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 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4C0ECC433EF for ; Wed, 8 Dec 2021 09:10:53 +0000 (UTC) Received: from localhost ([::1] helo=shelob.surriel.com) by shelob.surriel.com with esmtp (Exim 4.94.2) (envelope-from ) id 1musxx-000060-P5; Wed, 08 Dec 2021 04:10:21 -0500 Received: from mail-qk1-x731.google.com ([2607:f8b0:4864:20::731]) by shelob.surriel.com with esmtps (TLS1.2) tls TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1musxu-000058-Ke for kernelnewbies@kernelnewbies.org; Wed, 08 Dec 2021 04:10:18 -0500 Received: by mail-qk1-x731.google.com with SMTP id m192so1426798qke.2 for ; Wed, 08 Dec 2021 01:10:17 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=vt-edu.20210112.gappssmtp.com; s=20210112; h=sender:from:to:cc:subject:in-reply-to:references:mime-version:date :message-id; bh=vutFqY0ZTHo8JOAnQkYE1aP8GhO1tTcTsT9w9L82rCw=; b=Wh0AnnpyKTCTAl4L4Hg+tQqumpf+i6VX9GSapJ7plb7VhsYuO5N1YDpY0r1+jaXsPB EzCcRsg/L6OP29IAAZ2xTbeb/BknGcRa+D6ZXjNtROc6CaftcHdk8r+tpQdmasDUzU1/ RbKXkFHobLW/IU0SUgkUpy6hiP0HjJgKp38Oc5+5cf1xpO9Zi7SobSDObSXumMl5wIdH OiFE/XAQ3hWeaXUbHnm2TYR5v5c/LmzF9/2dQ8pIN0W2NFZH9d07lN2t3QBYHHzhgxaH VU6DOTubg2S+9ulSqJwqWbKT1nL8WvDOSQORZtk/+mQhXcJNv+1fdqllZecFB0G9PJAe Mz7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:sender:from:to:cc:subject:in-reply-to:references :mime-version:date:message-id; bh=vutFqY0ZTHo8JOAnQkYE1aP8GhO1tTcTsT9w9L82rCw=; b=VQU2US1petXy2P24s4Jd0bDSUzZCD1K94UA6kONkz3bdhcjQ5lKpxG7vNrpxLggJSp XfjU2Gd7pSmHLlNRgwMQXLyNqfVepQQ+yp3LcKM3AYMuutYeOaFpVxNt348y/f70QcQ1 9A8ekiPnYkMJBqOLNXHwr3ZlMLo0769lRPhhaIdjgvbnDvNSAdVVKkkvTdvVFCcMSh0h aFzoB7BmjqGXjwfozKEQJMA0mc1dY5VMh6z2PCgrM2dsAMpLVd+pW477WmeaDzCy30kO yyOXkZk6DeGmznuSzMgctqP23xBrgS/AdC6sd8oZEqrD6JYQPSD+bIAJcpI9PFAqs2Zu baDg== X-Gm-Message-State: AOAM533J/Weh+K1wqZl1B86Xk577JPWyyvs6xhJeRqqWlysS7JpkL98a Ux/iJgthxtW7D9VoOOgrMipSBQ== X-Google-Smtp-Source: ABdhPJzCPC4yk2O4IeNn0B5Mv+VGpKUAIT/OzYQHqV5gB1lSJoFmc15etvn/Wz0457y42ONq7J3aZw== X-Received: by 2002:a05:620a:3dd:: with SMTP id r29mr5208179qkm.208.1638954615971; Wed, 08 Dec 2021 01:10:15 -0800 (PST) Received: from turing-police ([2601:5c0:c380:d61::359]) by smtp.gmail.com with ESMTPSA id y11sm1423475qta.6.2021.12.08.01.10.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 08 Dec 2021 01:10:15 -0800 (PST) From: "Valdis Kl=?utf-8?Q?=c4=93?=tnieks" X-Google-Original-From: "Valdis Kl=?utf-8?Q?=c4=93?=tnieks" X-Mailer: exmh version 2.10.0-pre 07/05/2021 with nmh-1.7+dev To: Muni Sekhar Subject: Re: Time: new clocksource In-reply-to: References: Mime-Version: 1.0 Date: Wed, 08 Dec 2021 04:10:14 -0500 Message-ID: <158505.1638954614@turing-police> Cc: tglx@linutronix.de, Daniel Lezcano , LKML , kernelnewbies X-BeenThere: kernelnewbies@kernelnewbies.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Learn about the Linux kernel List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kernelnewbies-bounces@kernelnewbies.org On Tue, 07 Dec 2021 13:03:07 +0530, Muni Sekhar said: > Which module is responsible for resulting in the absolute time? Is > absolute time synchronized across multiple systems connected on the > network? man -k ntp Keeping the system clock in sync with external timesources and reality is too complicated and messy to be done inside the kernel, so it's usually done with a userspace daemon which on Linux boxes is usually ntpd. Depending on the clock stability of the hardware, whether you have an RTC chip that keeps track of time even when powered down, and the timing tolerances you want on your network (synced to the same minute, or same second, or same 0.001 seconds), it may be sufficient to run ntpdate at an appropriate time during system boot, or from inside a cron job, or you may want to have a continually running ntpd process. Most sane distros have ntpd enabled by default with a reasonable set of defaults - systems that have non-broken clocks will fairly quickly figure out the clock drift rate, and your network load to keep the clocks within a few milliseconds of a national time standard drops to a few packets every 20 minutes or so. In case of a network outage, it will continue to correct the system clock according to the last known drift rate. And if you need better than millisecond sync, you're going to be springing for a GPS receiver with a PPS output and/or a cesium or rubidium clock. _______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies