From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-15?Q?Max_M=FCller?= Subject: Re: Tweak Latency on Intel ATOM Date: Thu, 11 Feb 2010 08:54:29 +0100 Message-ID: <4B73B7B5.4070509@gmx.net> References: <20100210163818.7f54ec3a@torg> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: linux-rt-users@vger.kernel.org To: Clark Williams Return-path: Received: from mo-p05-ob.rzone.de ([81.169.146.181]:42306 "EHLO mo-p05-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751259Ab0BKIFf (ORCPT ); Thu, 11 Feb 2010 03:05:35 -0500 In-Reply-To: <20100210163818.7f54ec3a@torg> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Clark Williams schrieb: > On Tue, 9 Feb 2010 07:41:58 +0000 (UTC) > Max Miller wrote: > > =20 >> Hello, >> >> im am using the PREEMPT-RT patch on linux 2.6.29.6. It runs on a MSI= 965GSE >> industial board with Intel ATOM CPU (N270, 1,6GHz) and i945GSE North= bridge.=20 >> >> I got about 45=B5s as maximum and 13=B5s as average latency when hyp= erthreading is >> disabled. With enabled Hyperthreading the maximum latency increses t= o about >> 100=B5s. I measured the latency with cyclictest.=20 >> >> What can i do to get better maximum latency? Can I do somthing in th= e kernel >> configuration or are there some kernel bootoptions? Or is it still i= mpossible >> with this CPU to get better results? >> >> Thanks in advance, >> Max Miller=20 >> >> >> =20 > > Make sure you turn off any power management settings in the BIOS and > turn off the irqbalance and cpuspeed services on the Linux side. > > What cyclictest command are you using to measure latency? > > Clark > =20 I run cyclictest as follows: cyclictest -n -t3 -p99 =46or generating additional system load i run (one to several instances= ): while true; do echo "blah" > /dev/null; done & Then i watch the max. latency from the thread with the highest priority= =2E Sometimes i add the parameter '-h' to generate a history. In this=20 history i can see that the most latency times are under 20=B5s, only about 5ppm are=20 worse than 30=B5s. Am i doing this correctly? The only powersave setting in the BIOS is "Intel speedstep" which i=20 disabled. I will check with disabled "irqbalance and cpuspeed services" disabled=20 and will report later. What should the adequate max. latency on this system? -- 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