From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: Re: HTB accuracy on 10GbE Date: Mon, 02 Nov 2009 16:43:42 +0100 Message-ID: <4AEEFE2E.7090706@trash.net> References: Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Content-Transfer-Encoding: 7bit Cc: shemminger@vyatta.com, Linux Netdev List , takano-ryousei@aist.go.jp To: Ryousei Takano Return-path: Received: from stinky.trash.net ([213.144.137.162]:53211 "EHLO stinky.trash.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755441AbZKBPnj (ORCPT ); Mon, 2 Nov 2009 10:43:39 -0500 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Ryousei Takano wrote: > Hi Stephen and all, > > I have observed a HTB accuracy problem on the Linux kernel 2.6.30 and > the Myri-10G 10 GbE NIC. > HTB can control the transmission rate at Gigabit speed, however it can > not work well at 10 Gigabit speed. > > I asked Stephen this problem at Japan Linux Symposium. He mentioned a > HTB bug related to the timer granularity. > I want to know what is happen, and what should be do for fixing it. > > Any comments and suggestions will be welcome. > > For more detail, please see the following page: > http://code.google.com/p/pspacer/wiki/HTBon10GbE This is not an easy problem to fix. Userspace, the kernel and the netlink API use 32 bit for timing related values, which is too small to use more than microsecond resolution. All of them need to be converted to use bigger types, additionally some kind of compatibility handling to deal with old iproute versions still using microsecond resolution is required.