From mboxrd@z Thu Jan 1 00:00:00 1970 References: <20160606153545.GA376@hermes.click-hack.org> <5756D673.4080408@sigmatek.at> <20160607170050.GA13922@hermes.click-hack.org> <57714C60.4070407@sigmatek.at> <20160627164604.GH18662@hermes.click-hack.org> <577235C4.2080507@sigmatek.at> <20160628083404.GI18662@hermes.click-hack.org> <57724022.8010904@sigmatek.at> <20160628091747.GK18662@hermes.click-hack.org> <57724333.6010608@sigmatek.at> <20160628092955.GL18662@hermes.click-hack.org> From: Wolfgang Netbal Message-ID: <577248AB.5070601@sigmatek.at> Date: Tue, 28 Jun 2016 11:51:39 +0200 MIME-Version: 1.0 In-Reply-To: <20160628092955.GL18662@hermes.click-hack.org> Content-Type: text/plain; charset="windows-1252"; format="flowed" Content-Transfer-Encoding: quoted-printable 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: gilles.chanteperdrix@xenomai.org Cc: xenomai@xenomai.org Am 2016-06-28 um 11:29 schrieb Gilles Chanteperdrix: > On Tue, Jun 28, 2016 at 11:28:19AM +0200, Wolfgang Netbal wrote: >> >> Am 2016-06-28 um 11:17 schrieb Gilles Chanteperdrix: >>> On Tue, Jun 28, 2016 at 11:15:14AM +0200, Wolfgang Netbal wrote: >>>> Am 2016-06-28 um 10:34 schrieb Gilles Chanteperdrix: >>>>> On Tue, Jun 28, 2016 at 10:31:00AM +0200, Wolfgang Netbal wrote: >>>>>> Am 2016-06-27 um 18:46 schrieb Gilles Chanteperdrix: >>>>>>> On Mon, Jun 27, 2016 at 05:55:12PM +0200, Wolfgang Netbal wrote: >>>>>>>> Am 2016-06-07 um 19:00 schrieb Gilles Chanteperdrix: >>>>>>>>> On Tue, Jun 07, 2016 at 04:13:07PM +0200, Wolfgang Netbal wrote: >>>>>>>>>> Am 2016-06-06 um 17:35 schrieb Gilles Chanteperdrix: >>>>>>>>>>> On Mon, Jun 06, 2016 at 09:03:40AM +0200, Wolfgang Netbal wrote: >>>>>>>>>>>> Am 2016-06-02 um 10:23 schrieb Gilles Chanteperdrix: >>>>>>>>>>>>> On Thu, Jun 02, 2016 at 10:15:41AM +0200, Wolfgang Netbal wro= te: >>>>>>>>>>>>>> Am 2016-06-01 um 16:12 schrieb Gilles Chanteperdrix: >>>>>>>>>>>>>>> On Wed, Jun 01, 2016 at 03:52:06PM +0200, Wolfgang Netbal w= rote: >>>>>>>>>>>>>>>> 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 + Li= nux 3.0.43" to >>>>>>>>>>>>>>>>>> "XENOMAI 2.6.4. + Linux 3.10.53". Our target is an i.MX6= DL. The system >>>>>>>>>>>>>>>>>> is now up and running and works stable. Unfortunately we= see a >>>>>>>>>>>>>>>>>> difference in the performance. Our old combination (XENO= MAI 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 =3D 95. >>>>>>>>>> As I wrote above, I get interrupts 1037 handled by rthal_apc_han= dler() >>>>>>>>>> and 1038 handled by xnpod_schedule_handler() while my realtime t= ask >>>>>>>>>> is running on kernel 3.10.53 with Xenomai 2.6.4. >>>>>>>>>> On kernel 3.0.43 with Xenomai 2.6.4 there are no interrupts, exc= ept the >>>>>>>>>> once that are send by my board using GPIOs, but this virtual int= errupts >>>>>>>>>> are assigned to Xenomai and Linux as well but I didn't see a han= dler >>>>>>>>>> installed. >>>>>>>>>> I'm pretty sure that these interrupts are slowing down my system= , but >>>>>>>>>> where do they come from ? >>>>>>>>>> why didn't I see them on Kernel 3.0.43 with Xenomai 2.6.4 ? >>>>>>>>>> how long do they need to process ? >>>>>>>>> How do you mean you do not see them? If you are talking about the >>>>>>>>> rescheduling