From owner-freebsd-current@FreeBSD.ORG Thu Jul 9 18:30:59 2009 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id C379910656B2; Thu, 9 Jul 2009 18:30:59 +0000 (UTC) (envelope-from serenity@exscape.org) Received: from ch-smtp01.sth.basefarm.net (ch-smtp01.sth.basefarm.net [80.76.149.212]) by mx1.freebsd.org (Postfix) with ESMTP id 7C7CF8FC0A; Thu, 9 Jul 2009 18:30:59 +0000 (UTC) (envelope-from serenity@exscape.org) Received: from c83-253-252-234.bredband.comhem.se ([83.253.252.234]:43904 helo=mx.exscape.org) by ch-smtp01.sth.basefarm.net with esmtp (Exim 4.69) (envelope-from ) id 1MOyOK-0000nU-3E; Thu, 09 Jul 2009 20:30:45 +0200 Received: from [192.168.1.5] (macbookpro [192.168.1.5]) (using TLSv1 with cipher AES128-SHA (128/128 bits)) (No client certificate requested) by mx.exscape.org (Postfix) with ESMTPSA id ED35FF9943; Thu, 9 Jul 2009 20:30:45 +0200 (CEST) Message-Id: <732354CB-8FF2-4040-8ABD-B94076551C57@exscape.org> From: Thomas Backman To: Andriy Gapon In-Reply-To: <4A563501.1090905@freebsd.org> Content-Type: text/plain; charset=US-ASCII; format=flowed; delsp=yes Content-Transfer-Encoding: 7bit Mime-Version: 1.0 (Apple Message framework v935.3) Date: Thu, 9 Jul 2009 20:30:43 +0200 References: <4A562960.3010801@freebsd.org> <4A563501.1090905@freebsd.org> X-Mailer: Apple Mail (2.935.3) X-Originating-IP: 83.253.252.234 X-Scan-Result: No virus found in message 1MOyOK-0000nU-3E. X-Scan-Signature: ch-smtp01.sth.basefarm.net 1MOyOK-0000nU-3E a65a50a0ef47b5e90be4da1910aba92f Cc: freebsd-current@freebsd.org Subject: Re: dtrace users opinion solicited (timestamps) 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: Thu, 09 Jul 2009 18:31:00 -0000 On Jul 9, 2009, at 20:20, Andriy Gapon wrote: > on 09/07/2009 21:00 Thomas Backman said the following: >> On Jul 9, 2009, at 19:31, Andriy Gapon wrote: >>> There are at least the following two alternatives: >>> >>> 1. Keep things as they are and warn users not to change CPU clock >>> frequency when >>> they use DTrace and the CPU doesn't have invariant TSC. I think that >>> this should >>> cause only minor inconveniences to a portion of DTrace users. >> Hmm, but "things as they are" causes an overflow about every 10 >> seconds, >> so the value is quite useless now (which, of course, you know about, >> having written a patch for it :) > > This is because of a deficiency in the implementation of the > formula, not because > of the formula itself. > >> Is scenario #1 after the patch (PR kern/127441 for the rest of you) >> or not? > > Yes, after the patch :) In that case, I too strongly prefer alternative #1. It keeps the timestamp *time*-based, and not tick-based (thus not breaking Solaris/ OS X etc. compatibility), for one. It also makes it a whole lot easier to actually *time* things - is it even possible for a non-kernel- programmer DTrace user to easily convert the ticks to nanoseconds somewhat accurately? I think that's as good a reason as any (the first one, that is). If ZFS is kept as compatible as possible between OSes, then so should DTrace, IMHO. Regards, Thomas