Re: [PATCH] pkt_sched: QFQ Plus: fair-queueing service at DRR cost

From: David Miller
Date: Tue Nov 20 2012 - 13:53:59 EST


From: Paolo Valente <paolo.valente@xxxxxxxxxx>
Date: Tue, 20 Nov 2012 18:45:13 +0100

> - struct sk_buff *skb;
> + struct sk_buff *skb = NULL;

This is not really an improvement, now the compiler can think
that NULL is passed eventually into qdisc_bstats_update().

Please make the logic easier for the compiler to digest.

For example, restructure the top-level logic into something like:

skb = NULL;
if (!list_empty(&in_serv_agg->active))
skb = qfq_peek_skb(in_serv_agg, &cl, &len);
else
len = 0; /* no more active classes in the in-service agg */

if (len == 0 || in_serv_agg->budget < len) {
...
/*
* If we get here, there are other aggregates queued:
* choose the new aggregate to serve.
*/
in_serv_agg = q->in_serv_agg = qfq_choose_next_agg(q);
skb = qfq_peek_skb(in_serv_agg, &cl, &len);
}
if (!skb)
return NULL;

That way it is clearer, to both humans and the compiler, what is
going on here.

Thanks.
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