Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755060Ab0LDWkh (ORCPT ); Sat, 4 Dec 2010 17:40:37 -0500 Received: from smtp1.linux-foundation.org ([140.211.169.13]:39863 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754605Ab0LDWkg convert rfc822-to-8bit (ORCPT ); Sat, 4 Dec 2010 17:40:36 -0500 MIME-Version: 1.0 In-Reply-To: References: <1289783580.495.58.camel@maggy.simson.net> <1289811438.2109.474.camel@laptop> <1289820766.16406.45.camel@maggy.simson.net> <1289821590.16406.47.camel@maggy.simson.net> <20101115125716.GA22422@redhat.com> <1289856350.14719.135.camel@maggy.simson.net> <20101116130413.GA29368@redhat.com> <1289917109.5169.131.camel@maggy.simson.net> <20101116150319.GA3475@redhat.com> <1289922108.5169.185.camel@maggy.simson.net> <20101116172804.GA9930@elte.hu> <1290281700.28711.9.camel@maggy.simson.net> From: Linus Torvalds Date: Sat, 4 Dec 2010 14:39:40 -0800 Message-ID: Subject: Re: [PATCH v4] sched: automated per session task groups To: Colin Walters Cc: Mike Galbraith , Ingo Molnar , Oleg Nesterov , Peter Zijlstra , Markus Trippelsdorf , Mathieu Desnoyers , LKML Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3053 Lines: 71 On Sat, Dec 4, 2010 at 12:01 PM, Colin Walters wrote: > > But then again here's a Berkeley "Unix Tutorial" that does cover it: > http://people.ischool.berkeley.edu/~kevin/unix-tutorial/section13.html What part of "nobody does that" didn't you understand? I know about "nice". I think it was part of the original Unix course I ever took, and it probably made more sense back then (sixteen people at a time on a microvax, compiling stuff). And I never used it, afaik. Nor does really anybody else. But hey, whatever floats your boat. You can use it. And you can feel special and better than the rest of us exactly because you know you really _are_ special. > Hmm...how many threads are we talking about here? ?If it's just say > one per core, then I doubt it needs nicing. I think git defaults to a maximum of 20 for it. Remember: it's not about "cores". It's about IO, and then 20 is a "let's not mess up everybody else _too_ much when we're actually CPU-bound". But that's not the point. The point is that "nice" is totally the wrong thing to do. It's _always_ the wrong thing to do. The only reason it's in tutorials and taught in intro Unix classes is that it's the only thing there is in traditional unix. And we can be better. We don't need to be stupid and traditional. But you go right on and use it. Nobody stops you. > Sure...though I imagine for "most" people that's totally I/O bound > (either on ext4 journal or hard disk seeks). Sure. And "most" people do something totally different. What's your point? The fact is, the session-based group scheduling really does work. It works on a lot of different loads. It's nice for things like my use, but it's _also_ nice for things like me ssh'ing into my kids or wife's computers to update their kernel. And it's nice for things like "make -j test" for git etc. And it doesn't hurt you. If you're happy with "nice", go on and use it. Why are you even discussing it? I'm telling you the FACT that others aren't happy with nice, and that smart people consider nice to be totally useless. But none of that means that you can't go on using it. Comprende? > # firefox & ? ? # Launch firefox and move it to "browser" group > > As soon as you do that from the same terminal that you're going to > launch the "make" from, you're back to total lossage. "Mommy mommy, it hurts when I stick forks in my eyes!" What's your point again? It's a heuristic. It works great for the cases many normal people have. If you have a graphical desktop, most sane people would tend to start the browser from that nice big browser icon. But again, if you want to stick forks in your eyes, go right ahead. It's not _my_ problem. And similarly, it's not _your_ problem if other people want to do saner things, is it? Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/