From mboxrd@z Thu Jan 1 00:00:00 1970 References: <574D9B03.8080706@sigmatek.at> <20160531141646.GG5951@hermes.click-hack.org> <574EE886.2020907@sigmatek.at> <20160601141238.GC14103@hermes.click-hack.org> From: Wolfgang Netbal Message-ID: <574FEB2D.5010509@sigmatek.at> Date: Thu, 2 Jun 2016 10:15:41 +0200 MIME-Version: 1.0 In-Reply-To: <20160601141238.GC14103@hermes.click-hack.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Xenomai] Performance impact after switching from 2.6.2.1 to 2.6.4 Reply-To: wolfgang.netbal@sigmatek.at List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: xenomai@xenomai.org Am 2016-06-01 um 16:12 schrieb Gilles Chanteperdrix: > On Wed, Jun 01, 2016 at 03:52:06PM +0200, Wolfgang Netbal wrote: >> >> Am 2016-05-31 um 16:16 schrieb Gilles Chanteperdrix: >>> On Tue, May 31, 2016 at 04:09:07PM +0200, Wolfgang Netbal wrote: >>>> Dear all, >>>> >>>> we have moved our application from "XENOMAI 2.6.2.1 + Linux 3.0.43" to >>>> "XENOMAI 2.6.4. + Linux 3.10.53". Our target is an i.MX6DL. The system >>>> is now up and running and works stable. Unfortunately we see a >>>> difference in the performance. Our old combination (XENOMAI 2.6.2.1 + >>>> Linux 3.0.43) was slightly faster. >>>> >>>> At the moment it looks like that XENOMAI 2.6.4 calls >>>> xnpod_schedule_handler much more often then XENOMAI 2.6.2.1 in our old >>>> system. Every call of xnpod_schedule_handler interrupts our main >>>> XENOMAI task with priority = 95. >>>> >>>> I have compared the configuration of both XENOMAI versions but did not >>>> found any difference. I checked the source code (new commits) but did >>>> also not find a solution. >>> Have you tried Xenomai 2.6.4 with Linux 3.0.43 ? In order to see >>> whether it comes from the kernel update or the Xenomai udpate? >> I've tried Linux 3.0.43 with Xenomai 2.6.4 an there is no difference to >> Xenomai 2.6.2.1 >> Looks like there is an other reason than Xenomai. > Ok, one thing to pay attention to on imx6 is the L2 cache write > allocate policy. You want to disable L2 write allocate on imx6 to > get low latencies. I do not know which patches exactly you are > using, so it is difficult to check, but the kernel normally displays > the value set in the L2 auxiliary configuration register, you can > check in the datasheet if it means that L2 write allocate is > disabled or not. And check if you get the same value with 3.0 and > 3.10. Thank you for this hint, I looked around in the kernel config, but cant find an option sounds like L2 write allocate. The only option I found was CACHE_L2X0 and that is activated on both kernels. Do you have an idea whats the name of this configuration or where in the kernel sources it should be located, so I can find out whats the name of the config flag by searching the sourcecode.