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Date: Tue, 30 Oct 2012 07:24:15 -0700 From: Stephen Hemminger <shemminger@...tta.com> To: Paolo Valente <paolo.valente@...more.it> Cc: jhs@...atatu.com, davem@...emloft.net, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, rizzo@....unipi.it, fchecconi@...il.com Subject: Re: [PATCH RFC] pkt_sched: enable QFQ to support TSO/GSO On Tue, 30 Oct 2012 07:00:56 +0100 Paolo Valente <paolo.valente@...more.it> wrote: > Hi, > 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 <paolo.valente@...more.it> > Tested-by: Cong Wang <amwang@...hat.com> Acked-by: Stephen Hemminger <shemminger@...tta.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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