From owner-freebsd-stable@freebsd.org Mon Aug 14 05:08:33 2017 Return-Path: Delivered-To: freebsd-stable@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id A6FC0DD47E3 for ; Mon, 14 Aug 2017 05:08:33 +0000 (UTC) (envelope-from kob6558@gmail.com) Received: from mail-ua0-x233.google.com (mail-ua0-x233.google.com [IPv6:2607:f8b0:400c:c08::233]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 642DF6D039 for ; Mon, 14 Aug 2017 05:08:33 +0000 (UTC) (envelope-from kob6558@gmail.com) Received: by mail-ua0-x233.google.com with SMTP id w45so32803695uac.5 for ; Sun, 13 Aug 2017 22:08:33 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:sender:in-reply-to:references:from:date:message-id :subject:to:cc; bh=n6szXHBmvRfI9Qq82Nt8sBJ88QAbAcxvymlPy9Fs4nA=; b=oDKC3keFv/4SbadgusoI9X1w3SbTBfqkMeY2OFbXftiP5JOKQgE05Syzn5PlYgUQwj +P3zOPiPKB5M8zCzHCTdJupXznGycLnV68cc5UdhXKfMN4+riNu8xCxAMRbm2XA2jx8Y coKAk1hzBY2ZFFckT6bZpbToL5GDPRgfgw+GOJQcT1Xl4kJbYgbHcaZ89LjTqMOJC5Ta ALh0cxiTtUXq1k4HnlwJzlSIGuwePxncMT9pfjBJNtMIjk8RG24tyV26A0j8gu/Fkmk8 surx4PpY20btIPHWx2L2K2gUwqGCjJgi+n+6G3a1X9EIqn+IRwpvSBEtLxZAlwIXkBq/ 6R1A== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:sender:in-reply-to:references:from :date:message-id:subject:to:cc; bh=n6szXHBmvRfI9Qq82Nt8sBJ88QAbAcxvymlPy9Fs4nA=; b=kP1KwirRsUXjU2SDrlUgATYatLS+GjaFed2Efucsgg7OskEsIPE+JHkoY4cOrLD4BP vjWTxa6H35IxhJNjU3XnuRScMf0qRUFbv9624ZHR1Q7Hvvt2Fe/fY5SgMieGydVMNL4M ZgMUQpUGeJr5k0AXIXxjdciBEy4laVtHhxl3zY9XBkvA05a+Y/KYD6dqY5oNS1kaU0jL yJGXmEqC9mITrC4otazPFMv8keWerZvwqEvtU4uh7H0mk9e7LtqER77NBOYRD9qufl7g h6gTCba7jWsfra8nbe0NtveroNAPJFPSAlSR19D9UQmQnOhZoCivM8ZBTgq/8pnbG8f5 x7ZA== X-Gm-Message-State: AHYfb5hgPiTu5J/me1zO8QqVaprvlACBipX/FRRFC3Q0g4Nl+F1H4y8k VOFnLBxgeEJLJPWOLprgq2yGiSftcWj7VLM= X-Received: by 10.176.80.193 with SMTP id d1mr16264230uaa.124.1502687312419; Sun, 13 Aug 2017 22:08:32 -0700 (PDT) MIME-Version: 1.0 Sender: kob6558@gmail.com Received: by 10.103.76.143 with HTTP; Sun, 13 Aug 2017 22:08:31 -0700 (PDT) In-Reply-To: References: From: Kevin Oberman Date: Sun, 13 Aug 2017 22:08:31 -0700 X-Google-Sender-Auth: 1hrdrvuMvU9433HsnEKm0UCy7-U Message-ID: Subject: Re: TSC timekeeping and cpu states To: Aristedes Maniatis Cc: freebsd-stable Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.23 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 14 Aug 2017 05:08:33 -0000 On Sun, Aug 13, 2017 at 8:25 PM, Aristedes Maniatis wrote: > I note that in FreeBSD 11, we now have this: > > # grep performance_cx_lowest /etc/defaults/rc.conf > performance_cx_lowest="C2" # Online CPU idle state > > However this wiki page suggests that C1 is the default > > https://wiki.freebsd.org/TuningPowerConsumption > > > Are these inconsistent? > > > I went looking for this because I've been having trouble with the TSC-low > timecounter hardware choice and my system clock running at about 80% of > normal speed. Moving to ACPI-fast solved this problem. > > Could the power saving CPU states be related to this problem, or should I > look elsewhere for the TSC issue? > > This is a server, not a laptop. > > > Thanks > Ari > > > > -- > --------------------------> > Aristedes Maniatis > CEO, ish > https://www.ish.com.au > GPG fingerprint CBFB 84B4 738D 4E87 5E5C 5EFA EF6A 7D2E 3E49 102A > Again, the documentation lags reality. The default was changed for 11.0. It is still conservative. In ALMOST all cases, Cmax will yield the bast results. However, on large systems with many cores, Cmax will trigger very poor results, so the default is C2, just to be safe. As far as possible TSC impact, I think older processors had TSC issues when not all cores ran with the same clock speed. That said, I am not remotely expert on such issues, so don't take this too seriously. -- Kevin Oberman, Part time kid herder and retired Network Engineer E-mail: rkoberman@gmail.com PGP Fingerprint: D03FB98AFA78E3B78C1694B318AB39EF1B055683