From: Jesper Dangaard Brouer <jbrouer@redhat.com>
To: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Daniel Borkmann <dborkman@redhat.com>,
linux-next list <linux-next@vger.kernel.org>,
brouer@redhat.com, davem@davemloft.net
Subject: Re: [RFC PATCH net-next] packet: fix using smp_processor_id() in preemptible code
Date: Thu, 12 Dec 2013 08:18:38 +0100 [thread overview]
Message-ID: <20131212081838.2d2eafb9@redhat.com> (raw)
In-Reply-To: <1386892503.2586.13.camel@ThinkPad-T5421>
On Fri, 13 Dec 2013 07:55:03 +0800 Li Zhong <zhong@linux.vnet.ibm.com> wrote:
> On Wed, 2013-12-11 at 10:55 +0100, Daniel Borkmann wrote:
> > On 12/12/2013 07:10 AM, Li Zhong wrote:
[...]
> > > Also, it seems that we could move skb_set_queue_mapping() into
> > > packet_pick_tx_queue(), so we avoid calling it one more time
> > > unnecessarily if we are going into the normal dev_queue_xmit() code
> > > path.
> >
> > I don't agree with that part, I think this can be also beneficiary for
> > packets without direct xmit, as in PF_PACKET we don't have a notion of
> > "flow" but just raw packets instead, and can keep the mapping local
> > depending on the current CPU as we do queue setting elsewhere in the
> > stack just as well.
>
> It seems to me that the newly added xmit in packet_sock is
> dev_queue_xmit() by default, and in this default case, dev_queue_xmit()
> would call netdev_pick_tx(), which would set the skb queue_mapping again
> to override the value based on the current CPU.
Yes, I think you are right, that is also my experience with the code path.
> Or did I miss something here?
A bit related; One thing I'm missing to understand, is why the
RAW/PF_PACKET sockets have a NULL in skb->sk when they reach
__netdev_pick_tx() ? (resulting in they cannot store/cache the queue in
sk_tx_queue_set)
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Sr. Network Kernel Developer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2013-12-12 7:18 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-12-12 6:10 [RFC PATCH net-next] packet: fix using smp_processor_id() in preemptible code Li Zhong
2013-12-11 9:55 ` Daniel Borkmann
2013-12-12 23:55 ` Li Zhong
2013-12-12 7:18 ` Jesper Dangaard Brouer [this message]
2013-12-13 6:41 ` Li Zhong
2013-12-13 7:40 ` Li Zhong
2013-12-11 21:49 ` David Miller
2013-12-12 22:54 ` Li Zhong
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