Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758064AbZA2NnJ (ORCPT ); Thu, 29 Jan 2009 08:43:09 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752981AbZA2Nm4 (ORCPT ); Thu, 29 Jan 2009 08:42:56 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:53150 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752789AbZA2Nm4 (ORCPT ); Thu, 29 Jan 2009 08:42:56 -0500 Date: Thu, 29 Jan 2009 14:42:24 +0100 From: Ingo Molnar To: Peter Zijlstra Cc: Andrew Morton , Steven Rostedt , linux-kernel@vger.kernel.org, rusty@rustcorp.com.au, npiggin@suse.de, torvalds@linux-foundation.org, tglx@linutronix.de, arjan@infradead.org Subject: Re: [PATCH] use per cpu data for single cpu ipi calls Message-ID: <20090129134224.GH24391@elte.hu> References: <200901290955.38940.rusty@rustcorp.com.au> <20090128173039.cbc29e81.akpm@linux-foundation.org> <1233218954.7835.11.camel@twins> <20090129111330.GB30738@elte.hu> <1233229316.4495.39.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1233229316.4495.39.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 Content-Length: 1229 Lines: 31 * Peter Zijlstra wrote: > On Thu, 2009-01-29 at 12:13 +0100, Ingo Molnar wrote: > > * Peter Zijlstra wrote: > > > > > > Can generic_smp_call_function_single_interrupt() ever see > > > > CSD_FLAG_ALLOC set now? If not, that kfree can go away. > > > > > > Like said above, removing that kmalloc will hurt people. > > > > the whole promise of generic-IPI seems to dwindle and we'll get back to > > roughly where we started out from. > > I'd not go that far, the per-cpu csd is a nice fallback, but removing > that kmalloc is just silly. > > And I see no reason why arch specific could do any better (aside from > sparc which has fancy ipis). well if the hw can embedd at least 64 bit of dataload in the IPI itself, we could get rid of a lot of complications. But since we cannot (on x86 and most other architectures), we've got to demultiplex from generic data which brings up serialization issues and adds overhead . 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/