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: <d4f761c3-d133-4f89-44c2-a96c7f917571@netronome.com>
Date:   Tue, 30 Apr 2019 10:34:20 +0100
From:   Quentin Monnet <quentin.monnet@...ronome.com>
To:     Y Song <ys114321@...il.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

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.

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>