From mboxrd@z Thu Jan 1 00:00:00 1970 From: "H. Peter Anvin" Subject: Re: [RFC patch 15/15] LTTng timestamp x86 Date: Mon, 20 Oct 2008 15:29:07 -0700 Message-ID: <48FD0633.70604@zytor.com> References: <20081016232729.699004293@polymtl.ca> <20081016234657.837704867@polymtl.ca> <20081017012835.GA30195@Krystal> <57C9024A16AD2D4C97DC78E552063EA3532D455F@orsmsx505.amr.corp.intel.com> <20081017172515.GA9639@goodmis.org> <57C9024A16AD2D4C97DC78E552063EA3533458AC@orsmsx505.amr.corp.intel.com> <20081017184215.GB9874@Krystal> <1f1b08da0810201438g6a109af5i75b34841462b655d@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Torvalds Cc: john stultz , Mathieu Desnoyers , "Luck, Tony" , Steven Rostedt , Andrew Morton , Ingo Molnar , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , Peter Zijlstra , Thomas Gleixner , David Miller , Ingo Molnar List-Id: linux-arch.vger.kernel.org Linus Torvalds wrote: > > But it's not going to solve the "hey, I have 512 CPU's, they are all on > different boards, and no, they are _not_ synchronized to one global > clock!". > > That's why I'd suggest making _purely_ local time, and then aiming for > something NTP-like. But maybe there are better solutions out there. > At the same time, it would definitely be nice to encourage vendors of large SMP systems to provide a common root crystal (frequency standard) for a single SMP domain. Preferrably a really good one, TCXO or better. -hpa From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from terminus.zytor.com ([198.137.202.10]:36309 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752436AbYJTWcK (ORCPT ); Mon, 20 Oct 2008 18:32:10 -0400 Message-ID: <48FD0633.70604@zytor.com> Date: Mon, 20 Oct 2008 15:29:07 -0700 From: "H. Peter Anvin" MIME-Version: 1.0 Subject: Re: [RFC patch 15/15] LTTng timestamp x86 References: <20081016232729.699004293@polymtl.ca> <20081016234657.837704867@polymtl.ca> <20081017012835.GA30195@Krystal> <57C9024A16AD2D4C97DC78E552063EA3532D455F@orsmsx505.amr.corp.intel.com> <20081017172515.GA9639@goodmis.org> <57C9024A16AD2D4C97DC78E552063EA3533458AC@orsmsx505.amr.corp.intel.com> <20081017184215.GB9874@Krystal> <1f1b08da0810201438g6a109af5i75b34841462b655d@mail.gmail.com> In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-arch-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: john stultz , Mathieu Desnoyers , "Luck, Tony" , Steven Rostedt , Andrew Morton , Ingo Molnar , "linux-kernel@vger.kernel.org" , "linux-arch@vger.kernel.org" , Peter Zijlstra , Thomas Gleixner , David Miller , Ingo Molnar Message-ID: <20081020222907.AZkDHhl0QY4DbQI-3YFS6zfAejD7XUqLeCeeu22fXWA@z> Linus Torvalds wrote: > > But it's not going to solve the "hey, I have 512 CPU's, they are all on > different boards, and no, they are _not_ synchronized to one global > clock!". > > That's why I'd suggest making _purely_ local time, and then aiming for > something NTP-like. But maybe there are better solutions out there. > At the same time, it would definitely be nice to encourage vendors of large SMP systems to provide a common root crystal (frequency standard) for a single SMP domain. Preferrably a really good one, TCXO or better. -hpa