From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-1?Q?Max_M=FCller?= Subject: Re: Tweak Latency on Intel ATOM Date: Wed, 17 Feb 2010 07:26:59 +0100 Message-ID: <4B7B8C33.60800@gmx.net> References: <20100210163818.7f54ec3a@torg> <4B73B7B5.4070509@gmx.net> <20100211093447.3c0a97cd@torg> <4B7914C6.8080005@gmx.net> <20100215083847.1a4a7ef0@torg> <4B7A401A.70902@gmx.net> <20100216121858.GI9762@uudg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Clark Williams , linux-rt-users@vger.kernel.org To: "Luis Claudio R. Goncalves" Return-path: Received: from mo-p05-ob.rzone.de ([81.169.146.182]:46711 "EHLO mo-p05-ob.rzone.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933769Ab0BQG07 (ORCPT ); Wed, 17 Feb 2010 01:26:59 -0500 In-Reply-To: <20100216121858.GI9762@uudg.org> Sender: linux-rt-users-owner@vger.kernel.org List-ID: Luis Claudio R. Goncalves schrieb: > On Tue, Feb 16, 2010 at 07:50:02AM +0100, Max M=FCller wrote: > | Clark Williams schrieb: > | >On Mon, 15 Feb 2010 10:32:54 +0100 > | >Max M=FCller wrote: > | >>>I'd say you're doing pretty good keeping under 50us. You might w= ant to > | >>>try it under a heavier load than the shell script you've been ru= nning. > | >>>If you don't want to fool with rteval, try kicking off a kernel = compile > | >>>in another window like this: > | >>> > | >>>$ while true; do make -j4 clean bzImage modules; done > | >>> > | >>>and then run cyclictest. A kernel compile with parallel jobs (-j= ) is a > | >>>good overall load of computation and I/O. > | >>> > | >>I tested now like you told me with irqbalance and cpuspeed > | >>services disabled. I hope i made the right for disabling > | >>irqbalance, i used the kernel parameter acpi_no_irqbalance. Is > | >>this correct? Unfortunately the results were nearly equal as > | >>before. > | > > | >I don't think you're going to get much better results on the Atom.= I > | >have an MSI Nettop box with the dual-core version and I saw about = the > | >same results as you. > | > > | >What sort of scheduling deadlines are you trying to meet? > | > > | >Clark > | Shorter it is better it would be :-) > | I can also live with this results, but i wanted to make sure to get > | the best out of this hardware. > |=20 > | Are you running both cores on the MSI box (maybe also with > | hyperthreading enabled) with this results? > > Oops, I have overlooked that "more than one core" detail. In this cas= e, you > have two cyclictest threads (from different executions) clashing at > priority FIFO:94. That can eventually create the latencies you see. > > I would also suggest running the test without Hyperthreading (adjusti= ng the > number of cyclictest threads) just to see if the latencies are there = in > this case. > =20 > Luis > > | In the meantime i thought also if the SMI (system management mode) > | could have a bad influence. I wrote a little userspace programm > | which disables global SMI bit of the ICH7 southbridge. But also no > | better results. > | After that i was told (thanks to Luis Claudio!) to check latency > | with the kernel module hwlat_detector. The results of this module > | was 0. I interpreted this that there is no SMI that causes the > | latency on my ATOM system. > |=20 > | Regards, > | Max > > =20 I have only the single core ATOM. Clark has the dual core box.=20 Hyperthreading must be disabled, else the maximum latency rises from=20 about 50=B5s (Hypertrhreading disabled) to about 100=B5s (Hypertrhreadi= ng=20 enabled). -- 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