org (Postfix) with ESMTP id 37A1B8FC1C;
	Sun, 14 Jun 2009 12:39:38 +0000 (UTC)
	(envelope-from kris@FreeBSD.org)
Message-ID: <4A34EF89.10107@FreeBSD.org>
Date: Sun, 14 Jun 2009 13:39:37 +0100
From: Kris Kennaway <kris@FreeBSD.org>
User-Agent: Thunderbird 2.0.0.21 (Macintosh/20090302)
MIME-Version: 1.0
To: John Baldwin <jhb@freebsd.org>
References: <200904270150.31912.pieter@degoeje.nl>	<7d6fde3d0904261927s1a67cf85jc982c1a68e30e081@mail.gmail.com>
	<200904300846.41576.jhb@freebsd.org>
In-Reply-To: <200904300846.41576.jhb@freebsd.org>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Cc: acpi <acpi@freebsd.org>, freebsd-hackers@freebsd.org,
	freebsd-acpi@freebsd.org, Pieter de Goeje <pieter@degoeje.nl>,
	Garrett Cooper <yanefbsd@gmail.com>, freebsd-performance@freebsd.org
Subject: Re: ACPI-fast default timecounter, but HPET 83% faster
X-BeenThere: freebsd-performance@freebsd.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: Performance/tuning <freebsd-performance.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-performance>
List-Post: <mailto:freebsd-performance@freebsd.org>
List-Help: <mailto:freebsd-performance-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-performance>,
	<mailto:freebsd-performance-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Sun, 14 Jun 2009 12:39:40 -0000

John Baldwin wrote:
> On Sunday 26 April 2009 10:27:42 pm Garrett Cooper wrote:
>> I'm seeing similar results.
>>
>> [root@orangebox /usr/home/gcooper]# dmesg | grep 'Timecounter "'
>> Timecounter "i8254" frequency 1193182 Hz quality 0
>> Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
>> Timecounter "HPET" frequency 14318180 Hz quality 900
>> [root@orangebox /usr/home/gcooper]# ./cgt
>> 1369355
>> [root@orangebox /usr/home/gcooper]# sysctl
>> kern.timecounter.hardware="ACPI-fast"
>> kern.timecounter.hardware: HPET -> ACPI-fast
>> [root@orangebox /usr/home/gcooper]# ./cgt
>> 772289
>>
>> Why's the default ACPI-fast? For power-saving functionality or because
>> of the `quality' factor? What is the criteria that determines the
>> `quality' of a clock as what's being reported above (I know what
>> determines the quality of a clock visually from a oscilloscope =])?
> 
> I suspect that the quality of the HPET driver is lower simply because no one
> had measured it previously and HPET is newer and less "proven".
> 

 From memory, HPET was massively slower on some of the AMD test hardware 
I was using.  There was a thread about it on one of the mailing lists, 
but I can't find it right now.

Kris