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,URIBL_BLOCKED,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 3F994C3A5AB for ; Wed, 4 Sep 2019 19:47:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 236DF21726 for ; Wed, 4 Sep 2019 19:47:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729125AbfIDTrR (ORCPT ); Wed, 4 Sep 2019 15:47:17 -0400 Received: from mail-pf1-f194.google.com ([209.85.210.194]:43037 "EHLO mail-pf1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727562AbfIDTrQ (ORCPT ); Wed, 4 Sep 2019 15:47:16 -0400 Received: by mail-pf1-f194.google.com with SMTP id d15so4447949pfo.10; Wed, 04 Sep 2019 12:47:16 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=eVl+9tAIHMvBrQx3eBUEyjTBamIfURj9LIAwDSTkbB0=; b=H68lfn27AU639Ja/djh2IG9+Mv7q0Foy2QH/tXbmyul7u68uwW/FqLmkEov66r950n QmoNKD2KYsUYdw5CSWVkW9KZRt1+mRnuxgMJ1Pm4PZBmhcLSVAkpvmDZjI9nWFlLhi3q 0QTHcQACYpHH+D/Jcibcfee5LwV8RW3QbMrqPupSZAll5xHQqUvAFHtFXI9gkY6mHTKs UkmprGsbjBFvi74exCiQArhkpFbVQISFnY+KsSBCDJPcMyimQ7uErWGUbsc9scNOSQZf 9+2O2AYnIm6iM1Xw2KLY8VSSWHF08yK9CRBPvE18b1i64vwqUSC8L882LFgAatxcoQld TTSQ== X-Gm-Message-State: APjAAAX5ddMCxo6/CX1fDEXa9kxfgV13StKLUi1dLwTyokGtDwEC6+X/ rAB4KKsrj4Dpt2zrNzobPCk= X-Google-Smtp-Source: APXvYqx+3PI2yKaiUlmIJkEhbY9ZelMh9dTSVitv6do41wzJeS7xqPQb6h7FvJuVpl5L7IOgn6YEcw== X-Received: by 2002:a63:31c1:: with SMTP id x184mr37650267pgx.128.1567626435911; Wed, 04 Sep 2019 12:47:15 -0700 (PDT) Received: from desktop-bart.svl.corp.google.com ([2620:15c:2cd:202:4308:52a3:24b6:2c60]) by smtp.gmail.com with ESMTPSA id m19sm41874829pff.108.2019.09.04.12.47.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Sep 2019 12:47:15 -0700 (PDT) Subject: Re: [PATCH 1/4] softirq: implement IRQ flood detection mechanism To: Peter Zijlstra Cc: Daniel Lezcano , Ming Lei , 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 References: <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> <20190904180211.GX2332@hirez.programming.kicks-ass.net> From: Bart Van Assche Message-ID: <9b924e48-e217-9c11-c1fb-46c92a82ea2d@acm.org> Date: Wed, 4 Sep 2019 12:47:13 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190904180211.GX2332@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org 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? Does anyone know which CPUs the following text from Documentation/admin-guide/kernel-parameters.txt refers to? tsc= [ ... ] [x86] noirqtime: Do not use TSC to do irq accounting. Used to run time disable IRQ_TIME_ACCOUNTING on any platforms where RDTSC is slow and this accounting can add overhead. Bart.