Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760152AbXFVWBd (ORCPT ); Fri, 22 Jun 2007 18:01:33 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754987AbXFVWBN (ORCPT ); Fri, 22 Jun 2007 18:01:13 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:53202 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754501AbXFVWBM (ORCPT ); Fri, 22 Jun 2007 18:01:12 -0400 Date: Fri, 22 Jun 2007 23:59:53 +0200 From: Ingo Molnar To: Linus Torvalds Cc: Steven Rostedt , LKML , Andrew Morton , Thomas Gleixner , Christoph Hellwig , john stultz , Oleg Nesterov , "Paul E. McKenney" , Dipankar Sarma , "David S. Miller" , matthew.wilcox@hp.com, kuznet@ms2.inr.ac.ru Subject: Re: [RFC PATCH 0/6] Convert all tasklets to workqueues Message-ID: <20070622215953.GA22917@elte.hu> References: <20070622040014.234651401@goodmis.org> <20070622204058.GA11777@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7 -2.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1693 Lines: 34 * Linus Torvalds wrote: > If the numbers say that there is no performance difference (or even > better: that the new code performs better or fixes some latency issue > or whatever), I'll be very happy. But if the numbers say that it's > worse, no amount of cleanliness really changes that. Most of the tasklet uses are in rarely used or arcane drivers - in fact none of my 10 test-boxes utilizes _any_ tasklet in any way that could even get close to mattering to performance. In other words: i just cannot test this, nor do i think that others will really test this. I.e. if we dont approach this problem in some other way, nothing will happen and Steve's patch will be stalled forever and will live in -rt forever. (which might be a correct end result too, but i'm just not giving up this easily :-) so how about the following, different approach: anyone who has a tasklet in any performance-sensitive codepath, please yell now. We'll also do a proactive search for such places. We can convert those places to softirqs, or move them back into hardirq context. Once this is done - and i doubt it will go beyond 1-2 places - we can just mass-convert the other 110 places to the lame but compatible solution of doing them in a global thread context. [ and on a similar notion, i still havent given up on seeing all BKL use gone from the kernel. I expect it to happen any decade now ;-) ] Ingo - 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/