From mboxrd@z Thu Jan 1 00:00:00 1970 From: Klaas van Gend Subject: Re: preempt rt in commercial use Date: Tue, 14 Sep 2010 12:06:32 +0200 Message-ID: <201009141206.32587.klaas.van.gend@mvista.com> References: <201009141317.13439@zigzag.lvk.cs.msu.su> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit To: "linux-rt-users" Return-path: Received: from mail-yw0-f46.google.com ([209.85.213.46]:52725 "EHLO mail-yw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752517Ab0INKGi (ORCPT ); Tue, 14 Sep 2010 06:06:38 -0400 Received: by ywh1 with SMTP id 1so2315783ywh.19 for ; Tue, 14 Sep 2010 03:06:38 -0700 (PDT) In-Reply-To: <201009141317.13439@zigzag.lvk.cs.msu.su> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Tuesday 14 September 2010 11:17:12 Nikita V. Youshchenko wrote: > > Hello > > some companies asked me to show that premmpt rt is comercially used. > > are you using it ? > > MontaVista has long supplied preempt-rt to lots of it's customers. Let me elaborate on that a little. Yes, we have a *lot* of customers using PREEMPT_RT. In my experience they fall into a few different categories: 1) using it because "it is faster". Well, I've tried to squash that idea at every customer I've been, but it's not easy to get out of their heads. In most cases, these customers have no clue why they enabled it. 2) using it because Linux was too slow otherwise. Unfortunately something I've run across a few times now - that the embedded boards are too slow to reliably grab all bytes from a serial port. Of course this has something to do with system load and bad design of serial data streams... In many cases, missing a byte can cause serious trouble, like having to do a whole sample analysis again (lab equipment). 3) using it to work around system limitations, e.g. reducing priority on less relevant interrupts and/or threads. This is the best use case. For example, if you design data acquisition or control loops, they better run reliably, with low jitter. So you want to reduce priority of everything not that relevant. Hope this helps! -- Klaas van Gend Senior Solutions Architect, MontaVista Software LLC phone: +31 40 2801386