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[81.38.137.104]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3cf34494776sm18838418f8f.61.2025.09.02.02.52.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 02 Sep 2025 02:52:00 -0700 (PDT) From: "Jorge Ramirez-Ortiz, Gmail" X-Google-Original-From: "Jorge Ramirez-Ortiz, Gmail" Date: Tue, 2 Sep 2025 11:51:59 +0200 To: Philippe Gerum Cc: Jan Kiszka , Tobias Schaffner , xenomai@lists.linux.dev Subject: Re: [libevl][PATCH 1/4] Copy dohell from Xenomai 3 Message-ID: References: <20240613134557.4013044-1-tobias.schaffner@siemens.com> <20240613134557.4013044-2-tobias.schaffner@siemens.com> <87frtgrker.fsf@xenomai.org> <877cesrfir.fsf@xenomai.org> Precedence: bulk X-Mailing-List: xenomai@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <877cesrfir.fsf@xenomai.org> On 13/06/24 17:55:02, Philippe Gerum wrote: > > Jan Kiszka writes: > > > On 13.06.24 16:23, Philippe Gerum wrote: > >> > >> Tobias Schaffner writes: > >> > >>> Dohell is used as the default load generator in Xenomai 3. Add it to > >>> libevl to be able to stress the system while testing evl. > >>> > >> > >> dohell is obsolete. Let's move to stress-ng or something alike for x4. > >> > > > > See my comment on patch 3: If you can name a configuration of stress-ng > > that stresses a co-kernel more than what dohell does, we can take it. > > Otherwise, I would strongly recommend to not do less hell over here. > > > > The most important stress dohell applies is basically hackbench and a dd > loop trashing the D-cache. The latter can be obtained with a combo of > VM+I/O tests from stress-ng. So basically, the whole issue boils down to > having hackbench on board, provided we cannot generate the same load > profile with stress-ng with a CPU bound stressor. Besides, I never saw > any added value in running ltp tests compared to a combo of stress-ng > stressors when it comes to latency testing. > > We obviously don't want to throw less hell, but throwing more obsolete > stuff is not an option either. So that's a NAK for v4 ATM, I'll gather > more information about how we could leverage stress-ng in order to > compare to dohell. This is worth a shot. I should start by apologizing for not having delivered a proper, stress-ng case study yet. In my defense (if that counts), I got sidetracked by day-to-day work and the long process of getting latmon gpio support merged into Zephyr[1] — which ended up taking > six months of back-and-forth. BTW If you have access to one of these devices [2] (they’re inexpensive), plus a couple of GPIOs on your Xenomai-enabled board and a network interface, they make it quite practical to collect long-term traces in an automated way. So comming back to the discussion, I still believe that the better path is to validate and if necessary extend stress-ng. Just as monitoring tools like latmon dont belong in the Xenomai repository (the Zephyr work above mentioned is a step on that direction), I think stress tools should be kept out as well. IMO this separation of concerns will also help those trying to decide between PREEMPT_RT and Xenomai for their use cases. [1] https://docs.zephyrproject.org/latest/samples/net/latmon/README.html [2] https://docs.zephyrproject.org/latest/boards/nxp/frdm_k64f/doc/index.html