From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758093AbYC0KpU (ORCPT ); Thu, 27 Mar 2008 06:45:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755274AbYC0KpG (ORCPT ); Thu, 27 Mar 2008 06:45:06 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:40823 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754998AbYC0KpF (ORCPT ); Thu, 27 Mar 2008 06:45:05 -0400 Date: Thu, 27 Mar 2008 11:43:59 +0100 From: Ingo Molnar To: Jens Axboe Cc: linux-kernel@vger.kernel.org, npiggin@suse.de, paulus@samba.org, tglx@linutronix.de, mingo@redhat.com, tony.luck@intel.com, Alan.Brunelle@hp.com Subject: Re: [PATCH 0/5] Generic smp_call_function(), improvements, and smp_call_function_single() Message-ID: <20080327104359.GC26725@elte.hu> References: <1205927772-31401-1-git-send-email-jens.axboe@oracle.com> <20080321095343.GA21409@elte.hu> <20080321131558.GA15355@kernel.dk> <20080327100802.GD15003@elte.hu> <20080327103707.GH12346@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20080327103707.GH12346@kernel.dk> User-Agent: Mutt/1.5.17 (2007-11-01) 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 * Jens Axboe wrote: > I very much wanted the kthread approach to work, since it's easier to > work with. It's not for lack of will or trying... I'll be happy to > supply you otherwise identical patches for this, the only difference > being kthread of IPI completions if you want to play with this. i'd love to be able to run/pull something simple that enables me to replicate the measurements you did on a generic PC [without having to hit any real IO hardware which would put any context switching effects down into the noise category]. Obviously since the kthread approach embedds IPI sending it can never be as fast as a pure IPI approach - but it should still be reasonably fast. 3 usecs versus 2 usecs in a microbenchmark sounds about right to me, but it would be better to make it a better-sounding 2.5 usecs versus 2 usecs or so :-) Ingo