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=-0.9 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS, URIBL_BLOCKED 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 0C9FAC43334 for ; Sat, 1 Sep 2018 21:39:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9F83A2083C for ; Sat, 1 Sep 2018 21:39:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="QNPGUg40" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9F83A2083C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.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 S1727255AbeIBBwN (ORCPT ); Sat, 1 Sep 2018 21:52:13 -0400 Received: from mail-it0-f68.google.com ([209.85.214.68]:32779 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727045AbeIBBwN (ORCPT ); Sat, 1 Sep 2018 21:52:13 -0400 Received: by mail-it0-f68.google.com with SMTP id j198-v6so8022517ita.0 for ; Sat, 01 Sep 2018 14:38:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=GkTMCcglEBhcl1YvI/gHbFFZsQjLvmpgheBH3+VO98w=; b=QNPGUg40dTUDloTXgGYbuFXGEImS2PfyUQ+dSwZU2isYyTrU5TIH5RB0K14im5ekrU +Nrk26aG/nRQAUXwFfdrvjJSvnHJdg38QKs7C90kjWpThzuMA2oyRZOfS/HNgmg4qoFM MXQsnOaH1pcClCEsuSlFlMRYrpmB0iByHAPOM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=GkTMCcglEBhcl1YvI/gHbFFZsQjLvmpgheBH3+VO98w=; b=l1aEObMzAwHlTfQCWpnq0mHM48e6p/rjMelyEmiKIaEts2LtHJYj/VrGYo4kFExMUw q1mTsI9X6c6yte2A4jWV4HXxhzvqTiiPBIvk9sQ0uyJGNoOCn0Px+Rgt0hD1tYa3Kx/1 0JLlIXNaAZ/ZdUJyQzDm/fX878QJYHl0GKYVD9mXGPK6BzGp4trlBNeURImMzSmZC15t rdQbJiHH4AXjoFIfMpn03Aua3Djo7o++PQUujZahAsPVlVABr2hmP/i1cmvgHRNyS/fW DJWyxllQELk9k+OiOpFE1VjKOHPn8HMOLz8Mc5bd/9iZp3FzhZ8KsE+v+i4TGIu4558+ wrmA== X-Gm-Message-State: APzg51DgEAdV7mra7TNODRIb5LxO1rvaGFB1tKHWN9GcoD8nkfxOEoF7 G14tq53YNMVp+nm2XQfew+4f3RZubmlDZUWuwLk= X-Google-Smtp-Source: ANB0VdYnB/D6k3xoiCv5X9hW9mgakolSahbYzgnxPB4iHtrbBT6xgxiam/I0JQH2rpOHZqH4Daj53bl82905koBp2JU= X-Received: by 2002:a02:702:: with SMTP id f2-v6mr16499858jaf.70.1535837934711; Sat, 01 Sep 2018 14:38:54 -0700 (PDT) MIME-Version: 1.0 References: In-Reply-To: From: Linus Torvalds Date: Sat, 1 Sep 2018 14:38:43 -0700 Message-ID: Subject: Re: Redoing eXclusive Page Frame Ownership (XPFO) with isolated CPUs in mind (for KVM to isolate its guests per CPU) To: jsteckli@amazon.de Cc: David Woodhouse , Konrad Rzeszutek Wilk , juerg.haefliger@hpe.com, deepa.srinivasan@oracle.com, Jim Mattson , Andrew Cooper , Linux Kernel Mailing List , Boris Ostrovsky , linux-mm , Thomas Gleixner , joao.m.martins@oracle.com, pradeep.vincent@oracle.com, Andi Kleen , Khalid Aziz , kanth.ghatraju@oracle.com, Liran Alon , Kees Cook , Kernel Hardening , chris.hyser@oracle.com, Tyler Hicks , John Haxby , Jon Masters Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Aug 31, 2018 at 12:45 AM Julian Stecklina wrote: > > I've been spending some cycles on the XPFO patch set this week. For the > patch set as it was posted for v4.13, the performance overhead of > compiling a Linux kernel is ~40% on x86_64[1]. The overhead comes almost > completely from TLB flushing. If we can live with stale TLB entries > allowing temporary access (which I think is reasonable), we can remove > all TLB flushing (on x86). This reduces the overhead to 2-3% for > kernel compile. I have to say, even 2-3% for a kernel compile sounds absolutely horrendous. Kernel bullds are 90% user space at least for me, so a 2-3% slowdown from a kernel is not some small unnoticeable thing. Linus