From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752898AbZBQJon (ORCPT ); Tue, 17 Feb 2009 04:44:43 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751331AbZBQJof (ORCPT ); Tue, 17 Feb 2009 04:44:35 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:44175 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751308AbZBQJoe (ORCPT ); Tue, 17 Feb 2009 04:44:34 -0500 Date: Tue, 17 Feb 2009 10:43:59 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Linus Torvalds , Nick Piggin , Jens Axboe , "Paul E. McKenney" , Rusty Russell , Steven Rostedt , linux-kernel@vger.kernel.org, Oleg Nesterov Subject: Re: [PATCH 2/4] generic-smp: remove kmalloc usage Message-ID: <20090217094359.GA1231@elte.hu> References: <20090216163847.431174825@chello.nl> <20090216164114.521787803@chello.nl> <1234859071.4744.10.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1234859071.4744.10.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Peter Zijlstra wrote: > On Mon, 2009-02-16 at 16:40 -0800, Linus Torvalds wrote: > > > > On Mon, 16 Feb 2009, Peter Zijlstra wrote: > > > > > > Now that there is no strict need for kmalloc anymore, and nobody seems to > > > rely it for the queueing behaviour, remove it. > > > > Peter, I really hate this series. > > > > Why? > > > > In 1/4 you introduce that cfd RCU thing, and then in 2/4 you remove it > > again. > > Ah, no, I don't actually. I remove the kmalloc+call_rcu stuff in 2, not > the newly cfd mini rcu thing. > > > I realize that you seem to do that in order to do some incremental > > step-wise changes, but quite frankly, it just complicates the whole series > > and makes the patches much harder to read and follow. > > > > Why don't you just combine patches 1&2? That split-up seems to just > > confuse things. At least it confuses me. Why does it happen? > > The idea was to remove the necessity for kmalloc() in patch 1, > and then remove kmalloc() in patch 2. > > If you prefer I can fold them, no problem. > > But as you might have seen, Oleg has been punching holes in my > #1, so I guess I'm back to the drawing board no matter what > :-) I think the kmalloc() is clearly ugly, we should remove it, and if someone wants to add it we want to see _hard numbers_ that it's worth the ugliness. I.e. lets go with the two patches i posted, they are obvious and tested. We should not bend backwards trying to preserve that kmalloc() [and prove that it's safe and race-free] - i.e. the burden of proof is on the person insisting that it's needed, not on the person wanting to remove it. Ingo