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 BB0A4C433E0 for ; Thu, 6 Aug 2020 18:58:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0034B20855 for ; Thu, 6 Aug 2020 18:58:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="o6aefiq8"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="ExvAX/Uj" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729027AbgHFS6c (ORCPT ); Thu, 6 Aug 2020 14:58:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35056 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725272AbgHFS6b (ORCPT ); Thu, 6 Aug 2020 14:58:31 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 475E5C061574 for ; Thu, 6 Aug 2020 11:58:31 -0700 (PDT) From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596740309; 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=Eq5i7/DrPIRMT4jncK281CDEQ+oCIA5XaA6tD+TJQss=; b=o6aefiq84HrrzcnIFcl9KjHhfvAUfOhORytwU+6oU9pMiAndAiryDPOnotC+4xslC4wlSP aNKG5/isaQd941YnZKMCHPbRUBTYjWuqFjxcSYQHQ4Ay8yEMikJj6qCJG9bm9z+yfyfG6+ aES/ohalCTTz3/L3Vr8ZBB+97ghv8XCa2WikKNiNG0k2qelcix1SovEgPxbu5DA8u5kk8j wbN585by6dy7UWCVhEG+CWeWwA87y3pItoYjprWrhs2lEr6UPOY+iGFLG+CaITuQBLY8Q9 Ws9tJEXcpzlRfR9SxAhwpELzrEy/ZHqOEKDhwmZe+qbJ7+aK2zxLNTkgj15tFw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596740309; 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=Eq5i7/DrPIRMT4jncK281CDEQ+oCIA5XaA6tD+TJQss=; b=ExvAX/UjbAXVzKraaL9FKnQ5AuwydIzTPeXuFvEvrQfRzXRZKO+YBJk1SU6WIHzE843oUW Nj/Q+wgZClZhDtAg== To: peterz@infradead.org Cc: Valentin Schneider , 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: <20200806114545.GA2674@hirez.programming.kicks-ass.net> References: <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> <874kpgi025.fsf@nanos.tec.linutronix.de> <20200806114545.GA2674@hirez.programming.kicks-ass.net> Date: Thu, 06 Aug 2020 20:58:26 +0200 Message-ID: <87mu37ha99.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 Peter, peterz@infradead.org writes: > On Thu, Aug 06, 2020 at 11:41:06AM +0200, Thomas Gleixner wrote: >> 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. > > The safety thing is concerned with RT tasks. It doesn't pretend to help > with runnaway IRQs, never has, never will. Of course not. But without irq accounting the runtime is accounted on the runaway task which causes it to throttle. > The further extreme is an interrupt storm, those have always taken a > machine down. If every interrupt is actually handled, then yes. > Accounting unrelated IRQ time to RT tasks is equally wrong, the task > execution is unrelated to the IRQs. The config option at least offers > insight into where time goes -- and it's a config option because doing > time accounting on interrupts adds overhead :/ Right, but it's not totally out of the world either to make the throttler do: if (rt_runtime + irq_time > threshold) try_to_keep_the_box_alive() > This really is a no-win all round. That's not the question here :) > The only 'sensible' option here is threaded IRQs, where the IRQ line > gets disabled until the handler thread has ran, that also helps with IRQ > storms. I'm not against enforcing threaded IRQs. :) Thanks, tglx 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=-4.