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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
	ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
Cc: "Björn Töpel" <bjorn.topel@intel.com>,
	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
Subject: Re: [RFC PATCH bpf-next] bpf, xdp: per-map bpf_redirect_map functions for XDP
Date: Fri, 29 Jan 2021 17:45:27 +0100	[thread overview]
Message-ID: <87im7fy9nc.fsf@toke.dk> (raw)
In-Reply-To: <20210129153215.190888-1-bjorn.topel@gmail.com>

Björn Töpel <bjorn.topel@gmail.com> writes:

> From: Björn Töpel <bjorn.topel@intel.com>
> Currently the bpf_redirect_map() implementation dispatches to the
> correct map-lookup function via a switch-statement. To avoid the
> dispatching, this change adds one bpf_redirect_map() implementation per
> map. Correct function is automatically selected by the BPF verifier.
> Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
> ---
> Hi XDP-folks!
> This is another take on my bpf_redirect_xsk() patch [1]. I figured I
> send it as an RFC for some early input. My plan is to include it as
> part of the xdp_do_redirect() optimization of [1].

Assuming the maintainers are OK with the special-casing in the verifier,
this looks like a neat way to avoid the runtime overhead to me. The
macro hackery is not the prettiest; I wonder if the same effect could be
achieved by using inline functions? If not, at least a comment
explaining the reasoning (and that the verifier will substitute the
right function) might be nice? Mostly in relation to this bit:

>  static const struct bpf_func_proto bpf_xdp_redirect_map_proto = {
> -	.func           = bpf_xdp_redirect_map,
> +	.func           = bpf_xdp_redirect_devmap,

Ah, if only we were writing the kernel in a language with proper macro
support... One can dream! :)

>> For AF_XDP rxdrop this yields +600Mpps. I'll do CPU/DEVMAP
>> measurements for the patch proper.
> Kpps, not Mpps. :-P

Aww, too bad ;)
Still, nice!


       reply	other threads:[~2021-01-29 16:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <20210129153215.190888-1-bjorn.topel@gmail.com>
2021-01-29 16:45 ` Toke Høiland-Jørgensen [this message]
2021-02-01  6:27   ` Björn Töpel
2021-02-01  9:31     ` Jesper Dangaard Brouer
2021-02-01  9:49       ` Björn Töpel
     [not found] ` <CAJ+HfNiFtRd-KKMB1t3Mi3MZ=C+u5TTM5YFnzJFfR4Ruzc7c9Q@mail.gmail.com>
2021-01-29 18:06   ` Jesper Dangaard Brouer

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