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=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 1E538C6778D for ; Tue, 11 Sep 2018 12:16:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CED0020866 for ; Tue, 11 Sep 2018 12:16:10 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CED0020866 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com 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 S1727788AbeIKRPN (ORCPT ); Tue, 11 Sep 2018 13:15:13 -0400 Received: from mga17.intel.com ([192.55.52.151]:59277 "EHLO mga17.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726647AbeIKRPM (ORCPT ); Tue, 11 Sep 2018 13:15:12 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga107.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 11 Sep 2018 05:15:52 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.53,360,1531810800"; d="scan'208";a="89459500" Received: from stinkbox.fi.intel.com (HELO stinkbox) ([10.237.72.174]) by orsmga001.jf.intel.com with SMTP; 11 Sep 2018 05:15:49 -0700 Received: by stinkbox (sSMTP sendmail emulation); Tue, 11 Sep 2018 15:15:48 +0300 Date: Tue, 11 Sep 2018 15:15:48 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Thomas Gleixner Cc: LKML , Dou Liyang , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra Subject: Re: [PATCH] Revert "x86/tsc: Consolidate init code" Message-ID: <20180911121548.GW5565@intel.com> References: <20180910121925.27682-1-ville.syrjala@linux.intel.com> <20180910140710.GR5565@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: 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 On Mon, Sep 10, 2018 at 06:53:54PM +0200, Thomas Gleixner wrote: > On Mon, 10 Sep 2018, Ville Syrjälä wrote: > > Good: 1718674.70 BogoMIPS (lpj=2863311530) > Bad: 859455.59 BogoMIPS (lpj=1431852151) > > while both kernels agree on the CPU frequency of 996MHz. This pretty much > smells like the 32bit LPJ conversion bug which got fixed in rc3. Does the > problem persist with rc3? Indeed looks to be fixed by commit 17f6bac22493 ("x86/tsc: Prevent result truncation on 32bit"). I both cherry-picked that on top of rc2 to make sure it really is that commit, and also tested plain rc3 to make sure it still works. And comparing the bogomips between the three relevant commits makes the bug pretty obvious in hindsight: Calibrating delay loop (skipped), value calculated using timer frequency.. 1718674.70 BogoMIPS (lpj=2863311530) Calibrating delay loop (skipped), value calculated using timer frequency.. 859455.59 BogoMIPS (lpj=1431852151) Calibrating delay loop (skipped), value calculated using timer frequency.. 1994.50 BogoMIPS (lpj=3322410) I suppose we just got very lucky with older kernels. -- Ville Syrjälä Intel