From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.goquest.com (ns1.goquest.com [12.18.108.6]) by dsl2.external.hp.com (Postfix) with SMTP id 8E9CF482E for ; Sun, 27 Jul 2003 14:47:10 -0600 (MDT) Content-Type: text/plain; charset="iso-8859-1" From: Michael S.Zick To: parisc-linux@parisc-linux.org Subject: Re: [parisc-linux] Generic light-weight syscall. Date: Sun, 27 Jul 2003 15:43:11 -0500 References: <20030725063739.GA13017@systemhalted> <20030726174845.GF31744@systemhalted> <20030726180031.GG31744@systemhalted> In-Reply-To: <20030726180031.GG31744@systemhalted> MIME-Version: 1.0 Message-Id: <03072715431101.00932@wolf686> Sender: parisc-linux-admin@lists.parisc-linux.org Errors-To: parisc-linux-admin@lists.parisc-linux.org List-Help: List-Post: List-Subscribe: , List-Id: parisc-linux developers list List-Unsubscribe: , List-Archive: On Saturday 26 July 2003 01:00 pm, Carlos O'Donell wrote: > > If you map the page and make CPU 0 update the date, then I'll write the > > userspace interface for gettimeofday. > > > > I'm not sure how we would do the check for 'do we see fast gettimeofday' > > but it might be that we include a magic value there and check for it? > > Other arches must have solved this. > > Talked to Rik Van Riel about fast gettimeofday and he indicated that > it's not doable since you can't guarantee your process will get > scheduled on another CPU whose clock is out of sync by more than X and > get negative time. Though I imagine you were talking about having one > CPU update one page with time on it... and then other CPU's read this? > LaMont notes that there is no requirement from the PA design that CPU's > clock at _exactly_ the same frequency or have monotonically incrementing > clocks at the right rate. Could you explain the idea you have a bit > more? Note - some multiple cpu hardware intentionally clocks the cpu's at slightly different rates to limit RFI generation. Not sure if any HP-PARISC machines do such clocking. Mike