Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S269075AbUINNhM (ORCPT ); Tue, 14 Sep 2004 09:37:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S269297AbUINNhM (ORCPT ); Tue, 14 Sep 2004 09:37:12 -0400 Received: from smtp205.mail.sc5.yahoo.com ([216.136.129.95]:58220 "HELO smtp205.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S269075AbUINNdz (ORCPT ); Tue, 14 Sep 2004 09:33:55 -0400 Message-ID: <4146F33C.9030504@yahoo.com.au> Date: Tue, 14 Sep 2004 23:33:48 +1000 From: Nick Piggin User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7.2) Gecko/20040820 Debian/1.7.2-4 X-Accept-Language: en MIME-Version: 1.0 To: Ingo Molnar CC: Andrew Morton , linux-kernel@vger.kernel.org Subject: Re: [patch] sched: fix scheduling latencies for !PREEMPT kernels References: <20040914101904.GD24622@elte.hu> <20040914102517.GE24622@elte.hu> <20040914104449.GA30790@elte.hu> <20040914105048.GA31238@elte.hu> <20040914105904.GB31370@elte.hu> <20040914110237.GC31370@elte.hu> <20040914110611.GA32077@elte.hu> <20040914112847.GA2804@elte.hu> <20040914114228.GD2804@elte.hu> <4146EA3E.4010804@yahoo.com.au> <20040914132225.GA9310@elte.hu> In-Reply-To: <20040914132225.GA9310@elte.hu> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1112 Lines: 27 Ingo Molnar wrote: > * Nick Piggin wrote: > > >>Could these ones go up a level? We break down scanning into 32 page >>chunks, so I don't think it needs to be checked every page. > > > not really - we can occasionally get into high latencies even with a > single page - if a single page is mapped by alot of processes. > So doing it in the loop doesn't really give you a deterministic maximum latency if somebody is out to cause trouble, does it? OTOH, I guess libc or some shared memory segment may be mapped into a lot of processes even on RT applictions. Another thing, I don't mean this to sound like a rhetorical question, but if we have a preemptible kernel, why is it a good idea to sprinkle cond_rescheds everywhere? Isn't this now the worst of both worlds? Why would someone who really cares about latency not enable preempt? - 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/