From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from relay6-d.mail.gandi.net (relay6-d.mail.gandi.net [217.70.183.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6466158E2A5 for ; Thu, 15 Oct 2026 18:20:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.183.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792088428; cv=none; b=htD6VHQcjFhfS7f4eB+Mb7qgOITKqKTWKy8AglxqlAni4IA4YLD59iM3A13MeLhFezjcMHhc9SFP12R+O+3+qoxa1cZbuSMNdBornbpYyvDcfWicCaO2MZ8DpMojg7vEFjool2TWsCaYU7aoIttdVndNBYmbZIV2vYy4E5lIlGM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1792088428; c=relaxed/simple; bh=Bp7J97Q6ZpOcN+4KCLTmqwitDOxQdHwepMj5VBrdsEs=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=B7z5rCGo1zcbzOlArLOcWkWGMS0vJ7l9fnuQKlDSVr8S7T2Js9jf4bH86d2pynAT1IFAroD09eCXK4j8eaRc2anKuwtS5uT+XdZLLB2BndlS1N+sqNbaNTyQoqYkXYPu6lkGuTgQ7NMdcj8Gf9+Fa0MjiLic8N5WLphPLBhgB20= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org; spf=pass smtp.mailfrom=xenomai.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b=X/I2gvuH; arc=none smtp.client-ip=217.70.183.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=xenomai.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=xenomai.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=xenomai.org header.i=@xenomai.org header.b="X/I2gvuH" Received: by mail.gandi.net (Postfix) with ESMTPSA id 164053ED7E; Thu, 15 Oct 2026 18:20:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=xenomai.org; s=gm1; t=1792088413; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=Wsn5FHDZTF+J6AGXyo6agF6VLIh81Z4ZXWtQBDQ+pPY=; b=X/I2gvuHOoyXiRQCeTiAtT9v19GOfZDbh9JwjYWpwMtmIWyz79tAdGP03lqMT8L10S2dUi AfLnpyS/7BBOdjsPegjU1Y9GVo2BpxxJJh7xAsT2CE1/Kdgjo1WOTFCN1pEs9zOmuWGAYv Q/KHirf2SzW04zRkOywqYvr1J+aoMsIYXtlFYpFlpKI2Zpg9s0ixENbNwPdlvfvV8LPriq tL9jw/c0dfj6aMKd8fL2XY17hSMnP8pg5P6305QRslPu8XigGGxqlrpKJVyhe7mnajiumh Un8GOM1VUDsuKn6w4dYO4fHcem8mL89OnBKesZpHosyyjwnbJqZhbspG/qAxpA== From: Philippe Gerum To: "Richard Weinberger" Cc: "Jan Kiszka" , "Richard Weinberger" , "Xenomai" , "Florian Bezdeka" , "guangfeng.wang" Subject: Re: AW: Call today In-Reply-To: (Richard Weinberger's message of "Thu, 15 Oct 2026 11:57:55 +0000") References: <98caad22-455d-41ca-bfaa-f32289c7c8e8@siemens.com> <9f598cf9-5a8e-4f3e-84ae-5e1ca7bb66de@siemens.com> User-Agent: mu4e 1.12.12; emacs 30.2 Date: Thu, 15 Oct 2026 20:20:12 +0200 Message-ID: <87ik32ltb7.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 X-GND-Sasl: rpm@xenomai.org X-GND-State: clean X-GND-Score: -100 X-GND-Cause: 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 "Richard Weinberger" writes: > Am Wed, Oct 14, 2026, 11:51 schrieb Jan Kiszka : >> > I was about to ask whether somebody has (long term) latency plots >> > for i.MX8M mini SoCs. >> > >> >> We do not have one in CI lab, but Philippe has/had one in scope for >> Xenomai 4 and may have related numbers from his lab. > > Would be good to have some solid numbers. > On my i.mx8mm board I see latencies around 45us. > What worries me a bit, copying memory on a different CPU in > a Linux task significantly increases the latency up to 100us. > My experience with the Variscite Dart i.MX8M Mini back in 2020 has not been that nice either. Structural latencies observed were > 200 us with a 10Khz loop, on any attempt with every rt option: x3, x4, preempt-rt, all the same. I was using the Variscite kernel fork of the NXP kernel fork... Way too many forks on this table, so I cannot tell whether some gremlin was hiding in the bsp layer which would have explained this. That was roughly enough to sustain real-time audio requirements at that time, but certainly not good enough for stricter requirements. This said, those measurements date back to 2020 (kernel 4.19.35), so things might have evolved since then, take my word with a grain of salt when it comes to the current status of this series. Last year, I ran evl on a Phytec i.MX8M "Pollux" board. Much better figures (read: something we can use), but running evl for a short time only on this board was purely opportunistic, because this target was not aimed at real-time work and left my desk early. PS: The issue you mentioned about seeing weird figures when memory traffic happens between different CPUs rings a bell. Back in 2022, I did some measurements on a TI am625 SoC, observing high impact on an isolated CPU running the latency test, caused by tasks running on other CPUs, moving memory around and switching context at high rate, to the point where using this platform for real-time duty was a non-starter. A peculiarity which must have had a reasonable explanation is that the busier the CPU core running the sampling loop, the (really, really) better the results. I sent some questions to TI about the whole issue at that time, a TI engineer answered that the problem was under investigation, then the discussion stalled, and I did not get back to it. Again, this is old news, so the situation may have improved (hopefully). -- Philippe.