From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [RFC 0/4] net: enable timestamps on a per-socket basis Date: Mon, 21 Apr 2008 04:51:22 -0700 (PDT) Message-ID: <20080421.045122.239401136.davem@davemloft.net> References: <87y7777ahj.fsf@basil.nowhere.org> <20080421.035939.37324583.davem@davemloft.net> <480C7DE3.5020301@firstfloor.org> Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit Cc: juhlenko@akamai.com, netdev@vger.kernel.org, shemminger@linux-foundation.org To: andi@firstfloor.org Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:40784 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754846AbYDULvV (ORCPT ); Mon, 21 Apr 2008 07:51:21 -0400 In-Reply-To: <480C7DE3.5020301@firstfloor.org> Sender: netdev-owner@vger.kernel.org List-ID: From: Andi Kleen Date: Mon, 21 Apr 2008 13:43:31 +0200 > Are you sure they don't just need end2end timestamps as in from sendmsg > to recvmsg()? Imagine the packet is stuck for some time in the > kernel for whatever reason and you only process it later in user space > wouldn't you consider that older time stamp "inaccurate" too? I would, > unless I was debugging the network stack. They need the exact timestamp when the packet was received at the physical machine (and this pretty much means the network card) so that they know precisely when customer X's trade order arrived for scheduling and prioritizing purposes. > It is hard to imagine they really care about excluding one set of queues > (kernel queue) and not other queues (nic rx/tx queues, switch queues > etc.) for their time stamps as you imply. They do.