From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266210AbUGJLTB (ORCPT ); Sat, 10 Jul 2004 07:19:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266212AbUGJLTB (ORCPT ); Sat, 10 Jul 2004 07:19:01 -0400 Received: from mx1.elte.hu ([157.181.1.137]:54432 "EHLO mx1.elte.hu") by vger.kernel.org with ESMTP id S266210AbUGJLS7 (ORCPT ); Sat, 10 Jul 2004 07:18:59 -0400 Date: Sat, 10 Jul 2004 13:19:18 +0200 From: Ingo Molnar To: Elladan Cc: Peter Williams , Con Kolivas , Andrew Morton , Nick Piggin , linux kernel mailing list Subject: Re: Likelihood of rt_tasks Message-ID: <20040710111918.GB22265@elte.hu> References: <40EE6CC2.8070001@kolivas.org> <40EF2FF2.6000001@bigpond.net.au> <20040710035737.GA7552@eskimo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040710035737.GA7552@eskimo.com> User-Agent: Mutt/1.4.1i X-ELTE-SpamVersion: MailScanner 4.31.6-itk1 (ELTE 1.2) SpamAssassin 2.63 ClamAV 0.73 X-ELTE-VirusStatus: clean X-ELTE-SpamCheck: no X-ELTE-SpamCheck-Details: score=-4.9, required 5.9, autolearn=not spam, BAYES_00 -4.90 X-ELTE-SpamLevel: X-ELTE-SpamScore: -4 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Elladan wrote: > Average wall speed of RT task wakeup isn't really an issue - the issue > is deterministic worst-case latency. Adding a hundred cycles every time > won't cause someone to miss a deadline. [...] we are dealing here with about half a cycle or so overhead. (an extra jump back to the 'likely' section) Often the BTB can even totally eliminate the overhead. Worst-case we've got a slightly larger icache footprint. But all in one it's not really an issue, and if you compile for embedded it wont be done by the compiler anyway. Ingo