Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739AbbDOWRV (ORCPT ); Wed, 15 Apr 2015 18:17:21 -0400 Received: from 251.110.2.81.in-addr.arpa ([81.2.110.251]:43877 "EHLO lxorguk.ukuu.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755665AbbDOWRO (ORCPT ); Wed, 15 Apr 2015 18:17:14 -0400 Date: Wed, 15 Apr 2015 23:16:38 +0100 From: One Thousand Gnomes To: Linus Torvalds Cc: Greg Kroah-Hartman , Steven Rostedt , Jiri Kosina , Al Viro , Borislav Petkov , Andy Lutomirski , Andrew Morton , Arnd Bergmann , "Eric W. Biederman" , Tom Gundersen , "linux-kernel@vger.kernel.org" , Daniel Mack , David Herrmann , Djalal Harouni Subject: Re: [GIT PULL] kdbus for 4.1-rc1 Message-ID: <20150415231638.26e14f18@lxorguk.ukuu.org.uk> In-Reply-To: References: Organization: Intel Corporation X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.27; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1456 Lines: 33 On Wed, 15 Apr 2015 11:28:58 -0700 Linus Torvalds wrote: > On Wed, Apr 15, 2015 at 11:18 AM, Linus Torvalds > wrote: > > > > I've seen this claimed, but I have never seen any actual numbers. What > > speeds up? By how much? is it actually measurable? > > And just to clarify: by "what speeds up, and by how much", I do _not_ > mean "sending a dbus message speeds up by 10x and avoids context > switches". I've seen _those_ numbers. But does it actually matter? In the desktop case some of the desktop folks manage to get themselves to the point they send so many messages that it does. That's rather a reflection on people programming performance critical code armed with tools that are too easy to use combined with the fact that messaging is hard to understand and model latency-wise. There is a better way to fix those. For MPI and some of the 'we used to run on an RT nano-kernel' people then kdbus as proposed won't help - but they do have problems where (particularly on very slow processors) Linux is naturally enough not that comparable with a minimally memory protecting rtos doing atomic swaps on pointers in a shared memory. Alan -- 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/