Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S268090AbUIPO1b (ORCPT ); Thu, 16 Sep 2004 10:27:31 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S268095AbUIPO1b (ORCPT ); Thu, 16 Sep 2004 10:27:31 -0400 Received: from mail.tmr.com ([216.238.38.203]:28164 "EHLO gatekeeper.tmr.com") by vger.kernel.org with ESMTP id S268090AbUIPO13 (ORCPT ); Thu, 16 Sep 2004 10:27:29 -0400 To: linux-kernel@vger.kernel.org Path: not-for-mail From: Bill Davidsen Newsgroups: mail.linux-kernel Subject: Re: [patch] remove the BKL (Big Kernel Lock), this time for real Date: Thu, 16 Sep 2004 10:28:08 -0400 Organization: TMR Associates, Inc Message-ID: References: <2EJTp-7bx-1@gated-at.bofh.it><2EJTp-7bx-1@gated-at.bofh.it> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Trace: gatekeeper.tmr.com 1095344426 18582 192.168.12.100 (16 Sep 2004 14:20:26 GMT) X-Complaints-To: abuse@tmr.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040803 X-Accept-Language: en-us, en In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1445 Lines: 31 Andi Kleen wrote: > Ingo Molnar writes: > > >>the attached patch is a new approach to get rid of Linux's Big Kernel >>Lock as we know it today. > > > Interesting approach. Did you measure what it does to context > switch rates? Usually adding semaphores tends to increase them > a lot. Is that (necessarily) a bad thing? If it results in less time waiting for BKL, and/or more time doing user work, that may drive throughput and responsiveness up. It depends if the time for two ctx is greater or less than the spin time on BKL. It would be nice to have the best of both worlds, use the semaphore if there is a process on the run queue, and spin if not. That sounds complex, and hopefully not worth the effort. High ctx rates are not necessarily bad, when we implemented O_DIRECT for an application the rate went up 30%, the outbound bandwidth went up 10-15%, and waitio dropped by half at peak load. As long as something useful is being done with the time previously wasted in spinning, I would expect it to be a win. -- -bill davidsen (davidsen@tmr.com) "The secret to procrastination is to put things off until the last possible moment - but no longer" -me - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/