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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham 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 16A6AC282E1 for ; Thu, 25 Apr 2019 12:38:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9B9F82067C for ; Thu, 25 Apr 2019 12:38:11 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="F75GqaZ0" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731257AbfDYMiL (ORCPT ); Thu, 25 Apr 2019 08:38:11 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:34550 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725965AbfDYMiJ (ORCPT ); Thu, 25 Apr 2019 08:38:09 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=XqVA4owxqT27GNJpHmX8jhJ7/6kEV8Pt0Cjgq247ZIA=; b=F75GqaZ0A6oPqiHXXkcqEZUNy vN01oasCTw2hO5T9WYTYsdpmSmeGKxDjRjvWjehCxQsfVQPbjhNnENhneodcpMFfI8+HBvhMG9lgr cbQkgELPK0JM/PpPR0GcpEjgjSlCD3GzDkwNSlglBVXoLtKogsozflGgLCqljE8oIJT/Mme2M8kDF 4FDiRrYhzpFqmy3jixzpzyXjxzPsM9aQuLiC3cqRrcA9VkHhhE9rl1v9hmAEGKDFmrDmkPxvtY3xd kQb6UAhbvH0GHU/XsiZX0mrrlE34FkEoPk48GH7xB96C53vevv5ihBdHs54mutkR94Qq9prQQ+NWK KqdqHFx5Q==; Received: from j217100.upc-j.chello.nl ([24.132.217.100] helo=hirez.programming.kicks-ass.net) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJddd-0007Bc-Lv; Thu, 25 Apr 2019 12:38:05 +0000 Received: by hirez.programming.kicks-ass.net (Postfix, from userid 1000) id 179AE29C42D01; Thu, 25 Apr 2019 14:38:04 +0200 (CEST) Date: Thu, 25 Apr 2019 14:38:04 +0200 From: Peter Zijlstra To: Konstantin Khlebnikov Cc: linux-kernel@vger.kernel.org, Len Brown , Frederic Weisbecker , "Rafael J. Wysocki" , Ingo Molnar , Thomas Gleixner , "Paul E. McKenney" Subject: Re: [PATCH RFC] x86 / CPU: Add cpu isolation flag for avoiding disturbance from aperfmperf IPI Message-ID: <20190425123804.GU4038@hirez.programming.kicks-ass.net> References: <155618921176.2006.3031084313219003524.stgit@buzz> <20190425114503.GP4038@hirez.programming.kicks-ass.net> <8b54ebf5-7daf-2760-7210-e0e945014c9e@yandex-team.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8b54ebf5-7daf-2760-7210-e0e945014c9e@yandex-team.ru> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 25, 2019 at 03:27:12PM +0300, Konstantin Khlebnikov wrote: > On 25.04.2019 14:45, Peter Zijlstra wrote: > > On Thu, Apr 25, 2019 at 01:46:51PM +0300, Konstantin Khlebnikov wrote: > > > Sensitive workloads like DPDK polling do not like any interrupts. > > > > > > This patch adds flag 'freq' for boot option 'isolcpu': isolcpu=freq,. > > > > > > Users like show_cpuinfo() fallback to frequency from generic cpufreq > > > policy if arch-specific requesting method returns 0. > > > > Then don't touch that sysfs file? > > What sysfs file? /sys/devices/system/cpu/cpu*/cpufreq/scaling_cur_freq > I mean many applications read /proc/cpuinfo and this triggers IPI to all cpus. Argh, I missed it was wired into that too :/ > > I really hate having an option for just this. > > > > This could be generalized to 'isolate cpu from unnecessary IPI'. > Something like mm pagevec drain also could be avoided. Well, that should be a default feature of nohz full, no additional flags required.