> From: PJ Waskiewicz <[EMAIL PROTECTED]>
> Date: Mon, 18 Jun 2007 11:42:29 -0700
>
> > +
> > + /* The TX queue control structures */
> > + struct net_device_subqueue *egress_subqueue;
> > + int egress_subqueue_count;
>
> Since every net device will have at least one subqueue, I
> would suggest that you do this as follows:
>
> 1) In net_device change the quoted part of the patch above to:
>
> int egress_subqueue_count;
> struct net_device_subqueue egress_subqueue[0];
>
> 2) In alloc_netdev():
>
> Factor (sizeof(struct egress_subqueue) * num_subqueues) into
> the net_device allocation size, place the "priv" area after
> the subqueues.
>
> This will save us pointer dereferences on all of these quite
> common accesses.
I've been thinking about this more today, so please bear with me if I'm
missing something. Right now, with how qdisc_restart() is running, we'd
definitely call netif_subqueue_stopped(dev, skb->queue_mapping) for all
multi-ring and single-ring devices. However, with Jamal's and Krishna's
qdisc_restart() rewrite patch, the checks for netif_queue_stopped() and
netif_subqueue_stopped() would be pushed into the qdisc's ->dequeue()
functions. If that's the case, then the only checks on
egress_subqueue[x] would be for multi-ring adapters, or if someone was
silly enough to load sch_{rr|prio} onto a single-ring device with
multiqueue hardware support compiled in. Given all of that, I'm not
sure allocating egress_subqueue[0] at compile time or runtime would make
any difference either way. If I'm missing something, please let me know
- I'd like to reduce any unnecessary pointer dereferences if possible,
but given the proposed qdisc_restart(), I think the code as-is would be
ok.
Thanks,
-PJ Waskiewicz
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