From owner-freebsd-current@FreeBSD.ORG Wed Apr 16 08:03:40 2008 Return-Path: Delivered-To: current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id A2D941065670; Wed, 16 Apr 2008 08:03:40 +0000 (UTC) (envelope-from derek@computinginnovations.com) Received: from betty.computinginnovations.com (mail.computinginnovations.com [64.81.227.250]) by mx1.freebsd.org (Postfix) with ESMTP id 3C3B68FC1D; Wed, 16 Apr 2008 08:03:39 +0000 (UTC) (envelope-from derek@computinginnovations.com) Received: from p28.computinginnovations.com (dhcp-10-20-30-100.computinginnovations.com [10.20.30.100]) (authenticated bits=0) by betty.computinginnovations.com (8.14.2/8.14.2) with ESMTP id m3FDvsgZ008705; Tue, 15 Apr 2008 08:57:54 -0500 (CDT) (envelope-from derek@computinginnovations.com) Message-Id: <6.0.0.22.2.20080415085657.024e89d0@mail.computinginnovations.com> X-Sender: derek@mail.computinginnovations.com X-Mailer: QUALCOMM Windows Eudora Version 6.0.0.22 Date: Tue, 15 Apr 2008 08:59:41 -0500 To: Jeff Roberson , gnn@freebsd.org From: Derek Ragona In-Reply-To: <20080414215057.B959@desktop> References: <18431.23276.913397.188219@grasshopper.cs.duke.edu> <20080414215057.B959@desktop> Mime-Version: 1.0 X-Antivirus: avast! (VPS 080415-1, 04/15/2008), Outbound message X-Antivirus-Status: Clean X-Virus-Scanned: ClamAV 0.92.1/6780/Tue Apr 15 04:47:04 2008 on betty.computinginnovations.com X-Virus-Status: Clean X-ComputingInnovations-MailScanner-Information: Please contact the ISP for more information X-MailScanner-ID: m3FDvsgZ008705 X-ComputingInnovations-MailScanner: Found to be clean X-ComputingInnovations-MailScanner-From: derek@computinginnovations.com X-Spam-Status: No Content-Type: text/plain; charset="us-ascii"; format=flowed X-Content-Filtered-By: Mailman/MimeDel 2.1.5 Cc: Andrew Gallatin , current@freebsd.org Subject: Re: TSC Timecounter and multi-core/SMP X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Apr 2008 08:03:40 -0000 At 02:51 AM 4/15/2008, Jeff Roberson wrote: >On Tue, 15 Apr 2008, gnn@freebsd.org wrote: > >>At Fri, 11 Apr 2008 08:34:29 -0400 (EDT), >>Andrew Gallatin wrote: >>> >>> >>>gnn@freebsd.org writes: >>> > Howdy, >>> > >>> > Is the TSC timecounter synchronized across multiple cores and/or >>> > processors? A quick search seems to indicate it's not but I'd like to >>> > find a definitive reference on the TSC. >>> >>>There is a great comment in the OpenSolaris source code talking about >>>TSCs and their behavior on SMP systems. See >>>http://cvs.opensolaris.org/source/xref/onnv/onnv-gate/usr/src/uts/i86pc/os/timestamp.c >> >>Actually this was a very helpful bit of reading. >> >>I also believe that at least per processor there is only 1 TSC, that >>is, on a 2 or 4 core, all cores share the same TSC. > >I think we should confirm whether this is the case with earlier opterson. >I have seen two processors on the same die out of sync. > >Jeff I have seen proposed new CPU designs will have the separate cores independently clocked. It will be another extension of power management to enable cores to "sleep" if not needed, also to allow each core to run at different clocks to allow better heat and power management. -Derek -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.