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From: "Toke Høiland-Jørgensen" <toke@redhat.com>
To: "Björn Töpel" <bjorn.topel@gmail.com>,
	netdev@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net
Cc: "Björn Töpel" <bjorn.topel@intel.com>,
	bpf@vger.kernel.org, magnus.karlsson@gmail.com,
	magnus.karlsson@intel.com, jonathan.lemon@gmail.com,
	ecree@solarflare.com, thoiland@redhat.com, brouer@redhat.com,
	andrii.nakryiko@gmail.com
Subject: Re: [PATCH bpf-next v4 2/6] bpf: introduce BPF dispatcher
Date: Wed, 11 Dec 2019 14:26:38 +0100	[thread overview]
Message-ID: <87wob3f0xd.fsf@toke.dk> (raw)
In-Reply-To: <20191211123017.13212-3-bjorn.topel@gmail.com>

[...]
> +/* The BPF dispatcher is a multiway branch code generator. The
> + * dispatcher is a mechanism to avoid the performance penalty of an
> + * indirect call, which is expensive when retpolines are enabled. A
> + * dispatch client registers a BPF program into the dispatcher, and if
> + * there is available room in the dispatcher a direct call to the BPF
> + * program will be generated. All calls to the BPF programs called via
> + * the dispatcher will then be a direct call, instead of an
> + * indirect. The dispatcher hijacks a trampoline function it via the
> + * __fentry__ of the trampoline. The trampoline function has the
> + * following signature:
> + *
> + * unsigned int trampoline(const void *xdp_ctx,
> + *                         const struct bpf_insn *insnsi,
> + *                         unsigned int (*bpf_func)(const void *,
> + *                                                  const struct bpf_insn *));
> + */

Nit: s/xdp_ctx/ctx/

-Toke


  reply	other threads:[~2019-12-11 13:26 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-11 12:30 [PATCH bpf-next v4 0/6] Introduce the BPF dispatcher Björn Töpel
2019-12-11 12:30 ` [PATCH bpf-next v4 1/6] bpf: move trampoline JIT image allocation to a function Björn Töpel
2019-12-11 12:30 ` [PATCH bpf-next v4 2/6] bpf: introduce BPF dispatcher Björn Töpel
2019-12-11 13:26   ` Toke Høiland-Jørgensen [this message]
2019-12-13  8:23     ` Björn Töpel
2019-12-13  5:30   ` Alexei Starovoitov
2019-12-13  7:51     ` Björn Töpel
2019-12-13 15:04       ` Alexei Starovoitov
2019-12-13 15:49         ` Björn Töpel
2019-12-13 15:51           ` Alexei Starovoitov
2019-12-13 15:59             ` Björn Töpel
2019-12-13 16:03               ` Alexei Starovoitov
2019-12-13 16:09                 ` Björn Töpel
2019-12-13 17:18                   ` Alexei Starovoitov
2022-08-15 14:13   ` Steven Rostedt
2022-08-15 14:31     ` Alexei Starovoitov
2022-08-15 14:56       ` Peter Zijlstra
2022-08-15 15:16       ` Steven Rostedt
2022-08-15 15:19         ` Alexei Starovoitov
2022-08-15 15:21         ` Steven Rostedt
2022-08-15 15:39         ` Steven Rostedt
2019-12-11 12:30 ` [PATCH bpf-next v4 3/6] bpf, xdp: start using the BPF dispatcher for XDP Björn Töpel
2019-12-11 12:30 ` [PATCH bpf-next v4 4/6] bpf: start using the BPF dispatcher in BPF_TEST_RUN Björn Töpel
2019-12-11 12:30 ` [PATCH bpf-next v4 5/6] selftests: bpf: add xdp_perf test Björn Töpel
2019-12-11 12:30 ` [PATCH bpf-next v4 6/6] bpf, x86: align dispatcher branch targets to 16B Björn Töpel
2019-12-11 12:33 ` [PATCH bpf-next v4 0/6] Introduce the BPF dispatcher Björn Töpel

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