On Sat, 21 Mar 2009, David Miller wrote:
> From: "Waskiewicz Jr, Peter P" <[email protected]>
> Date: Fri, 20 Mar 2009 23:21:38 -0700 (Pacific Daylight Time)
>
> > I see your point, but it is a hack in my opinion. The device will have 8
> > real Tx queues, not 1. I'd much rather go with the original proposal,
> > since if the code in dev_pick_tx() changed, it could silently break ixgbe.
>
> It can't, if you only advertise one transmit queue the kernel
> can never ever choose anything other than queue zero. It's
> impossible.
>
> Stephen's right, you guys don't need your select queue override.
>
> And if you recall I suspected this from the very beginning.
>
> You guys never ever think out of the box, ever... if it's
> not straightforward, you guys won't got for it. That makes
> it very frustrating to get anything done.
This patch will break DCB in ixgbe. We need all 8 queues, because the
user will be assigning tc filters to the sch_multiq qdisc to get traffic
into priority queues. If we take Stephen's patch and tell the stack we
have 1 real_num_tx_queues, then we get 1 band in sch_multiq, which makes
it impossible to assign traffic to priorities 1 through 8:
static int multiq_tune(struct Qdisc *sch, struct nlattr *opt)
{
struct multiq_sched_data *q = qdisc_priv(sch);
struct tc_multiq_qopt *qopt;
int i;
if (!netif_is_multiqueue(qdisc_dev(sch)))
return -EOPNOTSUPP;
if (nla_len(opt) < sizeof(*qopt))
return -EINVAL;
qopt = nla_data(opt);
qopt->bands = qdisc_dev(sch)->real_num_tx_queues;
This is not what we want, rather, we want all 8 Tx queues that we expose.
The only reason we override the select_queue is to catch the unfiltered
traffic and send it to queue 0.
Cheers,
-PJ Waskiewicz
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