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Message-ID: <CAJ+HfNjZnxrgYtTzbqj2VOP+5A81UW-7OKoReT0dMVBT0fQ1pg@mail.gmail.com> Date: Mon, 9 Dec 2019 18:42:22 +0100 From: Björn Töpel <bjorn.topel@...il.com> To: Toke Høiland-Jørgensen <toke@...hat.com> Cc: Netdev <netdev@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, bpf <bpf@...r.kernel.org>, Magnus Karlsson <magnus.karlsson@...il.com>, "Karlsson, Magnus" <magnus.karlsson@...el.com>, Jonathan Lemon <jonathan.lemon@...il.com>, Edward Cree <ecree@...arflare.com>, Toke Høiland-Jørgensen <thoiland@...hat.com>, Andrii Nakryiko <andrii.nakryiko@...il.com> Subject: Re: [PATCH bpf-next v3 0/6] Introduce the BPF dispatcher On Mon, 9 Dec 2019 at 16:00, Toke Høiland-Jørgensen <toke@...hat.com> wrote: > > Björn Töpel <bjorn.topel@...il.com> writes: > [...] > > I like the new version where it's integrated into bpf_prog_run_xdp(); > nice! :) > Yes, me too! Nice suggestion! > > The XDP dispatcher is always enabled, if available, because it helps > > even when retpolines are disabled. Please refer to the "Performance" > > section below. > > Looking at those numbers, I think I would moderate "helps" to "doesn't > hurt" - a difference of less than 1ns is basically in the noise. > > You mentioned in the earlier version that this would impact the time it > takes to attach an XDP program. Got any numbers for this? > Ah, no, I forgot to measure that. I'll get back with that. So, when a new program is entered or removed from dispatcher, it needs to be re-jited, but more importantly -- a text poke is needed. I don't know if this is a concern or not, but let's measure it. Björn > -Toke >
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