From: Stephen Hemminger <shemminger@vyatta•com>
To: Cong Wang <amwang@redhat•com>
Cc: David Miller <davem@davemloft•net>,
Eric Dumazet <dada1@cosmosbay•com>,
netdev@vger•kernel.org
Subject: Re: [RFC net-next] netpoll: use static branch
Date: Wed, 19 Sep 2012 13:00:59 -0700 [thread overview]
Message-ID: <20120919130059.7b7ebc83@s6510.linuxnetplumber.net> (raw)
In-Reply-To: <1348030210.11754.7.camel@cr0>
On Wed, 19 Sep 2012 12:50:10 +0800
Cong Wang <amwang@redhat•com> wrote:
> On Tue, 2012-09-18 at 14:10 -0700, Stephen Hemminger wrote:
> > This is an attempt to optimize netpoll when not used.
> >
> > Since distro's enable everything and netpoll is only occasionally
> > used, improve performance by getting netpoll condition check
> > out of the Rx fastpath.
> >
> > Compile tested only, I have no real use for netpoll.
> >
> > Signed-off-by: Stephen Hemminger <shemminger@vyatta•com>
> >
> >
> > ---
> > include/linux/netpoll.h | 28 ++++++++++++++++++++--------
> > net/core/netpoll.c | 8 +++++++-
> > 2 files changed, 27 insertions(+), 9 deletions(-)
> >
> > --- a/include/linux/netpoll.h 2012-09-18 13:25:15.575750004 -0700
> > +++ b/include/linux/netpoll.h 2012-09-18 13:29:16.245323347 -0700
> > @@ -66,10 +66,16 @@ static inline void netpoll_send_skb(stru
> >
> >
> > #ifdef CONFIG_NETPOLL
> > +extern struct static_key netpoll_needed;
> > +
> > static inline bool netpoll_rx_on(struct sk_buff *skb)
> > {
> > - struct netpoll_info *npinfo = rcu_dereference_bh(skb->dev->npinfo);
> > + struct netpoll_info *npinfo;
> > +
> > + if (static_key_true(&netpoll_needed))
> > + return false;
> >
>
> I think we should use static_key_false() here, as netpoll is an
> "unlikely" code path.
>
> Using static branch is a good idea though.
>
> Thanks.
But static_key_true is just a wrapper around !static_key_false()
next prev parent reply other threads:[~2012-09-19 20:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-18 21:10 [RFC net-next] netpoll: use static branch Stephen Hemminger
2012-09-19 4:50 ` Cong Wang
2012-09-19 20:00 ` Stephen Hemminger [this message]
2012-09-20 7:30 ` Cong Wang
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