Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261493AbVCHXcG (ORCPT ); Tue, 8 Mar 2005 18:32:06 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262185AbVCHXaW (ORCPT ); Tue, 8 Mar 2005 18:30:22 -0500 Received: from gateway-1237.mvista.com ([12.44.186.158]:35319 "EHLO av.mvista.com") by vger.kernel.org with ESMTP id S262206AbVCHXXf (ORCPT ); Tue, 8 Mar 2005 18:23:35 -0500 Message-ID: <422E33F0.6020403@mvista.com> Date: Tue, 08 Mar 2005 15:23:28 -0800 From: George Anzinger Reply-To: george@mvista.com Organization: MontaVista Software User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4.2) Gecko/20040308 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Lee Revell CC: Andrew Morton , mingo@elte.hu, linux-kernel@vger.kernel.org Subject: Re: [PATCH] clean up FIXME in do_timer_interrupt References: <1109869828.2908.18.camel@mindpipe> <20050303164520.0c0900df.akpm@osdl.org> <1109899148.3630.5.camel@mindpipe> <42283857.9050007@mvista.com> <1109968985.6710.16.camel@mindpipe> <4228CBFB.3000602@mvista.com> <1110313644.4600.13.camel@mindpipe> In-Reply-To: <1110313644.4600.13.camel@mindpipe> 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: 1489 Lines: 41 Lee Revell wrote: > On Fri, 2005-03-04 at 12:58 -0800, George Anzinger wrote: > >>Lee Revell wrote: >> >>>On Fri, 2005-03-04 at 02:28 -0800, George Anzinger wrote: >>>The thing that brought this code to my attention is that with PREEMPT_RT >>>this happens to be the longest non-preemptible code path in the kernel. >>>On my 1.3 Ghz machine set_rtc_mmss takes about 50 usecs, combined with >>>the rest of timer irq we end up disabling preemption for about 90 usecs. >>>Unfortunately I don't have the trace anymore. >>> >>>Anyway the upshot is if we hung this off a timer it looks like we would >>>improve the worst case latency with PREEMPT_RT by almost 50%. Unless >>>there is some reason it has to be done synchronously of course. >> >>Well, it does have to be done at the right WRT the second, but I suspect we can >>hit that as well with a timer as it is hit now. Also, if we are _really_ off >>the mark, this can be defered till the next second. >> > > > Do you have a patch? Not at the moment, but I will work one up. > > Andrew merged my trivial patch to clean up the logic, but a real fix > would be better. > > Lee > -- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ - 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/