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=1.3 required=3.0 tests=DKIM_SIGNED,FSL_HELO_FAKE, MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID,URIBL_BLOCKED,USER_AGENT_MUTT 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 714BBECDFB1 for ; Sun, 15 Jul 2018 23:04:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1C2B62089D for ; Sun, 15 Jul 2018 23:04:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="ZUBWwasU" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 1C2B62089D Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727193AbeGOX3E (ORCPT ); Sun, 15 Jul 2018 19:29:04 -0400 Received: from mail-wr1-f67.google.com ([209.85.221.67]:35492 "EHLO mail-wr1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727007AbeGOX3E (ORCPT ); Sun, 15 Jul 2018 19:29:04 -0400 Received: by mail-wr1-f67.google.com with SMTP id a3-v6so20842596wrt.2 for ; Sun, 15 Jul 2018 16:04:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=IZJ4uk9DNbF8pX1cq5sgDSnqdABkYAKdQYntbtXl+LQ=; b=ZUBWwasUv6VPKMgS88O3lr/3mCv7IPqSY0GI8A0f5KzczUzRaNQMjbtDi2/hws+eTQ 8BK4Nti+zEruANcYBDILIxsFUdg2CPYjEmJXuANt9B2yScSWJ5ftD9aAcZm9dfAE0Kpj OrWERNbCOnXxP5QUSUZVjlmEeDv7ekddIyJHPsI4RpEnS1wTok8tDXzSFUaxVXTNVfzo Gp0cOLVs6sxTyaIOpLq4guIv6xl+cBAd8GOKyPk6ffoHmItG1ytwyNY4mAcDl8JI4ils I2tsGTW0FJnTaWtqJ5ewFCVZQF/oA6jCaYwJeX5QMwHyIV+KzufKtv2L9QQcbSHEWFYA N+IQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=IZJ4uk9DNbF8pX1cq5sgDSnqdABkYAKdQYntbtXl+LQ=; b=UE0bsRyl52C20S0cw8TukM2zZcRiiq+inVNfUvw407aOXHJhbEstoSU1cFlMp8AWtq VpnXkUMJzacTqYX7Ygou5sSNwBS73o9sDOpTVOzr409ZvRyps5lY0NlpbixrCz1KG6kI dulEV8R+6RddPEjx/QTUGwxMmGR2jBBL0S4SrdU5x/SgG7K8djaicayo7hWDcDOdgGZq KKjaR9u89SR9X3pVt/vsyX6W0bPnKaelwBWkkznPSfZ9BJQgkZYz2IHr4wKIFlFUPrnt wqaSr5kq2Y2O8spTxu1NK/s+KQfK4uirUIQ39e3Mxi8qe19ECrLhlHrzAGXYWhz9d0Rz Dkgw== X-Gm-Message-State: AOUpUlE09WP8JOmNBveDqqXs06Xp1IRiy2w5LuW/fRKHPJwdHPnm6Gy/ IXTUmz75ciztj1wjlcxGpnM= X-Google-Smtp-Source: AAOMgpfG7/2H7oA8WD8SD5o8YYzCX7nc2Y9uQGadCguUJ94yRjwJm+e2sdLdDjQhbRheXXZ+4yqr5w== X-Received: by 2002:adf:9051:: with SMTP id h75-v6mr10759680wrh.65.1531695872681; Sun, 15 Jul 2018 16:04:32 -0700 (PDT) Received: from gmail.com (2E8B0CD5.catv.pool.telekom.hu. [46.139.12.213]) by smtp.gmail.com with ESMTPSA id f6-v6sm18380957wrp.30.2018.07.15.16.04.31 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Sun, 15 Jul 2018 16:04:32 -0700 (PDT) Date: Mon, 16 Jul 2018 01:04:30 +0200 From: Ingo Molnar To: Rik van Riel Cc: linux-kernel@vger.kernel.org, x86@kernel.org, luto@kernel.org, dave.hansen@intel.com, kernel-team@fb.com, efault@gmx.de, tglx@linutronix.de, songliubraving@fb.com, hpa@zytor.com Subject: Re: [PATCH 7/7] x86,switch_mm: skip atomic operations for init_mm Message-ID: <20180715230430.GD30102@gmail.com> References: <20180710142833.26231-1-riel@surriel.com> <20180710142833.26231-8-riel@surriel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180710142833.26231-8-riel@surriel.com> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Rik van Riel wrote: > + /* > + * Stop remote flushes for the previous mm. > + * Skip the idle task; we never send init_mm TLB flushing IPIs, > + * but the bitmap manipulation can cause cache line contention. > + */ > + if (real_prev != &init_mm) { > + VM_WARN_ON_ONCE(!cpumask_test_cpu(cpu, > + mm_cpumask(real_prev))); > + cpumask_clear_cpu(cpu, mm_cpumask(real_prev)); BTW., could this optimization be (safely) extended to all (or most) !task->mm kernel threads? In particular softirq and threaded irq handlers could benefit greatly I suspect in certain networking intense workloads that happen to active them. Thanks, Ingo