From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [PATCH] pkt_sched: enable QFQ to support TSO/GSO Date: Tue, 6 Nov 2012 09:30:57 +0100 Message-ID: <20121106093057.465c5b6c@s6510.linuxnetplumber.net> References: <20121106062924.GA2930@paolo-ThinkPad-W520> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: jhs@mojatatu.com, davem@davemloft.net, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, rizzo@iet.unipi.it, fchecconi@gmail.com To: Paolo Valente Return-path: In-Reply-To: <20121106062924.GA2930@paolo-ThinkPad-W520> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Tue, 6 Nov 2012 07:29:24 +0100 Paolo Valente wrote: > If the max packet size for some class (configured through tc) is > violated by the actual size of the packets of that class, then QFQ > would not schedule classes correctly, and the data structures > implementing the bucket lists may get corrupted. This problem occurs > with TSO/GSO even if the max packet size is set to the MTU, and is, > e.g., the cause of the failure reported in [1]. Two patches have been > proposed to solve this problem in [2], one of them is a preliminary > version of this patch. > > This patch addresses the above issues by: 1) setting QFQ parameters to > proper values for supporting TSO/GSO (in particular, setting the > maximum possible packet size to 64KB), 2) automatically increasing the > max packet size for a class, lmax, when a packet with a larger size > than the current value of lmax arrives. > > The drawback of the first point is that the maximum weight for a class > is now limited to 4096, which is equal to 1/16 of the maximum weight > sum. > > Finally, this patch also forcibly caps the timestamps of a class if > they are too high to be stored in the bucket list. This capping, taken > from QFQ+ [3], handles the unfrequent case described in the comment to > the function slot_insert. > > [1] http://marc.info/?l=linux-netdev&m=134968777902077&w=2 > [2] http://marc.info/?l=linux-netdev&m=135096573507936&w=2 > [3] http://marc.info/?l=linux-netdev&m=134902691421670&w=2 > > Signed-off-by: Paolo Valente > Tested-by: Cong Wang > Acked-by: Stephen Hemminger Acked-by: Stephen Hemminger