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 E7B56C3A5A5 for ; Thu, 5 Sep 2019 09:11:20 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id BB1062145D for ; Thu, 5 Sep 2019 09:11:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732169AbfIEJLU (ORCPT ); Thu, 5 Sep 2019 05:11:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38230 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731167AbfIEJLT (ORCPT ); Thu, 5 Sep 2019 05:11:19 -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 60DC93007C23; Thu, 5 Sep 2019 09:11:19 +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 18A8D5D9CA; Thu, 5 Sep 2019 09:11:08 +0000 (UTC) Date: Thu, 5 Sep 2019 17:11:04 +0800 From: Ming Lei To: Bart Van Assche Cc: Peter Zijlstra , Daniel Lezcano , Keith Busch , Hannes Reinecke , Sagi Grimberg , linux-scsi@vger.kernel.org, Long Li , John Garry , LKML , linux-nvme@lists.infradead.org, Jens Axboe , Ingo Molnar , Thomas Gleixner , Christoph Hellwig Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism Message-ID: <20190905091103.GC4432@ming.t460p> References: <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> <20190904180211.GX2332@hirez.programming.kicks-ass.net> <9b924e48-e217-9c11-c1fb-46c92a82ea2d@acm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <9b924e48-e217-9c11-c1fb-46c92a82ea2d@acm.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-4.5.16 (mx1.redhat.com [10.5.110.40]); Thu, 05 Sep 2019 09:11:19 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 04, 2019 at 12:47:13PM -0700, Bart Van Assche wrote: > On 9/4/19 11:02 AM, Peter Zijlstra wrote: > > On Wed, Sep 04, 2019 at 10:38:59AM -0700, Bart Van Assche wrote: > > > I think it is widely known that rdtsc is a relatively slow x86 instruction. > > > So I expect that using that instruction will cause a measurable overhead if > > > it is called frequently enough. I'm not aware of any publicly available > > > measurement data however. > > > > https://www.agner.org/optimize/instruction_tables.pdf > > > > RDTSC, Ryzen: ~36 > > RDTSC, Skylake: ~20 > > > > Sadly those same tables don't list the cost of actual exceptions or even > > IRET :/ > > Thanks Peter for having looked up these numbers. These numbers are much > better than last time I checked. Ming, would CONFIG_IRQ_TIME_ACCOUNTING help > your workload? In my fio test on azure L80sv2, IRQ_TIME_ACCOUNTING isn't enabled. However the irq flood detection introduces two RDTSC for each do_IRQ(), not see obvious IOPS difference. Thanks, Ming