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 5ADE2C3A5A1 for ; Wed, 28 Aug 2019 14:07:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 32F9E2189D for ; Wed, 28 Aug 2019 14:07:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726603AbfH1OH6 (ORCPT ); Wed, 28 Aug 2019 10:07:58 -0400 Received: from Galois.linutronix.de ([193.142.43.55]:47429 "EHLO Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726410AbfH1OH6 (ORCPT ); Wed, 28 Aug 2019 10:07:58 -0400 Received: from [5.158.153.52] (helo=nanos.tec.linutronix.de) by Galois.linutronix.de with esmtpsa (TLS1.2:DHE_RSA_AES_256_CBC_SHA256:256) (Exim 4.80) (envelope-from ) id 1i2ybc-0005Vf-Ga; Wed, 28 Aug 2019 16:07:24 +0200 Date: Wed, 28 Aug 2019 16:07:19 +0200 (CEST) From: Thomas Gleixner To: Ming Lei cc: LKML , 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, Daniel Lezcano Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism In-Reply-To: <20190828135054.GA23861@ming.t460p> Message-ID: References: <20190827085344.30799-1-ming.lei@redhat.com> <20190827085344.30799-2-ming.lei@redhat.com> <20190827225827.GA5263@ming.t460p> <20190828110633.GC15524@ming.t460p> <20190828135054.GA23861@ming.t460p> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On Wed, 28 Aug 2019, Ming Lei wrote: > On Wed, Aug 28, 2019 at 01:23:06PM +0200, Thomas Gleixner wrote: > > On Wed, 28 Aug 2019, Ming Lei wrote: > > > On Wed, Aug 28, 2019 at 01:09:44AM +0200, Thomas Gleixner wrote: > > > > > > Also how is that supposed to work when sched_clock is jiffies based? > > > > > > > > > > Good catch, looks ktime_get_ns() is needed. > > > > > > > > And what is ktime_get_ns() returning when the only available clocksource is > > > > jiffies? > > > > > > IMO, it isn't one issue. If the only clocksource is jiffies, we needn't to > > > expect high IO performance. Then it is fine to always handle the irq in > > > interrupt context or thread context. > > > > > > However, if it can be recognized runtime, irq_flood_detected() can > > > always return true or false. > > > > Right. The clocksource is determined at runtime. And if there is no high > > resolution clocksource then that function will return crap. > > This patch still works even though the only clocksource is jiffies. Works by some definition of works, right? > > Well, yes. But it's trivial enough to utilize parts of it for your > > purposes. > > >From the code of kernel/irq/timing.c: > > 1) record_irq_time() only records the start time of one irq, and not > consider the time taken in interrupt handler, so we can't figure out > the real interval between two do_IRQ() on one CPU I said utilize and that means that the infrastructure can be used and extended. I did not say that it solves your problem, right? > 2) irq/timing doesn't cover softirq That's solvable, right? > Daniel, could you take a look and see if irq flood detection can be > implemented easily by irq/timing.c? I assume you can take a look as well, right? Thanks, tglx