netdev - Re: [PATCH net-next 7/7] samples/bpf: xdp_monitor tool based on tracepoints

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Date:   Tue, 29 Aug 2017 10:05:52 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jesper Dangaard Brouer <brouer@...hat.com>
Cc:     netdev@...r.kernel.org, John Fastabend <john.fastabend@...il.com>
Subject: Re: [PATCH net-next 7/7] samples/bpf: xdp_monitor tool based on
 tracepoints

On Tue, Aug 29, 2017 at 04:38:11PM +0200, Jesper Dangaard Brouer wrote:
> This tool xdp_monitor demonstrate how to use the different xdp_redirect
> tracepoints xdp_redirect{,_map}{,_err} from a BPF program.
> 
> The default mode is to only monitor the error counters, to avoid
> affecting the per packet performance. Tracepoints comes with a base
> overhead of 25 nanosec for an attached bpf_prog, and 48 nanosec for
> using a full perf record (with non-matching filter).  Thus, default
> loading the --stats mode could affect the maximum performance.
> 
> This version of the tool is very simple and count all types of errors
> as one.  It will be natural to extend this later with the different
> types of errors that can occur, which should help users quickly
> identify common mistakes.
> 
> Because the TP_STRUCT was kept in sync all the tracepoints loads the
> same BPF code.  It would also be natural to extend the map version to
> demonstrate how the map information could be used.
> 
> Signed-off-by: Jesper Dangaard Brouer <brouer@...hat.com>

Nice. Did you consider using libbbpf (instead of old bpf_load.c hack)
and make full standalone tool out of it? Looks very useful.
Acked-by: Alexei Starovoitov <ast@...nel.org>