From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 66656C47274 for ; Thu, 6 Aug 2020 11:13:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 988F522D02 for ; Thu, 6 Aug 2020 11:13:31 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="0en1W3fo"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="4eBnpOGf" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729222AbgHFJlh (ORCPT ); Thu, 6 Aug 2020 05:41:37 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:57040 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726094AbgHFJlJ (ORCPT ); Thu, 6 Aug 2020 05:41:09 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596706866; 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=7h1NwChE7k/KZnYmQuWPK12OfyVN6+DmIy8syMh+/Ks=; b=0en1W3foTyJQ/a3ORD69xVDuy6RGBmSpumUZOiO+zNNjdZ98YVdw025EVEVh0vFD7aYK5L I7/sw6SwqJ06boKGugm4ApL7T7jZi+K3MSw9qlCNmFfu9EErsq8zZIiorKQ3pqjJO/xSAH dXWv/P+S53NyOmxXmnn1hUvYJr7J6VS8rDiEaRTxqjuOzhYYRsVWfUQwB6kW+jys94AT4a HEswFNxvCS+6lkzecrs4K1zQ+a1c6eK50+ACvB9c97Pt0WIT9KYaegmfP1iAwrvUpKUUKx cr6Twjjgi6OcvnBtrgXF9m3y8Ei6KtDwlkecdJqbBsOGPUVfBIIARWxzghzVxQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596706866; 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=7h1NwChE7k/KZnYmQuWPK12OfyVN6+DmIy8syMh+/Ks=; b=4eBnpOGf08nGpnL+jnNqH5dmgNbgf5eT0rVBjjVBHEiNG3JQgMsYvX+22Ccpdz12hJBVUZ WJupblTyigLCvCCw== To: peterz@infradead.org, Valentin Schneider Cc: Vladimir Oltean , Kurt Kanzenbach , Alison Wang , catalin.marinas@arm.com, will@kernel.org, paulmck@kernel.org, mw@semihalf.com, leoyang.li@nxp.com, vladimir.oltean@nxp.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Anna-Maria Gleixner Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting In-Reply-To: <20200805153120.GU2674@hirez.programming.kicks-ass.net> References: <87mu3ho48v.fsf@kurt> <20200730082228.r24zgdeiofvwxijm@skbuf> <873654m9zi.fsf@kurt> <87lfiwm2bj.fsf@nanos.tec.linutronix.de> <20200803114112.mrcuupz4ir5uqlp6@skbuf> <87d047n4oh.fsf@nanos.tec.linutronix.de> <875z9zmt4i.fsf@nanos.tec.linutronix.de> <20200805134002.GQ2674@hirez.programming.kicks-ass.net> <20200805153120.GU2674@hirez.programming.kicks-ass.net> Date: Thu, 06 Aug 2020 11:41:06 +0200 Message-ID: <874kpgi025.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org peterz@infradead.org writes: > On Wed, Aug 05, 2020 at 02:56:49PM +0100, Valentin Schneider wrote: > >> I've been tempted to say the test case is a bit bogus, but am not familiar >> enough with the RT throttling details to stand that ground. That said, from >> both looking at the execution and the stress-ng source code, it seems to >> unconditionally spawn 32 FIFO-50 tasks (there's even an option to make >> these FIFO-99!!!), which is quite a crowd on monoCPU systems. > > Oh, so it's a case of: we do stupid without tuning and the system falls > over. I can live with that. It's not a question of whether you can live with that behaviour for a particular silly test case. The same happens with a single RT runaway task with enough interrupt load on a UP machine. Just validated that. And that has nothing to do with a silly test case. Sporadic runaways due to a bug in a once per week code path simply can happen and having the safety net working depending on a config option selected or not is just wrong. Thanks, tglx