From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36486) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ahMcF-00032t-2f for qemu-devel@nongnu.org; Sat, 19 Mar 2016 15:32:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ahMcB-0005nt-R9 for qemu-devel@nongnu.org; Sat, 19 Mar 2016 15:32:51 -0400 Received: from mx1.redhat.com ([209.132.183.28]:57615) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ahMcB-0005nE-Mq for qemu-devel@nongnu.org; Sat, 19 Mar 2016 15:32:47 -0400 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (Postfix) with ESMTPS id 0B74F3B702 for ; Sat, 19 Mar 2016 19:32:45 +0000 (UTC) Received: from localhost (ovpn-204-74.brq.redhat.com [10.40.204.74]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u2JJWifr018912 for ; Sat, 19 Mar 2016 15:32:45 -0400 Date: Sat, 19 Mar 2016 19:32:44 +0000 From: "Richard W.M. Jones" Message-ID: <20160319193243.GA19398@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [Qemu-devel] Is 'hwclock -u -s' in a modern Linux guest necessary? List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org I've been examining the time taken to launch the libguestfs appliance[1]. One of the commands we run in our custom init is: hwclock -u -s This takes 0.3 seconds, which is over 10% of the total launch time, and as far as I can tell it does nothing useful. It was added many years ago, and no one knows what it does. We can assume that we're running a modern Linux guest kernel, recent qemu, have virtio, kvm-clock etc. Is there any need to run this command? Rich. [1] http://libguestfs.org/guestfs-internals.1.html -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com libguestfs lets you edit virtual machines. Supports shell scripting, bindings from many languages. http://libguestfs.org