From owner-svn-src-head@FreeBSD.ORG Wed Jan 21 19:32:41 2015 Return-Path: Delivered-To: svn-src-head@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 3177BC7E; Wed, 21 Jan 2015 19:32:41 +0000 (UTC) Received: from mail-ig0-x231.google.com (mail-ig0-x231.google.com [IPv6:2607:f8b0:4001:c05::231]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id E81E81FC; Wed, 21 Jan 2015 19:32:40 +0000 (UTC) Received: by mail-ig0-f177.google.com with SMTP id h15so15516121igd.4; Wed, 21 Jan 2015 11:32:39 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:sender:in-reply-to:references:date:message-id:subject :from:to:cc:content-type; bh=1GqEDi7gEt8jQHrCYD9/Gd/oti/xFNJg3KauapIZxvA=; b=ewlT8PZUQ54KCZmke0XDebCTxLe4U1saQSDSU1l6b3aOncCDAz98rBkVAL97s+xmyJ EbLauRoZ+Oldr8piS5hTrTt4z9V+tUpS7lDy30tkSq5dk9dV33fCo4FC7KdsuJgz5my6 +H5rDWTa3yM6EaGs0RPckUQu1eZ0/G6EndyxclTzsMBWUeXAoVcYiwwHIu35IoGnG5IP +T5pNnN6harZi2vGNWckNP/YIVgh9CM50NppndaI/dE4vUcDKz+nktjFxzklp3ktyH39 MyUmzIkZUh8xohO6AfUjBpaOLLd10MY8kFr8tq2SXUXzwTrzcO4m5fw0VLKNQ3DhB2AJ B+hA== MIME-Version: 1.0 X-Received: by 10.50.107.72 with SMTP id ha8mr6787052igb.32.1421868759842; Wed, 21 Jan 2015 11:32:39 -0800 (PST) Sender: adrian.chadd@gmail.com Received: by 10.36.78.14 with HTTP; Wed, 21 Jan 2015 11:32:39 -0800 (PST) In-Reply-To: <20150121181512.GE15484@FreeBSD.org> References: <20150120075126.GA42409@kib.kiev.ua> <20150120211137.GY15484@FreeBSD.org> <54BED6FB.8060401@selasky.org> <54BEE62D.2060703@ignoranthack.me> <54BEE8E6.3080009@ignoranthack.me> <54BEEA7F.1070301@ignoranthack.me> <54BEF154.3030606@ignoranthack.me> <20150121181512.GE15484@FreeBSD.org> Date: Wed, 21 Jan 2015 11:32:39 -0800 X-Google-Sender-Auth: eF7Ur-d1yWJCVhBd7Wqt6recUB4 Message-ID: Subject: Re: svn commit: r277213 - in head: share/man/man9 sys/kern sys/ofed/include/linux sys/sys From: Adrian Chadd To: Gleb Smirnoff Content-Type: text/plain; charset=UTF-8 Cc: Hans Petter Selasky , "src-committers@freebsd.org" , "K. Macy" , Jason Wolfe , "svn-src-all@freebsd.org" , "svn-src-head@freebsd.org" , Sean Bruno , Konstantin Belousov X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 21 Jan 2015 19:32:41 -0000 On 21 January 2015 at 10:15, Gleb Smirnoff wrote: > Sean, > > On Tue, Jan 20, 2015 at 04:22:44PM -0800, Sean Bruno wrote: > S> In our universe, this commit (right or wrong) resolved our panics. I > S> think that there is some room for improvement based on the commentary > S> in this thread, but some people do indeed prefer stability over > S> performance. I hope we can come to a middle ground somewhere here. > > Sorry, but this sounds very much like alchemy. We poured this stuff > into that stuff and yield in gold precipitate. We don't understand > what's going on, but let's record the recipe into our tome of aclhemy > wisdom. > > So alchemy never came to a scientific level, and chemistry evolved > as science only when researchers started to measure, explain and > understand. > > If we treat our precious kernel in alchemy way, we will follow > the path of alchemy, except that it took centuries for alchemy to > die, and for a software product it would take a few years. > > So, for me Kip ideas sound very sensible. There could be a race > somewhere else. You tweak callout subsystem in any direction, > timings of events in kernel shift, your race is hidden. > > If we fix problems w/o understanding them, we are going alchemy way. Hi, I don't think it's quite this bad. They originally found that things were spinning for way too long. Hans found something similar and determined/concluded that the migration code in callouts was racy-by-design and dramatically simplified it and also put very hard constraints on what is a valid situation to support migrating from one callwheel to another. Now we have fallout which we can either address or back out until the callout stuff is again reviewed/fixed. I don't think it's as alchemic as is being promoted. -a