From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Tue, 29 Jul 2003 12:51:30 -0600 From: Grant Grundler To: Matthew Wilcox Cc: Carlos O'Donell , parisc-linux@parisc-linux.org Subject: Re: [parisc-linux] Generic light-weight syscall. Message-ID: <20030729185130.GA22989@dsl2.external.hp.com> References: <20030725063739.GA13017@systemhalted> <20030725113700.GH1485@parcelfarce.linux.theplanet.co.uk> <20030726174845.GF31744@systemhalted> <20030726180031.GG31744@systemhalted> <20030727122745.GC16753@dsl2.external.hp.com> <20030728155703.GA32553@systemhalted> <20030728174551.GC3840@parcelfarce.linux.theplanet.co.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20030728174551.GC3840@parcelfarce.linux.theplanet.co.uk> 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 Mon, Jul 28, 2003 at 06:45:51PM +0100, Matthew Wilcox wrote: ... > > It might be too costly to do the sync'ing all the time, and too costly > > for a fast gettimeofday to do a sync at the polling point. If they all use the same clock source they won't drift. > > gettimeofday. Do we even have such a fast clock on PA? What is the > > fastest clock across the most boxes? cr16 > You know, you don't even need kernel help for this. According to page > 2-5 of the Kane book, the Interval Timer is accessible by non-privileged > instructions. One needs kernel help in determining the difference between CPUs and handling CR16 rollover (mostly a problem for 32-bit machines). But then user space can read CR16 and "normalize" the time. grant