Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266820AbUJINWF (ORCPT ); Sat, 9 Oct 2004 09:22:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266833AbUJINWF (ORCPT ); Sat, 9 Oct 2004 09:22:05 -0400 Received: from relay.pair.com ([209.68.1.20]:63499 "HELO relay.pair.com") by vger.kernel.org with SMTP id S266820AbUJINV6 (ORCPT ); Sat, 9 Oct 2004 09:21:58 -0400 X-pair-Authenticated: 66.190.53.4 Message-ID: <4167E5F5.3040700@cybsft.com> Date: Sat, 09 Oct 2004 08:21:57 -0500 From: "K.R. Foley" User-Agent: Mozilla Thunderbird 0.8 (X11/20040913) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Lee Revell CC: Con Kolivas , Ingo Molnar , linux-kernel , Rui Nuno Capela , Florian Schmidt , Mark_H_Johnson@raytheon.com, Fernando Pablo Lopez-Lezcano Subject: Re: voluntary-preempt-2.6.9-rc3-mm3-T3 References: <20040921071854.GA7604@elte.hu> <20040921074426.GA10477@elte.hu> <20040922103340.GA9683@elte.hu> <20040923122838.GA9252@elte.hu> <20040923211206.GA2366@elte.hu> <20040924074416.GA17924@elte.hu> <20040928000516.GA3096@elte.hu> <20041003210926.GA1267@elte.hu> <20041004215315.GA17707@elte.hu> <20041005134707.GA32033@elte.hu> <20041007105230.GA17411@elte.hu> <1097297824.1442.132.camel@krustophenia.net> <1097299260.1442.142.camel@krustophenia.net> In-Reply-To: <1097299260.1442.142.camel@krustophenia.net> X-Enigmail-Version: 0.86.1.0 X-Enigmail-Supports: pgp-inline, pgp-mime 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 Content-Length: 1535 Lines: 45 Lee Revell wrote: > On Sat, 2004-10-09 at 01:09, Con Kolivas wrote: > >>Lee Revell writes: >> >> >>>On Thu, 2004-10-07 at 06:52, Ingo Molnar wrote: >>> >>>>i've released the -T3 VP patch: >>>> >>>> http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.9-rc3-mm3-T3 >>>> >>> >>>With VP and PREEMPT in general, does the scheduler always run the >>>highest priority process, or do we only preempt if a SCHED_FIFO process >>>is runnable? >> >>Always the highest priority runnable. >> > > > Hmm, interesting. Would there be any advantage to a mode where only > SCHED_FIFO tasks can preempt? This seems like a much lighter way to > solve the realtime problem. > > Lee > > IMHO I don't think this gains us anything and I think that it would be a big step backward for desktop performance (any processes not scheduled RT). Not only that but I think you still have to have all of the overhead of the scheduler and the preemption points if you are going to service the RT threads. Otherwise, how do you schedule RT processes that are waiting for some I/O (that is ready) and another non-RT process is going through a code path in the kernel. The RT process now has a much worse latency. There very well may be ways to accomplish this effectively that I just don't understand. kr - 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/