From mboxrd@z Thu Jan 1 00:00:00 1970 From: Venkat Subbiah Subject: Re: task switch from net-rx to idle when there is napi processing to be done Date: Wed, 25 Jan 2012 03:40:45 -0800 Message-ID: <4F1FEA3D.2080604@caviumnetworks.com> References: <4F1F6B66.5010005@caviumnetworks.com> <20120125085523.GG6305@pengutronix.de> <1327483093.6973.10.camel@marge.simson.net> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: =?UTF-8?B?VXdlIEtsZWluZS1Lw7ZuaWc=?= , "Subbiah, Venkat" , RT To: Mike Galbraith Return-path: Received: from mail3.caviumnetworks.com ([12.108.191.235]:8997 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750833Ab2AYLlT (ORCPT ); Wed, 25 Jan 2012 06:41:19 -0500 In-Reply-To: <1327483093.6973.10.camel@marge.simson.net> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 01/25/2012 01:18 AM, Mike Galbraith wrote: > On Wed, 2012-01-25 at 09:55 +0100, Uwe Kleine-K=C3=B6nig wrote: >> Hello, >> >> On Tue, Jan 24, 2012 at 06:39:34PM -0800, Venkat Subbiah wrote: >>> In the process of debugging a napi ethernet driver performance >>> issue, what I am noticing is >>> >>> 1. While the driver is in the middle of a napi packet processing >>> loop, there is a task switch from >>> sirq-net-rx to idle even though there is pending napi processing to= be done. >> I didn't check your logs below, but maybe this is related to the def= ault >> settings in /proc/sys/kernel/sched_rt_period_us and >> /proc/sys/kernel/sched_rt_runtime_us? That is 0.05s per second is >> reserved for non-RT tasks tasks such that a run-away realtime proces= s >> will not lock up the machine. >> >> To verify that, try >> >> echo -1> /proc/sys/kernel/sched_rt_runtime_us > Hm, makes sense if this is a UP box. SMP would just go borrow a cup = of > runtime from a neighbor. Yes this experiment was when running with only one core. > -Mike > > -- To unsubscribe from this list: send the line "unsubscribe linux-rt-user= s" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html