From: "Björn Töpel" <bjorn.topel@intel.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Björn Töpel" <bjorn.topel@gmail.com>,
ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
bpf@vger.kernel.org
Cc: magnus.karlsson@intel.com, maciej.fijalkowski@intel.com,
kuba@kernel.org, jonathan.lemon@gmail.com, maximmi@nvidia.com,
davem@davemloft.net, hawk@kernel.org, john.fastabend@gmail.com,
ciara.loftus@intel.com, weqaar.a.janjua@intel.com
Subject: Re: [PATCH bpf-next v2 4/8] xsk: register XDP sockets at bind(), and add new AF_XDP BPF helper
Date: Wed, 20 Jan 2021 16:18:50 +0100 [thread overview]
Message-ID: <3c6feb0d-6a64-2251-3cac-c79cff29d85c@intel.com> (raw)
In-Reply-To: <87k0s74q1a.fsf@toke.dk>
On 2021-01-20 15:54, Toke Høiland-Jørgensen wrote:
> Björn Töpel <bjorn.topel@intel.com> writes:
>
>> On 2021-01-20 13:50, Toke Høiland-Jørgensen wrote:
>>> Björn Töpel <bjorn.topel@gmail.com> writes:
>>>
>>>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>>>> index c001766adcbc..bbc7d9a57262 100644
>>>> --- a/include/uapi/linux/bpf.h
>>>> +++ b/include/uapi/linux/bpf.h
>>>> @@ -3836,6 +3836,12 @@ union bpf_attr {
>>>> * Return
>>>> * A pointer to a struct socket on success or NULL if the file is
>>>> * not a socket.
>>>> + *
>>>> + * long bpf_redirect_xsk(struct xdp_buff *xdp_md, u64 action)
>>>> + * Description
>>>> + * Redirect to the registered AF_XDP socket.
>>>> + * Return
>>>> + * **XDP_REDIRECT** on success, otherwise the action parameter is returned.
>>>> */
>>>
>>> I think it would be better to make the second argument a 'flags'
>>> argument and make values > XDP_TX invalid (like we do in
>>> bpf_xdp_redirect_map() now). By allowing any value as return you lose
>>> the ability to turn it into a flags argument later...
>>>
>>
>> Yes, but that adds a run-time check. I prefer this non-checked version,
>> even though it is a bit less futureproof.
>
> That...seems a bit short-sighted? :)
> Can you actually see a difference in your performance numbers?
>
I would rather add an additional helper *if* we see the need for flags,
instead of paying for that upfront. For me, BPF is about being able to
specialize, and not having one call with tons of checks.
(Related; Going forward, the growing switch() for redirect targets in
xdp_do_redirect() is a concern for me...)
And yes, even with all those fancy branch predictors, less instructions
is still less. :-) (It shows in my ubenchs.)
Björn
next prev parent reply other threads:[~2021-01-20 15:20 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-19 15:50 [PATCH bpf-next v2 0/8] Introduce bpf_redirect_xsk() helper Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 1/8] xdp: restructure redirect actions Björn Töpel
2021-01-20 12:44 ` Toke Høiland-Jørgensen
2021-01-20 13:40 ` Björn Töpel
2021-01-20 14:52 ` Toke Høiland-Jørgensen
2021-01-20 15:49 ` Björn Töpel
2021-01-20 16:30 ` Toke Høiland-Jørgensen
2021-01-20 17:26 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 2/8] xsk: remove explicit_free parameter from __xsk_rcv() Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 3/8] xsk: fold xp_assign_dev and __xp_assign_dev Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 4/8] xsk: register XDP sockets at bind(), and add new AF_XDP BPF helper Björn Töpel
2021-01-20 8:25 ` kernel test robot
2021-01-20 8:41 ` Björn Töpel
2021-01-20 8:50 ` kernel test robot
2021-01-20 12:50 ` Toke Høiland-Jørgensen
2021-01-20 13:25 ` Björn Töpel
2021-01-20 14:54 ` Toke Høiland-Jørgensen
2021-01-20 15:18 ` Björn Töpel [this message]
2021-01-20 17:29 ` Toke Høiland-Jørgensen
2021-01-20 18:22 ` Björn Töpel
2021-01-20 20:26 ` Toke Høiland-Jørgensen
2021-01-20 21:15 ` Alexei Starovoitov
2021-01-21 8:18 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 5/8] libbpf, xsk: select AF_XDP BPF program based on kernel version Björn Töpel
2021-01-20 12:52 ` Toke Høiland-Jørgensen
2021-01-20 13:25 ` Björn Töpel
2021-01-20 14:49 ` Björn Töpel
2021-01-20 15:11 ` Toke Høiland-Jørgensen
2021-01-20 15:27 ` Björn Töpel
2021-01-20 17:30 ` Toke Høiland-Jørgensen
2021-01-20 18:25 ` Alexei Starovoitov
2021-01-20 18:30 ` Björn Töpel
2021-01-20 14:56 ` Toke Høiland-Jørgensen
2021-01-19 15:50 ` [PATCH bpf-next v2 6/8] libbpf, xsk: select bpf_redirect_xsk(), if supported Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 7/8] selftest/bpf: add XDP socket tests for bpf_redirect_{xsk, map}() Björn Töpel
2021-01-21 7:39 ` Andrii Nakryiko
2021-01-21 12:31 ` Björn Töpel
2021-01-19 15:50 ` [PATCH bpf-next v2 8/8] selftest/bpf: remove a lot of ifobject casting in xdpxceiver Björn Töpel
2021-01-20 13:15 ` [PATCH bpf-next v2 0/8] Introduce bpf_redirect_xsk() helper Maxim Mikityanskiy
2021-01-20 13:27 ` Björn Töpel
2021-01-20 15:57 ` Jesper Dangaard Brouer
2021-01-20 16:19 ` Maciej Fijalkowski
2021-01-21 17:01 ` Jesper Dangaard Brouer
2021-01-22 8:59 ` Magnus Karlsson
2021-01-22 9:45 ` Maciej Fijalkowski
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