API, it used no to be bound to a virq (so, it would >>>>>>>>> have a different irq number on cortex A9, something between 0 and= 31 >>>>>>>>> that would not show in the usual /proc files), I wonder if 3.0 is >>>>>>>>> before or after that. You do not see them in /proc, or you see th= em >>>>>>>>> and their count does not increase? >>>>>>>> Sorry for the long delay, we ran a lot of tests to find out what c= ould >>>>>>>> be the reason for >>>>>>>> the performance difference. >>>>>>>> >>>>>>>> If I call cat /proc/ipipe/Xenomai I dont see the IRQ handler assig= ned to >>>>>>>> the virtual >>>>>>>> IRQ on Kernel 3.0.43, but it looks like thats an issue of the Kern= el >>>>>>>>> As for where they come from, this is not a mystery, the reschedule >>>>>>>>> IPI is triggered when code on one cpu changes the scheduler state >>>>>>>>> (wakes up a thread for instance) on another cpu. If you want to >>>>>>>>> avoid it, do not do that. That means, do not share mutex between >>>>>>>>> threads running on different cpus, pay attention for timers to be >>>>>>>>> running on the same cpu as the thread they signal, etc... >>>>>>>>> >>>>>>>>> The APC virq is used to multiplex several services, which you can >>>>>>>>> find by grepping the sources for rthal_apc_alloc: >>>>>>>>> ./ksrc/skins/posix/apc.c: pse51_lostage_apc =3D rthal_apc_a= lloc("pse51_lostage_handler", >>>>>>>>> ./ksrc/skins/rtdm/device.c: rtdm_apc =3D rthal_apc_alloc("def= erred RTDM close", rtdm_apc_handler, >>>>>>>>> ./ksrc/nucleus/registry.c: rthal_apc_alloc("registry_exp= ort", ®istry_proc_schedule, NULL); >>>>>>>>> ./ksrc/nucleus/pipe.c: rthal_apc_alloc("pipe_wakeup", &xnpip= e_wakeup_proc, NULL); >>>>>>>>> ./ksrc/nucleus/shadow.c: rthal_apc_alloc("lostage_hand= ler", &lostage_handler, NULL); >>>>>>>>> ./ksrc/nucleus/select.c: xnselect_apc =3D rthal_apc_alloc(= "xnselectors_destroy", >>>>>>>>> >>>>>>>>> It would be interesting to know which of these services is trigge= red >>>>>>>>> a lot. One possibility I see would be root thread priority >>>>>>>>> inheritance, so it would be caused by mode switches. This brings = the >>>>>>>>> question: do your application have threads migrating between prim= ary >>>>>>>>> and secondary mode, do you see the count of mode switches increase >>>>>>>>> with the kernel changes, do you have root thread priority >>>>>>>>> inheritance enabled? >>>>>>>>> >>>>>>>> Here a short sum up of our tests and the results and at the end a = few >>>>>>>> questions :-) >>>>>>>> >>>>>>>> we are using a Freescale imx6dl on our hardware and upgraded our o= perating system from >>>>>>>> Freescale Kernel 3.0.43 with Xenomai 2.6.2.1 and U-Boot 2013.04 as= compiler we use GCC 4.7.2 >>>>>>>> Freescale Kernel 3.10.53 with Xenomai 2.6.4 and U-Boot 2016.01 as = compiler we use GCC 4.8.2 >>>>>>>> On both Kernels the CONFIG_SMP is set. >>>>>>>> >>>>>>>> What we see is that when we running a customer project in a Xenoma= i task with priority 95 >>>>>>>> tooks 40% of the CPU time on Kernel 3.0.43 >>>>>>>> and 47% of CPU time on Kernel 3.10.53 >>>>>>>> >>>>>>>> so the new system is slower by 7% if we sum up this to 100% CPU lo= ad we have a difference of 15% >>>>>>>> To find out what is the reason for this difference