From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762375AbXEJVT3 (ORCPT ); Thu, 10 May 2007 17:19:29 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755080AbXEJVTX (ORCPT ); Thu, 10 May 2007 17:19:23 -0400 Received: from mail.tmr.com ([64.65.253.246]:33067 "EHLO gaimboi.tmr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754015AbXEJVTW (ORCPT ); Thu, 10 May 2007 17:19:22 -0400 Message-ID: <46438C54.20101@tmr.com> Date: Thu, 10 May 2007 17:19:16 -0400 From: Bill Davidsen User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.8.0.8) Gecko/20061105 SeaMonkey/1.0.6 MIME-Version: 1.0 Newsgroups: gmane.linux.kernel To: Lee Revell CC: Linux Kernel mailing List Subject: Re: Preempt of BKL and with tickless systems References: <4640E64D.3070304@tmr.com> <75b66ecd0705081701n414c29f7r74b0e4836798393a@mail.gmail.com> In-Reply-To: <75b66ecd0705081701n414c29f7r74b0e4836798393a@mail.gmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Lee Revell wrote: > On 5/8/07, Bill Davidsen wrote: >> I think I have a reasonable grip on the voluntary and full preempt >> models, can anyone give me any wisdom on the preempt of the BKL? I know >> what it does, the question is where it might make a difference under >> normal loads. Define normal as servers and desktops. > > This was introduced by Ingo to solve a real problem that I found, > where some codepath would hold the BKL for long enough to introduce > excessive scheduling latencies - search list archive for details. But > I don't remember the code path (scrolling the FB console? VT > switching? reiser3? misc. ioctl()s?). Basically, taking the BKL > disabled preemption which caused long latencies. > > It's certainly possible that whatever issue led to this was solved in > another way since. > Anything is possible. I feel that using voluntary + bkl is probably good for most servers, forced preempt for desktop, although it really doesn't seem to do much beyond voluntary. Thanks for the clarification. -- Bill Davidsen "We have more to fear from the bungling of the incompetent than from the machinations of the wicked." - from Slashdot