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 60AEBC433E0 for ; Thu, 6 Aug 2020 19:03:29 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9529D206C3 for ; Thu, 6 Aug 2020 19:03:29 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="U7gIsbri"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Sads8gc+" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729891AbgHFTD2 (ORCPT ); Thu, 6 Aug 2020 15:03:28 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:59622 "EHLO galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728346AbgHFTD0 (ORCPT ); Thu, 6 Aug 2020 15:03:26 -0400 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596740604; 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=VB5BucQx5bpvgXTjit7Tp0UjVe4bVgUOv+xvLbLyxrU=; b=U7gIsbriuFfDgYrSTfYmSEZxoXdCZO49gi9xVPbIJ4f/gxXyJSm/+FuFAuNe0IkJk4WX3e WH3NkPlXmihhh7Ln8CQ22mIbw2xl8/tYEoZJZnr+Jj4G7OTbohd+L1sLHY2gR5CX836Pr4 pLS9t4qnhTAtPVoyD9ApWPv/oWqAJHJLkHkkry2cEsfFTU6TdL3/ohvEishyH1MIsiSyCV GfH1IjS+pmdKRg43a44I1NCfEgKzSCf1wQytanduVnf4RGf7TcaNLLIXCCEASpXvKEIuve jMfLbU1yNHSBzGsrBHfWQfM80zJ41QZJuSWcEQVRxDwXO9s0JNQN2v0LKG9Osg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596740604; 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=VB5BucQx5bpvgXTjit7Tp0UjVe4bVgUOv+xvLbLyxrU=; b=Sads8gc+ZuOg1bshtFmy5iMjP2tqRRHMZgt6TZnKHEZnCAr3UtFrwwQAUVC+WsM0fiBzdQ G3hhFGBb+CBBVWCQ== To: paulmck@kernel.org, peterz@infradead.org Cc: Valentin Schneider , Vladimir Oltean , Kurt Kanzenbach , Alison Wang , catalin.marinas@arm.com, will@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: <20200806132710.GL4295@paulmck-ThinkPad-P72> References: <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> <20200806132710.GL4295@paulmck-ThinkPad-P72> Date: Thu, 06 Aug 2020 21:03:24 +0200 Message-ID: <87k0ybha0z.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 Paul, "Paul E. McKenney" writes: > On Thu, Aug 06, 2020 at 01:45:45PM +0200, peterz@infradead.org wrote: >> The safety thing is concerned with RT tasks. It doesn't pretend to help >> with runnaway IRQs, never has, never will. > > Getting into the time machine back to the 1990s... > > DYNIX/ptx had a discretionary mechanism to deal with excessive interrupts. > There was a function that long-running interrupt handlers were supposed > to call periodically that would return false if the system felt that > the CPU had done enough interrupts for the time being. In that case, > the interrupt handler was supposed to schedule itself for a later time, > but leave the interrupt unacknowledged in order to prevent retriggering > in the meantime. > > Of course, this mechanism would be rather less helpful in Linux. > > For one, Linux has way more device drivers and way more oddball devices. > In contrast, the few devices that DYNIX/ptx supported were carefully > selected, and the selection criteria included being able to put up > with this sort of thing. Also, the fact that there was but a handful > of device drivers meant that changes like this could be more easily > propagated through all drivers. We could do that completely at the core interrupt handling level. > Also, Linux supports way more workloads. In contrast, DYNIX/ptx could > pick a small percentage of each CPU that would be permitted to be used > by hardware interrupt handlers. As in there are probably Linux workloads > that run >90% of some poor CPU within hardware interrupt handlers. Yet another tunable. /me runs 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 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 9483BC433E0 for ; Thu, 6 Aug 2020 19:05:08 +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 BC0ED206C3 for ; Thu, 6 Aug 2020 19:05:08 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Esqq02iV"; dkim=fail reason="signature verification failed" (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="U7gIsbri"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="Sads8gc+" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org