On Wed, 09 Mar 2016 16:03:20 -0500 (EST)
David Miller <da...@davemloft.net> wrote:
> From: Alexander Duyck <alexander.du...@gmail.com>
> Date: Wed, 9 Mar 2016 08:47:58 -0800
>
> > On Wed, Mar 9, 2016 at 3:00 AM, Jesper Dangaard Brouer
> > <bro...@redhat.com> wrote:
> >> Passing the budget down was Alex'es design. Axel any thoughts?
> >
> > I'd say just use dev_consume_skb_any in the bulk free instead of
> > dev_consume_skb_irq. This is slow path, as you said, so it shouldn't
> > come up often.
>
> Agreed.
>
> >> I do wonder how expensive this check is... as it goes into a code
> >> hotpath, which is very unlikely. The good thing would be, that we
> >> handle if buggy drivers call this function from a none softirq context
> >> (as these bugs could be hard to catch).
> >>
> >> Can netpoll ever be called from softirq or with BH disabled? (It
> >> disables IRQs, which would break calling kmem_cache_free_bulk).
> >
> > It is better for us to switch things out so that the napi_consume_skb
> > is the fast path with dev_consume_skb_any as the slow. There are too
> > many scenarios where we could be invoking something that makes use of
> > this within the Tx path so it is probably easiest to just solve it
> > that way so we don't have to deal with it again in the future.
>
> Indeed.
So, if I understand you correctly, then we drop the budget parameter
and check for in_softirq(), like:
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7af7ec635d90..a3c61a9b65d2 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -796,14 +796,14 @@ void __kfree_skb_defer(struct sk_buff *skb)
_kfree_skb_defer(skb);
}
-void napi_consume_skb(struct sk_buff *skb, int budget)
+void napi_consume_skb(struct sk_buff *skb)
{
if (unlikely(!skb))
return;
- /* if budget is 0 assume netpoll w/ IRQs disabled */
- if (unlikely(!budget)) {
- dev_consume_skb_irq(skb);
+ /* Handle if not called from NAPI context, and netpoll invocation */
+ if (unlikely(!in_softirq())) {
+ dev_consume_skb_any(skb);
return;
}
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
