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 03:30:51 -0800 Message-ID: <4F1FE7EB.3030601@caviumnetworks.com> References: <4F1F6B66.5010005@caviumnetworks.com> <20120125085523.GG6305@pengutronix.de> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: "Subbiah, Venkat" , RT To: =?ISO-8859-1?Q?Uwe_Kleine-K=F6nig?= Return-path: Received: from mail3.caviumnetworks.com ([12.108.191.235]:8745 "EHLO mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751614Ab2AYLbp (ORCPT ); Wed, 25 Jan 2012 06:31:45 -0500 In-Reply-To: <20120125085523.GG6305@pengutronix.de> Sender: linux-rt-users-owner@vger.kernel.org List-ID: On 01/25/2012 12:55 AM, Uwe Kleine-K=F6nig 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 defa= ult > 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 process > will not lock up the machine. > > To verify that, try > > echo -1> /proc/sys/kernel/sched_rt_runtime_us > > . Thanks for you response. That was it. Setting this to -1 does the expec= ted. Then I tried playing with these settings and set /proc/sys/kernel/sched_rt_runtime_us to 95000 /proc/sys/kernel/sched_rt_period_us to 100000 And even with the switch from sirq-net-rx to idle happens every second= s=20 and stays in idle for 0.05 seconds. Are they any restrictions on what=20 these can be set to? I guess these setting may not be reasonable. I did= =20 verify by doing a cat of these files and read back the expected values. Then I tried /proc/sys/kernel/sched_rt_period_us to 1000000 /proc/sys/kernel/sched_rt_runtime_us to 980000 Even here the idle is for 0.05 seconds > Best regards > Uwe > -- 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