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,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 7E7A3C433E0 for ; Thu, 6 Aug 2020 18:59:58 +0000 (UTC) Received: from merlin.infradead.org (merlin.infradead.org [205.233.59.134]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AA0DE20855 for ; Thu, 6 Aug 2020 18:59:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="lX/CxUAZ"; 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b=lX/CxUAZ/q8njUKr2D9S54TRA ROvO3V9yjcbmg7TQQp8wxTAwVtONoraxRroxa3lVE3BYNdYgH6vXwn66+l6Nmir662/sxf1IEuOCC aADSsagWq914juawpRTW69X2mqaXxx9y/dQur54a7vknYFD8UYRS6ju6vWYmHCpRH5fqgcq2iMpJ5 LdtskyzKUBC83SRqPqnKKSyxKtIvgCNaHURaQMzoJnkdsS6xlD+9ZPy16mP5o1OjutEEVm8JSoWB+ cO3Cz81qzGbqNYWnY67r9KYnJ4FhArJCyBULAP3buRPfXgfMiMYiHHN0xFaUwbjFVl0WbVCz5JbR4 EGebGq+Iw==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k3l63-0006KL-Ce; Thu, 06 Aug 2020 18:58:35 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by merlin.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1k3l60-0006JL-HF for linux-arm-kernel@lists.infradead.org; Thu, 06 Aug 2020 18:58:33 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596740309; 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=Eq5i7/DrPIRMT4jncK281CDEQ+oCIA5XaA6tD+TJQss=; b=o6aefiq84HrrzcnIFcl9KjHhfvAUfOhORytwU+6oU9pMiAndAiryDPOnotC+4xslC4wlSP aNKG5/isaQd941YnZKMCHPbRUBTYjWuqFjxcSYQHQ4Ay8yEMikJj6qCJG9bm9z+yfyfG6+ aES/ohalCTTz3/L3Vr8ZBB+97ghv8XCa2WikKNiNG0k2qelcix1SovEgPxbu5DA8u5kk8j wbN585by6dy7UWCVhEG+CWeWwA87y3pItoYjprWrhs2lEr6UPOY+iGFLG+CaITuQBLY8Q9 Ws9tJEXcpzlRfR9SxAhwpELzrEy/ZHqOEKDhwmZe+qbJ7+aK2zxLNTkgj15tFw== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596740309; 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=Eq5i7/DrPIRMT4jncK281CDEQ+oCIA5XaA6tD+TJQss=; b=ExvAX/UjbAXVzKraaL9FKnQ5AuwydIzTPeXuFvEvrQfRzXRZKO+YBJk1SU6WIHzE843oUW Nj/Q+wgZClZhDtAg== To: peterz@infradead.org Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting In-Reply-To: <20200806114545.GA2674@hirez.programming.kicks-ass.net> References: <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> <874kpgi025.fsf@nanos.tec.linutronix.de> <20200806114545.GA2674@hirez.programming.kicks-ass.net> Date: Thu, 06 Aug 2020 20:58:26 +0200 Message-ID: <87mu37ha99.fsf@nanos.tec.linutronix.de> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200806_145832_681777_44D1F2B2 X-CRM114-Status: GOOD ( 11.92 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mw@semihalf.com, paulmck@kernel.org, Anna-Maria Gleixner , catalin.marinas@arm.com, Alison Wang , linux-kernel@vger.kernel.org, leoyang.li@nxp.com, vladimir.oltean@nxp.com, Kurt Kanzenbach , Vladimir Oltean , will@kernel.org, Valentin Schneider , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Peter, peterz@infradead.org writes: > On Thu, Aug 06, 2020 at 11:41:06AM +0200, Thomas Gleixner wrote: >> 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. > > The safety thing is concerned with RT tasks. It doesn't pretend to help > with runnaway IRQs, never has, never will. Of course not. But without irq accounting the runtime is accounted on the runaway task which causes it to throttle. > The further extreme is an interrupt storm, those have always taken a > machine down. If every interrupt is actually handled, then yes. > Accounting unrelated IRQ time to RT tasks is equally wrong, the task > execution is unrelated to the IRQs. The config option at least offers > insight into where time goes -- and it's a config option because doing > time accounting on interrupts adds overhead :/ Right, but it's not totally out of the world either to make the throttler do: if (rt_runtime + irq_time > threshold) try_to_keep_the_box_alive() > This really is a no-win all round. That's not the question here :) > The only 'sensible' option here is threaded IRQs, where the IRQ line > gets disabled until the handler thread has ran, that also helps with IRQ > storms. I'm not against enforcing threaded IRQs. :) Thanks, tglx _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel