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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS 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 C3924C2D0D1 for ; Tue, 17 Dec 2019 20:17:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 983FA24650 for ; Tue, 17 Dec 2019 20:17:17 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1576613837; bh=M1c/O0iDEk6T8Gfqt4f5ZxzFfCgxZMruJbN2xwoze1w=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=RKqG3Euan4BHLq5A2Rodtxuvf+fZlyT0xfa6d20b1w5nhqlK/FeOg+2ubfNyYrupd WDDPf7zqDsOobR+OFj+MFR6ENaE/ncskMSRWfMonkuiUSoF8JjHp/6/GsBidcQTmt0 TxxN5N8ApNSuiXK3I/FNGccB2ODMJ+/gLC7a4zj8= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728768AbfLQURQ (ORCPT ); Tue, 17 Dec 2019 15:17:16 -0500 Received: from mail-lf1-f66.google.com ([209.85.167.66]:36471 "EHLO mail-lf1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728718AbfLQURM (ORCPT ); Tue, 17 Dec 2019 15:17:12 -0500 Received: by mail-lf1-f66.google.com with SMTP id n12so7909630lfe.3 for ; Tue, 17 Dec 2019 12:17:10 -0800 (PST) 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=XAjeERk50YhDeYT1JOW5M/FgClTa6Imxci6PQByuhDw=; b=BpI4Cx3VyDVOZ4EPyO3hjdxg3/2CzYOdLTwYIUHWWCcq73CwUM4wszAAN+ldrL0+bB 8R+3ipV3FaxJu6uIhbljBiAFWXXU7/pTjyoWd7Ae/vpY9V90ICMAADQnOReqmRb24gtP cxBovGWS7tf3AdnmbqcJp9hkDnBrrMHrEiOh0= 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=XAjeERk50YhDeYT1JOW5M/FgClTa6Imxci6PQByuhDw=; b=JdIEirkOjO/ZcLBcHz5jmNXZjPqhwrDCluG+AXI3+NHCxKDAjsUCc8JYwnQOnGBJHG 9MypAi7ZLz3wWnvCo9Z1PuNQQO+qZu6M+z4w2YsgoMx76vU6h/A1m/0SwSZqd2Z2u19s 4XjJ+f76Z5qFvoqPoZfWLsYGMwlEA8f1TFSas9g3G4cyDmscqT2UoJz7NL/o1k1hzXGk K/XexScaTYm8GSZK+gfgudWIa636hb0h3ZF9nEUdMk/y2n3H8v5wi9l8ue9dH+XrUsgL hIc/aaaZoBPiHTUnL5C1IdJqNjoR0usq+DuMmYfle+8Y2GrN+lKvkQ/TauMZp0OTA8Ay enXA== X-Gm-Message-State: APjAAAXUxdm7wSgYCgG+dgnxpx1aj9k/bb26KaARPbkeDplSj/6kNYZ6 DXmwFbH8KHSxXvesNcG/YR5lmEEPQkk= X-Google-Smtp-Source: APXvYqxnwDS0O41sCJ5xZUI3g+3lBkZ1oaBI/xz2/dHVAfxRMXXFRrFjAfVyjEq51oizvfLdFf3pPw== X-Received: by 2002:ac2:4884:: with SMTP id x4mr3851949lfc.92.1576613829904; Tue, 17 Dec 2019 12:17:09 -0800 (PST) Received: from mail-lf1-f46.google.com (mail-lf1-f46.google.com. [209.85.167.46]) by smtp.gmail.com with ESMTPSA id m13sm11173505lfo.40.2019.12.17.12.17.08 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Dec 2019 12:17:09 -0800 (PST) Received: by mail-lf1-f46.google.com with SMTP id 15so7918564lfr.2 for ; Tue, 17 Dec 2019 12:17:08 -0800 (PST) X-Received: by 2002:ac2:465e:: with SMTP id s30mr4008826lfo.134.1576613828695; Tue, 17 Dec 2019 12:17:08 -0800 (PST) MIME-Version: 1.0 References: <20191217115547.GA68104@gmail.com> <20191217193039.GF2844@hirez.programming.kicks-ass.net> In-Reply-To: <20191217193039.GF2844@hirez.programming.kicks-ass.net> From: Linus Torvalds Date: Tue, 17 Dec 2019 12:16:52 -0800 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [GIT PULL] timer fixes To: Peter Zijlstra Cc: Ingo Molnar , Linux Kernel Mailing List , Thomas Gleixner , Andrew Morton , Borislav Petkov 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 Tue, Dec 17, 2019 at 11:30 AM Peter Zijlstra wrote: > > What alternatives are there? That is, we normally only use HPET to > double check nobody messed up the TSC. The thing is HPET seems to be _less_ reliable than the TSC we're checking these days. If that's the only use-case for HPET, we should just stop doing it. > We can't just blindly trust TSC across everything x86. No, but we can trust it when it's a modern CPU. The HPET seems to get disabled on all the modern platforms, why do we even have it enabled by default? We should do the HPET cross-check only when we know the TSC might be unreliable, I suspect. Linus