From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S263923AbUFXG75 (ORCPT ); Thu, 24 Jun 2004 02:59:57 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S263971AbUFXG75 (ORCPT ); Thu, 24 Jun 2004 02:59:57 -0400 Received: from mproxy.gmail.com ([216.239.56.240]:54291 "HELO mproxy.gmail.com") by vger.kernel.org with SMTP id S263923AbUFXG74 (ORCPT ); Thu, 24 Jun 2004 02:59:56 -0400 Message-ID: <7c07cd6904062323593201a558@mail.gmail.com> Date: Thu, 24 Jun 2004 12:29:55 +0530 From: abhijit To: linux-kernel@vger.kernel.org Subject: Re: do_gettimeofday( ) precision? In-Reply-To: <7c07cd6904062323437ff6ac69@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit References: <7c07cd69040623082311234157@mail.gmail.com> <7c07cd6904062323437ff6ac69@mail.gmail.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 24 Jun 2004 12:13:11 +0530, abhijit wrote: > > basically i want some counter w/ microsend resolution that fits into 32 bits. > couple of possible solutions come to my mind: > > [1] use TSC and convert it to microsec > [2] use get_timeofday( ) and convert to microsec > [3] use xtime variable directly and convert to microsec > (any other ways?) > > conversion in [1] will be costly (a div involved). > conversion in [2]/[3] can be done using bit operators. (usec|sec << 20) > but [2] will incur function call overhead which i'd like to avoid. > > so is using xtime directly ok and reliable? ok. after reading up the source, i think xtime isn;t updated frequently and will not have the required resolution :( so calling do_gettimeofday() seems the only way out (unless somebody has any other idea). btw why isn't do_gettimeofday( ) declared as "inline". so its bit cheaper to call especially where you are timestamping (say packets) often. thanks abhijit