From mboxrd@z Thu Jan 1 00:00:00 1970 References: <87a6rx4c6k.fsf@xenomai.org> <34573B47-B373-46DB-A49D-FB6298AA65DC@gmail.com> <871rd947az.fsf@xenomai.org> <652D6B1D-CE11-4C5B-93E5-0D02B07ABC35@gmail.com> From: Philippe Gerum Subject: Re: [I-PIPE][ARM64] Experimenting on Jetson Xavier In-reply-to: <652D6B1D-CE11-4C5B-93E5-0D02B07ABC35@gmail.com> Date: Mon, 22 Feb 2021 09:39:16 +0100 Message-ID: <87y2fg339n.fsf@xenomai.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable List-Id: Discussions about the Xenomai project List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Deniz =?utf-8?Q?U=C4=9Fur?= Cc: Xenomai Deniz U=C4=9Fur writes: > Hi again, > > So I=E2=80=99ve installed the evl/v5.10 on Jetson Xavier and after settin= g the scaling_governor to performance I got somewhat good results. > > I=E2=80=99ve set the isolcpus=3D0 command line argument but latmus report= s that CPU0 is not isolated. I=E2=80=99m not sure if that=E2=80=99s a bug o= r I=E2=80=99ve missed something. > You cannot isolate CPU0, this is a reserved one Linux-wise. > Other than that I=E2=80=99m getting latencies between +-10us and worst la= tency > is 73us. You may want to run "evl check" for a quick verification of the running kernel configuration wrt real-time. This reads /proc/config.gz on the current system by default unless you pass it a .config file, so CONFIG_IKCONFIG_PROC should be enabled if you want to check a running kernel. > Even though I=E2=80=99ve ran latmus -t I=E2=80=99m still getting negative= latencies. Isn=E2=80=99t that supposed to fix that? > Yep, it should. This can happen with high performance platforms as the tuner is fairly conservative when determining the typical jitter. What is the smallest negative value you get? > evl test reports OK for everything except for scheduler-quota-accuracy an= d sched-tp-accuracy (no kernel support) > You will need CONFIG_EVL_SCHED_QUOTA and CONFIG_EVL_SCHED_TP enabled in your Kconfig to run these tests. The exhaustive list of the core options can be found at https://evlproject.org/core/build-steps/#core-kconfig. > Are these latencies best I can get or are there anything else I can do to= lower/stabilize the latencies? > Isolating the test CPU will certainly help. Next, a closer look to the impact of CPU idling may help, such as measuring the latency with and without idle=3Dpoll on the kernel boot line. As I hinted at earlier, evl check would detect the kernel options which are known to increase the latency figures. There might be more SoC-specific tweaks, I don't know the Jetson enough to figure this out at the moment though. --=20 Philippe.