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 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 AE4B3C433DF for ; Mon, 3 Aug 2020 19:22:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1F92B22BF3 for ; Mon, 3 Aug 2020 19:22:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="rUzpeCBE"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="leD5YLtY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727923AbgHCTW4 (ORCPT ); Mon, 3 Aug 2020 15:22:56 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:39072 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726615AbgHCTW4 (ORCPT ); Mon, 3 Aug 2020 15:22:56 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596482574; 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=fnh19shj45XwVSRJ/AsU92QxNDDk6Jg7+Bn6+Y9OBbc=; b=rUzpeCBEfAgw3bwmckKW5o5Lg46V6f6rMapfuMyZ3rikpOPw5fC9DLXpAoas5c1yYEm5oD 3KxxuE24rejUH8jFJ+SvhJ2m6ervnaNyfxbXM7tJubxjNzBjG0s0JjXKZ/KPZGT7s2Yfxj AEzac5sJua/pFnjUH/pP8u6hGrgB5Z5c9gIMp5xtVbV8ztGNGDQkOQ+M54m8pdUpvq6kOy oXkaoCGuRPsd3QGCX9v6ThiXXvy9PIwZwrNRo8LAlmuSnyr8aHZEwbVKw5MH2NeIMfxIps NokiXzj0njkNosO6DU3BBpR+L0cPCKCWvhHE9xi55YfiIg9r45Ry0FBGfGzGYQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596482574; 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=fnh19shj45XwVSRJ/AsU92QxNDDk6Jg7+Bn6+Y9OBbc=; b=leD5YLtY+Wa4TNm5tSNxVe1HLJg5bjMMOIlBeWeaR5cABf1s2j5aO6i4agBKOqWNhw/0F/ uErwH/5+UXd98XCw== To: 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 , Peter Zijlstra Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting In-Reply-To: References: <20200729033934.22349-1-alison.wang@nxp.com> <877dumbtoi.fsf@kurt> <20200729094943.lsmhsqlnl7rlnl6f@skbuf> <87mu3ho48v.fsf@kurt> <20200730082228.r24zgdeiofvwxijm@skbuf> <873654m9zi.fsf@kurt> <87lfiwm2bj.fsf@nanos.tec.linutronix.de> <20200803114112.mrcuupz4ir5uqlp6@skbuf> <87d047n4oh.fsf@nanos.tec.linutronix.de> Date: Mon, 03 Aug 2020 21:22:53 +0200 Message-ID: <875z9zmt4i.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 Valentin, Valentin Schneider writes: > On 03/08/20 16:13, Thomas Gleixner wrote: >> Vladimir Oltean writes: >>>> 1) When irq accounting is disabled, RT throttling kicks in as >>>> expected. >>>> >>>> 2) With irq accounting the RT throttler does not kick in and the RCU >>>> stall/lockups happen. >>> What is this telling us? >> >> It seems that the fine grained irq time accounting affects the runtime >> accounting in some way which I haven't figured out yet. >> > > With IRQ_TIME_ACCOUNTING, rq_clock_task() will always be incremented by a > lesser-or-equal value than when not having the option; you start with the > same delta_exec but slice some for the IRQ accounting, and leave the rest > for the rq_clock_task() (+paravirt). > > IIUC this means that if you spend e.g. 10% of the time in IRQ and 90% of > the time running the stress-ng RT tasks, despite having RT tasks hogging > the entirety of the "available time" it is still only 90% runtime, which is > below the 95% default and the throttling doesn't happen. totaltime = irqtime + tasktime Ignoring irqtime and pretending that totaltime is what the scheduler can control and deal with is naive at best. Thanks, tglx