netdev - Re: [PATCH bpf-next 1/6] tools: bpftool: add --log-libbpf option to get debug info from libbpf

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Message-ID: <CAH3MdRXFBsBdrmTc36yBs0Y0wcz4tOk-cBY4q6_s9bmtdnctyA@mail.gmail.com>
Date:   Tue, 30 Apr 2019 08:31:53 -0700
From:   Y Song <ys114321@...il.com>
To:     Quentin Monnet <quentin.monnet@...ronome.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        bpf <bpf@...r.kernel.org>, netdev <netdev@...r.kernel.org>,
        oss-drivers@...ronome.com
Subject: Re: [PATCH bpf-next 1/6] tools: bpftool: add --log-libbpf option to
 get debug info from libbpf

On Tue, Apr 30, 2019 at 2:34 AM Quentin Monnet
<quentin.monnet@...ronome.com> wrote:
>
> Hi Yonghong,
>
> 2019-04-29 16:32 UTC-0700 ~ Y Song <ys114321@...il.com>
> > On Mon, Apr 29, 2019 at 2:53 AM Quentin Monnet
> > <quentin.monnet@...ronome.com> wrote:
> >>
> >> libbpf has three levels of priority for output: warn, info, debug. By
> >> default, debug output is not printed to stderr.
> >>
> >> Add a new "--log-libbpf LOG_LEVEL" option to bpftool to provide more
> >> flexibility on the log level for libbpf. LOG_LEVEL is a comma-separated
> >> list of levels of log to print ("warn", "info", "debug"). The value
> >> corresponding to the default behaviour would be "warn,info".
> >
> > Do you think option like "warn,debug" will be useful for bpftool users?
> > Maybe at bpftool level, we could allow user only to supply minimum level
> > for log output, e.g., "info" will output "warn,info"?
> I've been pondering this, too. Since we allow to combine all levels for
> the verifier logs it feels a bit odd to be less flexible for libbpf. And
> we could imagine a user who wants verifier logs (so libbpf "debug") but
> prefers to limit libbpf output (so no "info")... Although I admit this
> might be a bit far-fetched.
>
> I can resend a version with the option taking only the minimal log
> level, as you describe, if you think this is best.

Thanks, I think providing a single minimum level for output probably
better.

Yonghong

>
> Quentin
>
> >
> >>
> >> Internally, we simply use the function provided by libbpf to replace the
> >> default printing function by one that prints logs for all required
> >> levels.
> >>
> >> Signed-off-by: Quentin Monnet <quentin.monnet@...ronome.com>
> >> Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>