From owner-freebsd-current@FreeBSD.ORG Sat Jun 2 19:41:52 2007 Return-Path: X-Original-To: current@freeBSD.org Delivered-To: freebsd-current@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id C6D4D16A46E; Sat, 2 Jun 2007 19:41:52 +0000 (UTC) (envelope-from kris@obsecurity.org) Received: from elvis.mu.org (elvis.mu.org [192.203.228.196]) by mx1.freebsd.org (Postfix) with ESMTP id B2FB313C4CB; Sat, 2 Jun 2007 19:41:52 +0000 (UTC) (envelope-from kris@obsecurity.org) Received: from obsecurity.dyndns.org (elvis.mu.org [192.203.228.196]) by elvis.mu.org (Postfix) with ESMTP id 7695B1A3C1C; Sat, 2 Jun 2007 12:43:06 -0700 (PDT) Received: from rot13.obsecurity.org (rot13.obsecurity.org [192.168.1.5]) by obsecurity.dyndns.org (Postfix) with ESMTP id 07E305129D; Sat, 2 Jun 2007 15:41:52 -0400 (EDT) Received: by rot13.obsecurity.org (Postfix, from userid 1001) id DBD1AC204; Sat, 2 Jun 2007 15:41:51 -0400 (EDT) Date: Sat, 2 Jun 2007 15:41:51 -0400 From: Kris Kennaway To: Nate Lawson Message-ID: <20070602194151.GA1604@rot13.obsecurity.org> References: <2792.1179764955@critter.freebsd.dk> <86zm3y9hg5.fsf@dwp.des.no> <4651E484.1010204@root.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4651E484.1010204@root.org> User-Agent: Mutt/1.4.2.2i Cc: Dag-Erling Sm??rgrav , Poul-Henning Kamp , Kris Kennaway , current@freeBSD.org, takawata@freeBSD.org Subject: Re: HPET vs other timers 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: Sat, 02 Jun 2007 19:41:52 -0000 On Mon, May 21, 2007 at 11:27:16AM -0700, Nate Lawson wrote: > Dag-Erling Sm??rgrav wrote: > > "Poul-Henning Kamp" writes: > >> Dag-Erling Sm??rgrav writes: > >>> "Poul-Henning Kamp" writes: > >>>> I can't rememember who raised the quality of it recently, CVS will > >>>> know. I was sceptical, because I also have systems where HPET is > >>>> slow. > >>> I did, with your approval, almost a year ago. > >> Yes, I said "try it" or something of the sort. > > > > For the record, I ran with HPET timers the entire time from HPET support > > was first committed until I finally committed that patch - about ten > > months - so I did test it to the best of my ability. > > > > DES > > Let's keep this technical. I'm fine with bumping HPET to below ACPI > timer if the hw turns out to be this much slower. > > Anyone able to speculate why though? HPET only reads 32 bits from a > memory mapped region. No locking or other requirements. ACPI_timer > does multiple IO ops, which according to bde@ are much slower than > memory reads. So unless something from the chipset is stopping the > processor (SMI?) when it reads from this region, I have a hard time > seeing why it's slower. I don't know what the cause is, only that it is empirically the slowest of all the timers in this workload. Can you provide supporting evidence that it is fact faster than all the alternatives in other workloads? Kris