netdev - Re: [RFC PATCH bpf-next] bpf, xdp: per-map bpf_redirect

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Date:   Fri, 29 Jan 2021 19:06:06 +0100
From:   Jesper Dangaard Brouer <jbrouer@...hat.com>
To:     Björn Töpel <bjorn.topel@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Netdev <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Björn Töpel <bjorn.topel@...el.com>,
        "Karlsson, Magnus" <magnus.karlsson@...el.com>,
        "Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Jonathan Lemon <jonathan.lemon@...il.com>, maximmi@...dia.com,
        David Miller <davem@...emloft.net>,
        Jesper Dangaard Brouer <hawk@...nel.org>,
        John Fastabend <john.fastabend@...il.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>
Subject: Re: [RFC PATCH bpf-next] bpf, xdp: per-map bpf_redirect_map
 functions for XDP

On Fri, 29 Jan 2021 16:35:47 +0100
Björn Töpel <bjorn.topel@...il.com> wrote:

> On Fri, 29 Jan 2021 at 16:32, Björn Töpel <bjorn.topel@...il.com> wrote:
> >
> > From: Björn Töpel <bjorn.topel@...el.com>
> >  
> [...]
> >
> > For AF_XDP rxdrop this yields +600Mpps. I'll do CPU/DEVMAP
> > measurements for the patch proper.
> >  
> 
> Kpps, not Mpps. :-P

+600Kpps from 24Mpps to 24.6Mpps I assume.  This corresponds to approx
1 ns ((1/24-1/24.6)*1000 = 1.01626 ns).

This also correlate with saving one function call, which is basically
what the patch does.

Fresh measurement "Intel(R) Xeon(R) CPU E5-1650 v4 @ 3.60GHz" with [1]:
 time_bench: Type:funcion_call_cost Per elem: 3 cycles(tsc) 1.053 ns
 time_bench: Type:func_ptr_call_cost Per elem: 4 cycles(tsc) 1.317 ns

[1] https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/lib/time_bench_sample.c
-- 
Best regards,
  Jesper Dangaard Brouer
  MSc.CS, Principal Kernel Engineer at Red Hat
  LinkedIn: http://www.linkedin.com/in/brouer