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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 A1771C3A5A5 for ; Thu, 5 Sep 2019 09:06:51 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 74C732082E for ; Thu, 5 Sep 2019 09:06:51 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="WVnk/2tN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 74C732082E Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=4Qk2xYcC01ZbYCbCZnFsnof2zU0AqqPKejrxioMG7yg=; b=WVnk/2tNeugSJs WufGqOodywSqnwL6moBQ7THqR4FgVXrQ/oyjCu1ebfjRwM5zC6tszVqfmMX91YsM0gaB1DM0lcO8z dObB1Xc0GHf60p7G+OenM/EJqZ9XgNxIw2P1KHXeyuhx2oT1mVUxnfyA3CBeQYLZYkMdJGDzV+q0p epVDGyKl6p5Mzac3A6LY0esbVWhpPWODonqyRsxWITfmRPodjAvtU53iUOK+NA/+qVQerWbWs0COP QL+EdEJmHzWlLvucNEAweXn0fyhGiVeDvgCOOrfj/T7lVnFkqzqr+xWTU/gPHkTimzTcurW0qQxlr +e96nkYTGjpGXIHoEF8A==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1i5niz-0004nT-Mu; Thu, 05 Sep 2019 09:06:41 +0000 Received: from mx1.redhat.com ([209.132.183.28]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i5niw-0004mU-FJ for linux-nvme@lists.infradead.org; Thu, 05 Sep 2019 09:06:40 +0000 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 80E5E8A1C9D; Thu, 5 Sep 2019 09:06:34 +0000 (UTC) Received: from ming.t460p (ovpn-8-16.pek2.redhat.com [10.72.8.16]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4053E5D9CA; Thu, 5 Sep 2019 09:06:23 +0000 (UTC) Date: Thu, 5 Sep 2019 17:06:19 +0800 From: Ming Lei To: Daniel Lezcano Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism Message-ID: <20190905090617.GB4432@ming.t460p> References: <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> <20190903072848.GA22170@ming.t460p> <6f3b6557-1767-8c80-f786-1ea667179b39@acm.org> <2a8bd278-5384-d82f-c09b-4fce236d2d95@linaro.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <2a8bd278-5384-d82f-c09b-4fce236d2d95@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 [10.5.110.69]); Thu, 05 Sep 2019 09:06:34 +0000 (UTC) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190905_020638_529920_9FC4491B X-CRM114-Status: GOOD ( 20.49 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Keith Busch , Hannes Reinecke , Bart Van Assche , linux-scsi@vger.kernel.org, Peter Zijlstra , Long Li , John Garry , LKML , linux-nvme@lists.infradead.org, Jens Axboe , Ingo Molnar , Thomas Gleixner , Christoph Hellwig , Sagi Grimberg Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org On Wed, Sep 04, 2019 at 07:31:48PM +0200, Daniel Lezcano wrote: > Hi, > > On 04/09/2019 19:07, Bart Van Assche wrote: > > On 9/3/19 12:50 AM, Daniel Lezcano wrote: > >> On 03/09/2019 09:28, Ming Lei wrote: > >>> On Tue, Sep 03, 2019 at 08:40:35AM +0200, Daniel Lezcano wrote: > >>>> 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. > >> > >> Why? If there is a irq pressure on one CPU reducing its capacity, the > >> scheduler will balance the tasks on another CPU, no? > > > > Only if CONFIG_IRQ_TIME_ACCOUNTING has been enabled. However, I don't > > know any Linux distro that enables that option. That's probably because > > that option introduces two rdtsc() calls in each interrupt. Given the > > overhead introduced by this option, I don't think this is the solution > > Ming is looking for. > > Was this overhead reported somewhere ? The syscall of gettimeofday() calls ktime_get_real_ts64() which finally calls tk_clock_read() which calls rdtsc too. But gettimeofday() is often used in fast path, and block IO_STAT needs to read it too. > > > See also irqtime_account_irq() in kernel/sched/cputime.c. > > From my POV, this framework could be interesting to detect this situation. Now we are talking about IRQ_TIME_ACCOUNTING instead of IRQ_TIMINGS, and the former one could be used to implement the detection. And the only sharing should be the read of timestamp. Thanks, Ming _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme