From owner-freebsd-current@FreeBSD.ORG Sun Sep 4 19:29:04 2005 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 99E7016A41F; Sun, 4 Sep 2005 19:29:04 +0000 (GMT) (envelope-from PeterJeremy@optushome.com.au) Received: from mail12.syd.optusnet.com.au (mail12.syd.optusnet.com.au [211.29.132.193]) by mx1.FreeBSD.org (Postfix) with ESMTP id BC09F43D49; Sun, 4 Sep 2005 19:29:03 +0000 (GMT) (envelope-from PeterJeremy@optushome.com.au) Received: from cirb503493.alcatel.com.au (c220-239-19-236.belrs4.nsw.optusnet.com.au [220.239.19.236]) by mail12.syd.optusnet.com.au (8.12.11/8.12.11) with ESMTP id j84JT0LN008562 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Mon, 5 Sep 2005 05:29:01 +1000 Received: from cirb503493.alcatel.com.au (localhost.alcatel.com.au [127.0.0.1]) by cirb503493.alcatel.com.au (8.12.10/8.12.10) with ESMTP id j84JT0SR085032; Mon, 5 Sep 2005 05:29:00 +1000 (EST) (envelope-from pjeremy@cirb503493.alcatel.com.au) Received: (from pjeremy@localhost) by cirb503493.alcatel.com.au (8.12.10/8.12.9/Submit) id j84JSxFv085031; Mon, 5 Sep 2005 05:28:59 +1000 (EST) (envelope-from pjeremy) Date: Mon, 5 Sep 2005 05:28:59 +1000 From: Peter Jeremy To: Emanuel Strobl Message-ID: <20050904192858.GB77285@cirb503493.alcatel.com.au> References: <20050904011556.25064.qmail@web25407.mail.ukl.yahoo.com> <200509040427.33471@harrymail> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200509040427.33471@harrymail> User-Agent: Mutt/1.4.2i Cc: freebsd-current@freebsd.org, FreeBSD Stable Subject: Re: HZ option [Was: Re: custom kernel + if_xl + error] X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 04 Sep 2005 19:29:04 -0000 On Sun, 2005-Sep-04 04:27:24 +0200, Emanuel Strobl wrote: >standard. Here's what my non-acpi/apic system (486@133MHz) says: >kern.clockrate: { hz = 1000, tick = 1000, profhz = 1024, stathz = 128 } >And here from my 1GHz Celeron with acpi and apic: >kern.clockrate: { hz = 1000, tick = 1000, profhz = 666, stathz = 133 } > >Can somebody eplain the profhz to me? Especially why it's higher on the >much slower machine... On your older system, profhz and stathz are driven the RTC interrupts and tick is driven by the 8254. On your newer system all the clocks are derived from the LAPIC timer running at 2000Hz - tick is LAPIC/2, profhz is LAPIC/3 and stathz is LAPIC/15. The actual values of profhz and stathz are unimportant, their primary purpose is to sample the system state at a rate that is difficult for processes to synchronize with. If a process synchronizes with the profiling/statistics clock then the statistics become unreliable (and a process can cheat the scheduler by appearing to use no CPU time). -- Peter Jeremy