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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 C4F30C3A5A3 for ; Tue, 27 Aug 2019 14:42:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9C79B206E0 for ; Tue, 27 Aug 2019 14:42:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730030AbfH0Oml (ORCPT ); Tue, 27 Aug 2019 10:42:41 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:43993 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726170AbfH0Omk (ORCPT ); Tue, 27 Aug 2019 10:42:40 -0400 Received: from p5de0b6c5.dip0.t-ipconnect.de ([93.224.182.197] helo=nanos) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1i2cfc-0000BW-0E; Tue, 27 Aug 2019 16:42:04 +0200 Date: Tue, 27 Aug 2019 16:42:02 +0200 (CEST) From: Thomas Gleixner To: Ming Lei cc: linux-kernel@vger.kernel.org, Long Li , Ingo Molnar , Peter Zijlstra , Keith Busch , Jens Axboe , Christoph Hellwig , Sagi Grimberg , John Garry , Hannes Reinecke , linux-nvme@lists.infradead.org, linux-scsi@vger.kernel.org Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism In-Reply-To: <20190827085344.30799-2-ming.lei@redhat.com> Message-ID: References: <20190827085344.30799-1-ming.lei@redhat.com> <20190827085344.30799-2-ming.lei@redhat.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Linutronix-Spam-Score: -1.0 X-Linutronix-Spam-Level: - X-Linutronix-Spam-Status: No , -1.0 points, 5.0 required, ALL_TRUSTED=-1,SHORTCIRCUIT=-0.0001 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 27 Aug 2019, Ming Lei wrote: > +/* > + * Update average irq interval with the Exponential Weighted Moving > + * Average(EWMA) > + */ > +static void irq_update_interval(void) > +{ > +#define IRQ_INTERVAL_EWMA_WEIGHT 128 > +#define IRQ_INTERVAL_EWMA_PREV_FACTOR 127 > +#define IRQ_INTERVAL_EWMA_CURR_FACTOR (IRQ_INTERVAL_EWMA_WEIGHT - \ > + IRQ_INTERVAL_EWMA_PREV_FACTOR) Please do not stick defines into a function body. That's horrible. > + > + int cpu = raw_smp_processor_id(); > + struct irq_interval *inter = per_cpu_ptr(&avg_irq_interval, cpu); > + u64 delta = sched_clock_cpu(cpu) - inter->last_irq_end; Why are you doing that raw_smp_processor_id() dance? The call site has interrupts and preemption disabled. Also how is that supposed to work when sched_clock is jiffies based? > + inter->avg = (inter->avg * IRQ_INTERVAL_EWMA_PREV_FACTOR + > + delta * IRQ_INTERVAL_EWMA_CURR_FACTOR) / > + IRQ_INTERVAL_EWMA_WEIGHT; We definitely are not going to have a 64bit multiplication and division on every interrupt. Asided of that this breaks 32bit builds all over the place. Thanks, tglx