From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750708AbVHXHZL (ORCPT ); Wed, 24 Aug 2005 03:25:11 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750711AbVHXHZL (ORCPT ); Wed, 24 Aug 2005 03:25:11 -0400 Received: from ns.virtualhost.dk ([195.184.98.160]:55743 "EHLO virtualhost.dk") by vger.kernel.org with ESMTP id S1750708AbVHXHZK (ORCPT ); Wed, 24 Aug 2005 03:25:10 -0400 Date: Wed, 24 Aug 2005 09:25:02 +0200 From: Jens Axboe To: Nathan Scott Cc: Linux Kernel Subject: Re: [PATCH] blk queue io tracing support Message-ID: <20050824072501.GA27992@suse.de> References: <20050823123235.GG16461@suse.de> <20050824010346.GA1021@frodo> <20050824070809.GA27956@suse.de> <20050824171931.H4209301@wobbly.melbourne.sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20050824171931.H4209301@wobbly.melbourne.sgi.com> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Aug 24 2005, Nathan Scott wrote: > On Wed, Aug 24, 2005 at 09:08:10AM +0200, Jens Axboe wrote: > > ... > > This isn't msec precision, it's usec. sched_clock() is in ns! I already > > decided that msec is too coarse, but usec _should_ be enough. > > Right you are (I was thinking m-for-micro, not m-for-milli in my head ;) > - but still, there doesn't seem to be any reason for that divide-by-1000 > and reducing the precision in the kernel rather than in userspace, does > there? Doing it the other way means you wont ever have to worry about > whether it is/isn't sufficient precision for all possible block devices, > and the precision the tool displays will just be a userspace decision. I was just worried about wrapping of ->time, but I did make it a 64-bit unit. So I guess we could go to nsec granularity, there should be plenty [*] of space. I'll change that too, I'll post an update version later. * I probably should not make such a statement :-) -- Jens Axboe