From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755434AbYAEDZb (ORCPT ); Fri, 4 Jan 2008 22:25:31 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753211AbYAEDZW (ORCPT ); Fri, 4 Jan 2008 22:25:22 -0500 Received: from ishtar.tlinx.org ([64.81.245.74]:55170 "EHLO ishtar.tlinx.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752558AbYAEDZW (ORCPT ); Fri, 4 Jan 2008 22:25:22 -0500 Message-ID: <477EF8A4.7010507@tlinx.org> Date: Fri, 04 Jan 2008 19:25:24 -0800 From: Linda Walsh User-Agent: Thunderbird 2.0.0.9 (Windows/20071031) MIME-Version: 1.0 To: LKML Subject: general config preemption Q: preempt-model and Big-Lock Preemption Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org A question that comes to mind every time I go through the settings for "Preemption Model" and "Preempt The Big Kernel Lock". Do each of the combinations "make sense", or are some "no-ops"? For model, we have 1) no forced (server), 2) Voluntary (Desktop) 3) preemptible (low-latency Desktop), and for Big Lock Preemption (BLP), we have "yes" or "no". Questions: 1) What is the difference between "no forced" and "voluntary"? Doesn't voluntary normally mean "not forced"? 2) If a process is not preemptible, then it seems this would be "doubly so" in the kernel when the big-lock is held. So does the big-lock preemption question have any effect (when preempt-model="no forced"). 3) If a process is "fully preemptible" but "BLP=false", is that much different than "voluntary preemption" & BLP=false? I.e. -- should 'preemptible kernel' also imply "BLP=true"...i.e. _Should_ (would?) the following change be "somewhat" identical to current config options: O1) "Preempt Model"="no-forced preemption" (would set preempt-big-kern-lock to FALSE and doesn't display that question). O2) "Voluntary Preemption" (presuming there are voluntary preemption points in the kernel in places where the big-K-lock is held), then configuration would still ask whether to "Preempt The Big Kernel Lock". O3) "Preemptible model"="allow-kernel-preemption" (would set preempt-big-kern-lock to TRUE and doesn't display that question).