we ran the foll= owing test. >>>>>>>> We tried to get the new system faster by change some components of= the system. >>>>>>>> >>>>>>>> -Changing U-Boot on new system -> still 7% slower >>>>>>>> -Copy Kernel 3.0.43 to new system -> still 7% slower >>>>>>>> -Creating Kernel 3.0.43 with >>>>>>>> Xenomai 2.6.4 and copy it to new system -> still 7% sl= ower >>>>>>>> -Compiling the new system with >>>>>>>> old GCC version ->= still 7% slower >>>>>>>> -We also checked the settings for RAM and CPU clock -> these are e= qual >>>>>>>> >>>>>>>> It looks like that is not one of the big components, >>>>>>>> so we started to test some special functions like rt_timer_tsc() >>>>>>>> In the following example we stay for 800=B5s in the while loop and >>>>>>>> start this loop again after 200=B5s delay. >>>>>>>> The task application running this code has priotity 95. >>>>>>>> >>>>>>>> Here a simplified code snipped >>>>>>>> start =3D rt_timer_tsc(); >>>>>>>> do >>>>>>>> { >>>>>>>> current =3D rt_timer_tsc(); >>>>>>>> i++;=09 >>>>>>>> } while((current - start) < 800) >>>>>>> If your CPU is running at 1 GHz and uses the global timer as clock >>>>>>> source, the clock source runs at 500 MHz, so 800 ticks of the tsc is >>>>>>> something around 1.6 us >>>>>> Sorry I simplified the code snippet a little bit to much. >>>>>> Thats the correct code. >>>>>> >>>>>> current =3D rt_timer_tsc2ns(rt_timer_tsc()); >>>>>> >>>>>>> So, I do not really understand what you are talking about. But are >>>>>>> you sure the two kernels use the same clocksource for xenomai? >>>>>>> >>>>>>> Could you show us the result of "dmesg | grep I-pipe" with the two >>>>>>> kernels ? >>>>>> Output of Kernel 3.10.53 with Xenomai 2.6.4 >>>>>> I-pipe, 3.000 MHz clocksource >>>>>> I-pipe, 396.000 MHz clocksource >>>>>> I-pipe, 396.000 MHz timer >>>>>> I-pipe, 396.000 MHz timer >>>>>> I-pipe: head domain Xenomai registered. >>>>>> >>>>>> Output of Kernel 3.0.43 with Xenomai 2.6.2.1 >>>>>> [ 0.000000] I-pipe 1.18-13: pipeline enabled. >>>>>> [ 0.331999] I-pipe, 396.000 MHz timer >>>>>> [ 0.335720] I-pipe, 396.000 MHz clocksource >>>>>> [ 0.844016] I-pipe: Domain Xenomai registered. >>>>>> >>>>>> The controller is a imx6dl, this controller can run maximum 800MHz >>>>> Ok, so the new kernel registers two tsc emulations, could you run >>>>> the "tsc" regression test to measure the tsc latency? The two tsc >>>>> emulations have very different latencies, so the result would be >>>>> unmistakable. >>>>> >>>> Output of Kernel 3.10.53 with Xenomai 2.6.4 >>>> /usr/xenomai/bin/latency >>> This test is named "latency", not "tsc". As the different names >>> imply, they are not measuring the same thing. >>> >> Sorry for the stupied question, >> but where do I find the "tsc" test, because in folder /usr/xenomai/bin/ >> is it not located > You have millions of files on your target? Or you compiled busybox > without support for the "find" utility ? > Sorry I searched for tsc befor but didn't find any executable called "tsc" what I find is /usr/share/ghostscript and its config files and=20 /usr/bin/xtscal. I find in the xenomai sources the file tsc.c, could you please tell me what option do I have to enable that this will be build ?