From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 04C371A0728 for ; Fri, 5 Sep 2025 14:03:14 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757080999; cv=none; b=J85nPGf6VnWpjdxiZ6Vw1SoBcsHMItHXE4AFJEu4bYzzfUcinpf64RMyDZnh8hZQUh3BNTO2KyM+B3Um7D8eV7gppS8wepWQCXE1XHin9snjTR79BhwLlIsAk30FAPyYy27vDw5wFyr20Xv07T/1VJAr5lZuYGaeg++Y79I+oXI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757080999; c=relaxed/simple; bh=wO2ewgLw1pAmzKTO66fNA+QZsZ4gNQmcpk2APGSqLj8=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=j4qU6IPNv66aya1sKMT23jSns+lT+oCdsaxGEGVwptYITCyfsZbGTp9QB9MQCmWBW69z6l97J8f2fIe5BZ2F7ABRxGnkRPcA8nGntqdKp39Oy/zWungjT0/WJCxBkXMApHE700aiz288ErFHyyajZ+F0qYBqfV8+BXxgEzygXl0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=lxMa0Y3i; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=NfgPnJ3k; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="lxMa0Y3i"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="NfgPnJ3k" From: John Ogness DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1757080992; 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=wO2ewgLw1pAmzKTO66fNA+QZsZ4gNQmcpk2APGSqLj8=; b=lxMa0Y3i+nN+fDtqARQjoZplk+Slidu44rr8FcKUuZWeRlJqr1vLMkHyoG2YlkfuVARu2T rQ5TMoL2EvOIL4VWkFQ6n0gfW4w71aLJ3CxfVAtw5q2L52Jo1DrmtPDo6gO/krSHmjuxSD HpTBC2/XiNRXsLdkqsCYrEO+MULjeZt3Y4w4aT0Y+6WqiSJCpq9idMmcASP9RoXB9S7Dcs TX9EFIu/sPVdsPeodgzeUZF05otxxel0YdpWe8gMM5MQbaFCxHcgprp72O6BDwwSlPzOj9 89WJa6vlwCeKKeTg0Xs1IFD8xwVwaaxaTpFI/j68bpu/B5Y17vj34cdOntWjEw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1757080992; 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=wO2ewgLw1pAmzKTO66fNA+QZsZ4gNQmcpk2APGSqLj8=; b=NfgPnJ3kyaflHCDWh+3NDrztOipsgITdTtdrxtyloaml5seRW2nrDNSer2cdYU6haftfFL IrN3w+ThDkmriyBA== To: Marc Gonzalez , Daniel Wagner Cc: linux-rt-users@vger.kernel.org, Steven Rostedt , Thomas Gleixner , Sebastian Andrzej Siewior , Daniel Wagner , Clark Williams , Pavel Machek , Luis Goncalves , John McCalpin Subject: Re: Large(ish) variance induced by SCHED_FIFO In-Reply-To: References: <5f7496eb-bf62-4cc9-bef0-9cae97a93dca@free.fr> Date: Fri, 05 Sep 2025 16:09:12 +0206 Message-ID: <841polf13z.fsf@jogness.linutronix.de> Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On 2025-09-05, Marc Gonzalez wrote: > (I used CLOCK_MONOTONIC_RAW.) Not really relevant to your issue, but you should always use CLOCK_MONOTONIC. > It looks like there is some kind of 50 millisecond quantum > involved somewhere somehow. Did you forget to disable RT throttling? $ sudo sysctl -w kernel.sched_rt_runtime_us=-1 If you check the kernel logs, you would see a message about throttling: "sched: RT throttling activated" John Ogness