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From: Alexei Starovoitov <alexei.starovoitov@gmail.com>
To: Stanislav Fomichev <sdf@fomichev.me>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
	Stanislav Fomichev <sdf@google.com>,
	Network Development <netdev@vger.kernel.org>,
	David Miller <davem@davemloft.net>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	simon.horman@netronome.com, Willem de Bruijn <willemb@google.com>
Subject: Re: [RFC bpf-next 0/7] net: flow_dissector: trigger BPF hook when called from eth_get_headlen
Date: Tue, 5 Feb 2019 16:47:16 -0800	[thread overview]
Message-ID: <20190206004714.pz44evow5uwgvt4x@ast-mbp.dhcp.thefacebook.com> (raw)
In-Reply-To: <20190205204003.GB10769@mini-arch>

On Tue, Feb 05, 2019 at 12:40:03PM -0800, Stanislav Fomichev wrote:
> On 02/05, Willem de Bruijn wrote:
> > On Tue, Feb 5, 2019 at 12:57 PM Stanislav Fomichev <sdf@google.com> wrote:
> > >
> > > Currently, when eth_get_headlen calls flow dissector, it doesn't pass any
> > > skb. Because we use passed skb to lookup associated networking namespace
> > > to find whether we have a BPF program attached or not, we always use
> > > C-based flow dissector in this case.
> > >
> > > The goal of this patch series is to add new networking namespace argument
> > > to the eth_get_headlen and make BPF flow dissector programs be able to
> > > work in the skb-less case.
> > >
> > > The series goes like this:
> > > 1. introduce __init_skb and __init_skb_shinfo; those will be used to
> > >    initialize temporary skb
> > > 2. introduce skb_net which can be used to get networking namespace
> > >    associated with an skb
> > > 3. add new optional network namespace argument to __skb_flow_dissect and
> > >    plumb through the callers
> > > 4. add new __flow_bpf_dissect which constructs temporary on-stack skb
> > >    (using __init_skb) and calls BPF flow dissector program
> > 
> > The main concern I see with this series is this cost of skb zeroing
> > for every packet in the device driver receive routine, *independent*
> > from the real skb allocation and zeroing which will likely happen
> > later.
> Yes, plus ~200 bytes on the stack for the callers.
> 
> Not sure how visible this zeroing though, I can probably try to get some
> numbers from BPF_PROG_TEST_RUN (running current version vs running with
> on-stack skb).

imo extra 256 byte memset for every packet is non starter.


  reply	other threads:[~2019-02-06  0:47 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-05 17:36 [RFC bpf-next 0/7] net: flow_dissector: trigger BPF hook when called from eth_get_headlen Stanislav Fomichev
2019-02-05 17:36 ` [RFC bpf-next 1/7] net: introduce __init_skb and __init_skb_shinfo helpers Stanislav Fomichev
2019-02-05 20:18   ` Willem de Bruijn
2019-02-05 17:36 ` [RFC bpf-next 2/7] net: introduce skb_net helper Stanislav Fomichev
2019-02-05 20:19   ` Willem de Bruijn
2019-02-05 20:42     ` Stanislav Fomichev
2019-02-05 17:36 ` [RFC bpf-next 3/7] net: plumb network namespace into __skb_flow_dissect Stanislav Fomichev
2019-02-05 20:19   ` Willem de Bruijn
2019-02-05 20:40     ` Stanislav Fomichev
2019-02-05 17:36 ` [RFC bpf-next 4/7] net: flow_dissector: handle no-skb use case Stanislav Fomichev
2019-02-05 20:19   ` Willem de Bruijn
2019-02-05 20:45     ` Stanislav Fomichev
2019-02-05 17:36 ` [RFC bpf-next 5/7] bpf: when doing BPF_PROG_TEST_RUN for flow dissector use no-skb mode Stanislav Fomichev
2019-02-05 20:19   ` Willem de Bruijn
2019-02-05 17:36 ` [RFC bpf-next 6/7] selftests/bpf: add flow dissector bpf_skb_load_bytes helper test Stanislav Fomichev
2019-02-05 17:36 ` [RFC bpf-next 7/7] net: flow_dissector: pass net argument to the eth_get_headlen Stanislav Fomichev
2019-02-05 20:18 ` [RFC bpf-next 0/7] net: flow_dissector: trigger BPF hook when called from eth_get_headlen Willem de Bruijn
2019-02-05 20:40   ` Stanislav Fomichev
2019-02-06  0:47     ` Alexei Starovoitov [this message]
2019-02-06  0:59       ` Stanislav Fomichev
2019-02-06  3:12         ` Alexei Starovoitov
2019-02-06  3:56           ` Stanislav Fomichev
2019-02-06  4:11             ` Alexei Starovoitov
2019-02-06  5:49               ` Stanislav Fomichev
2019-02-12 17:02                 ` Stanislav Fomichev
2019-02-14  4:39                   ` Alexei Starovoitov
2019-02-14  5:57                     ` Stanislav Fomichev
2019-02-14  6:38                       ` Alexei Starovoitov
2019-02-14 17:35                         ` Stanislav Fomichev
2019-02-25 20:33                           ` Stanislav Fomichev

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