Re: [PATCH RFC] pkt_sched: enable QFQ to support TSO/GSO

[Paolo Valente]

Il 29/10/2012 12:08, Cong Wang ha scritto:
> On 10/29/2012 04:51 PM, Paolo Valente 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 (a notification is also appended
> > to the log).
> >
> > 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@xxxxxxxxxx>
>
>
> Please respect people who helps you to test it:
>
> Tested-by: Cong Wang <amwang@xxxxxxxxxx>
Oops, really sorry about that. I did not mean to hide your contribution. 
I am just not familiar with the process.
> I tested it again just in case...
Thanks again
> By the way, one nit below:
>
>
> > +    if (unlikely(cl->lmax < qdisc_pkt_len(skb))) {
> > +        pr_notice("qfq: increasing maxpkt from %u to %u for class %u",
> > +              cl->lmax, qdisc_pkt_len(skb), cl->common.classid);
> > +        qfq_update_reactivate_class(q, cl, cl->inv_w,
> > +                        qdisc_pkt_len(skb), 0);
> > +    }
>
>
> Seems the log level KERN_NOTICE is overkill, normal users don't care
> about these information, so s/pr_notice/pr_debug/.
Thanks, I will integrate this and possible other suggestions in a new 
version of the patch.
> Thanks!


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| Paolo Valente              |                            |
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