BC0ED206C3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linutronix.de Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=merlin.20170209; h=Sender:Content-Transfer-Encoding: Content-Type:Cc:List-Subscribe:List-Help:List-Post:List-Archive: List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:References:In-Reply-To: Subject:To:From:Reply-To:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=Ce25aAQGORHLf7lqtEl+kp3plh5bdmBPhjXmaTJ4B94=; b=Esqq02iV+R5Pst4Hamweu1LQ0 QPR0Q6YL4KAqhFQeShHdXZr7SN7o/3u8VVXVflgthqMWRTd3Wpv0iD7vgHdoNa306MXNf9TQdHyN5 j5aHsE2y1J1G42E3kiT0gg9Awz6xWXboCL46PeLUg0jKVH2lM+7NRXDKF5qOlA/9MYWL0gH2d3miy G/j0ObXNZyJMuv1RyrCSQG1gcDEiwzgiod82gAiPTnPHRGDnxE2pHPpDZWkSdRaM3cX59hKrwG2FJ oDKlD/rTiBxfOLkEjndJjsKGSw3fVJ0+XX7dwexwNHpxzWS1l0PwilF1pTbE/3sl6xg/UKxJsZjTd bXjQKZXHQ==; Received: from localhost ([::1] helo=merlin.infradead.org) by merlin.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1k3lAn-00071S-Qb; Thu, 06 Aug 2020 19:03:29 +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 1k3lAk-00070X-7w for linux-arm-kernel@lists.infradead.org; Thu, 06 Aug 2020 19:03:27 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1596740604; 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=VB5BucQx5bpvgXTjit7Tp0UjVe4bVgUOv+xvLbLyxrU=; b=U7gIsbriuFfDgYrSTfYmSEZxoXdCZO49gi9xVPbIJ4f/gxXyJSm/+FuFAuNe0IkJk4WX3e WH3NkPlXmihhh7Ln8CQ22mIbw2xl8/tYEoZJZnr+Jj4G7OTbohd+L1sLHY2gR5CX836Pr4 pLS9t4qnhTAtPVoyD9ApWPv/oWqAJHJLkHkkry2cEsfFTU6TdL3/ohvEishyH1MIsiSyCV GfH1IjS+pmdKRg43a44I1NCfEgKzSCf1wQytanduVnf4RGf7TcaNLLIXCCEASpXvKEIuve jMfLbU1yNHSBzGsrBHfWQfM80zJ41QZJuSWcEQVRxDwXO9s0JNQN2v0LKG9Osg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1596740604; 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=VB5BucQx5bpvgXTjit7Tp0UjVe4bVgUOv+xvLbLyxrU=; b=Sads8gc+ZuOg1bshtFmy5iMjP2tqRRHMZgt6TZnKHEZnCAr3UtFrwwQAUVC+WsM0fiBzdQ G3hhFGBb+CBBVWCQ== To: paulmck@kernel.org, peterz@infradead.org Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting In-Reply-To: <20200806132710.GL4295@paulmck-ThinkPad-P72> References: <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> <20200806132710.GL4295@paulmck-ThinkPad-P72> Date: Thu, 06 Aug 2020 21:03:24 +0200 Message-ID: <87k0ybha0z.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_150326_436213_195A7BC5 X-CRM114-Status: GOOD ( 14.75 ) 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, 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 Paul, "Paul E. McKenney" writes: > On Thu, Aug 06, 2020 at 01:45:45PM +0200, peterz@infradead.org wrote: >> The safety thing is concerned with RT tasks. It doesn't pretend to help >> with runnaway IRQs, never has, never will. > > Getting into the time machine back to the 1990s... > > DYNIX/ptx had a discretionary mechanism to deal with excessive interrupts. > There was a function that long-running interrupt handlers were supposed > to call periodically that would return false if the system felt that > the CPU had done enough interrupts for the time being. In that case, > the interrupt handler was supposed to schedule itself for a later time, > but leave the interrupt unacknowledged in order to prevent retriggering > in the meantime. > > Of course, this mechanism would be rather less helpful in Linux. > > For one, Linux has way more device drivers and way more oddball devices. > In contrast, the few devices that DYNIX/ptx supported were carefully > selected, and the selection criteria included being able to put up > with this sort of thing. Also, the fact that there was but a handful > of device drivers meant that changes like this could be more easily > propagated through all drivers. We could do that completely at the core interrupt handling level. > Also, Linux supports way more workloads. In contrast, DYNIX/ptx could > pick a small percentage of each CPU that would be permitted to be used > by hardware interrupt handlers. As in there are probably Linux workloads > that run >90% of some poor CPU within hardware interrupt handlers. Yet another tunable. /me runs _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel