From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Galbraith Subject: Re: 2.6.35 RT support roadmap Date: Fri, 13 Aug 2010 08:14:47 +0200 Message-ID: <1281680087.8870.82.camel@marge.simson.net> References: <1281638311.7093.4.camel@marge.simson.net> <4C645567.2080308@gmail.com> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Cc: Sven-Thorsten Dietrich , Xianghua Xiao , "Walzer, Frank" , "linux-rt-users@vger.kernel.org" To: jordan johnston Return-path: Received: from mailout-de.gmx.net ([213.165.64.22]:54671 "HELO mail.gmx.net" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with SMTP id S1752538Ab0HMGOc (ORCPT ); Fri, 13 Aug 2010 02:14:32 -0400 In-Reply-To: Sender: linux-rt-users-owner@vger.kernel.org List-ID: On Thu, 2010-08-12 at 23:17 -0400, jordan johnston wrote: > > Google did Android and even Palm woke up (just long enough to watch its own > > demise). > > > > The rest is history. > > > > Except of course putting the RT Kernel in Android. > > As i understand it, many Android users are using the BFS patchset, and > have been for a while. BFS pretty much does what "the end result of > using the rt-patches" accomplish, minus rtirq, spin-locks, etc. You > will get the desired > responsiveness that using RT would give you. Heh, RT kernel patch and BFS _scheduler_ patch are not even on the same planet. BFS is probably not a bad choice for a single cache machine doing soft RT. I tested it pretty heavily a while back, and it was generally pretty good. > Im pretty sure that is why Zen-kernel has a git repository "very > specifically" for android (BFS is the default kernel setting). I'm > sure there are other goodies for android in there too. > > www.zen-kernel.org > > I don't know much about the Android repo's state (as it's fairly new). > but worth a > look for your "rt-usage" (ie. performance/responsiveness) for android. > As i do not own an Android, i have not tested it, but i have talked > with people who do.. > > I'm waiting to see what 2.6.35 holds for RT.... but personally i am > using BFS and 2.6.34 with a lot of performance tuning (a good deal of > time spent analyzing/tuning) and i am yielding better results not > using the upstream rt-patches. > we will see what happens in 2.6.35/36.... It depends on what you're calling performance. A non-rt kernel absolutely will outperform the rt kernel in many respects. For instance, if your measure of performance is the time it takes to play one byte ping-pong over localhost (eg netperf TCP_RR), the rt kernel will (does) lose badly due to context switch cost between various rt middle-man threads. If your performance criteria is things like priority inversion tests, suddenly the comparison does a flipflop. -Mike