Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S262148AbVCHUa0 (ORCPT ); Tue, 8 Mar 2005 15:30:26 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S262136AbVCHUaK (ORCPT ); Tue, 8 Mar 2005 15:30:10 -0500 Received: from mustang.oldcity.dca.net ([216.158.38.3]:46047 "HELO mustang.oldcity.dca.net") by vger.kernel.org with SMTP id S262047AbVCHU1Z (ORCPT ); Tue, 8 Mar 2005 15:27:25 -0500 Subject: Re: [PATCH] clean up FIXME in do_timer_interrupt From: Lee Revell To: george@mvista.com Cc: Andrew Morton , mingo@elte.hu, linux-kernel@vger.kernel.org In-Reply-To: <4228CBFB.3000602@mvista.com> 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> Content-Type: text/plain Date: Tue, 08 Mar 2005 15:27:24 -0500 Message-Id: <1110313644.4600.13.camel@mindpipe> Mime-Version: 1.0 X-Mailer: Evolution 2.0.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1301 Lines: 30 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? Andrew merged my trivial patch to clean up the logic, but a real fix would be better. Lee - 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/