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=-2.3 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 065F1C3A5A2 for ; Tue, 3 Sep 2019 07:29:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D6DD522DBF for ; Tue, 3 Sep 2019 07:29:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727781AbfICH3E (ORCPT ); Tue, 3 Sep 2019 03:29:04 -0400 Received: from mx1.redhat.com ([209.132.183.28]:34676 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725878AbfICH3E (ORCPT ); Tue, 3 Sep 2019 03:29:04 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 1A9EA106E28C; Tue, 3 Sep 2019 07:29:04 +0000 (UTC) Received: from ming.t460p (ovpn-8-25.pek2.redhat.com [10.72.8.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D14055D9E1; Tue, 3 Sep 2019 07:28:54 +0000 (UTC) Date: Tue, 3 Sep 2019 15:28:49 +0800 From: Ming Lei To: Daniel Lezcano Cc: Thomas Gleixner , 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 Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism Message-ID: <20190903072848.GA22170@ming.t460p> References: <20190827225827.GA5263@ming.t460p> <20190828110633.GC15524@ming.t460p> <20190828135054.GA23861@ming.t460p> <20190903033001.GB23861@ming.t460p> <299fb6b5-d414-2e71-1dd2-9d6e34ee1c79@linaro.org> <20190903063125.GA21022@ming.t460p> <6b88719c-782a-4a63-db9f-bf62734a7874@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <6b88719c-782a-4a63-db9f-bf62734a7874@linaro.org> User-Agent: Mutt/1.11.3 (2019-02-01) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.64]); Tue, 03 Sep 2019 07:29:04 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Sep 03, 2019 at 08:40:35AM +0200, Daniel Lezcano wrote: > On 03/09/2019 08:31, Ming Lei wrote: > > Hi Daniel, > > > > On Tue, Sep 03, 2019 at 07:59:39AM +0200, Daniel Lezcano wrote: > >> > >> Hi Ming Lei, > >> > >> On 03/09/2019 05:30, Ming Lei wrote: > >> > >> [ ... ] > >> > >> > >>>>> 2) irq/timing doesn't cover softirq > >>>> > >>>> That's solvable, right? > >>> > >>> Yeah, we can extend irq/timing, but ugly for irq/timing, since irq/timing > >>> focuses on hardirq predication, and softirq isn't involved in that > >>> purpose. > >>> > >>>> > >>>>> 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? > >>> > >>> Yeah, I have looked at the code for a while, but I think that irq/timing > >>> could become complicated unnecessarily for covering irq flood detection, > >>> meantime it is much less efficient for detecting IRQ flood. > >> > >> In the series, there is nothing describing rigorously the problem (I can > >> only guess) and why the proposed solution solves it. > >> > >> What is your definition of an 'irq flood'? A high irq load? An irq > >> arriving while we are processing the previous one in the bottom halves? > > > > So far, it means that handling interrupt & softirq takes all utilization > > of one CPU, then processes can't be run on this CPU basically, usually > > sort of CPU lockup warning will be triggered. > > It is a scheduler problem then ? Scheduler can do nothing if the CPU is taken completely by handling interrupt & softirq, so seems not a scheduler problem, IMO. Thanks, Ming