Re: [dpdk-dev] [PATCH] log: do not drop debug logs at compile time

[Olivier Matz <olivier.matz@6wind.com>]

On 10/03/2016 05:27 PM, Wiles, Keith wrote:
> 
> Regards,
> Keith
> 
>> On Oct 3, 2016, at 10:02 AM, Olivier Matz <olivier.matz@6wind.com> wrote:
>>
>> Hi Keith,
>>
>> On 09/30/2016 05:48 PM, Wiles, Keith wrote:
>>>> On Sep 30, 2016, at 4:33 AM, Thomas Monjalon <thomas.monjalon@6wind.com> wrote:
>>>>
>>>> 2016-09-16 09:43, Olivier Matz:
>>>>> Today, all logs whose level is lower than INFO are dropped at
>>>>> compile-time. This prevents from enabling debug logs at runtime using
>>>>> --log-level=8.
>>>>>
>>>>> The rationale was to remove debug logs from the data path at
>>>>> compile-time, avoiding a test at run-time.
>>>>>
>>>>> This patch changes the behavior of RTE_LOG() to avoid the compile-time
>>>>> optimization, and introduces the RTE_LOG_DP() macro that has the same
>>>>> behavior than the previous RTE_LOG(), for the rare cases where debug
>>>>> logs are in the data path.
>>>>>
>>>>> So it is now possible to enable debug logs at run-time by just
>>>>> specifying --log-level=8. Some drivers still have special compile-time
>>>>> options to enable more debug log. Maintainers may consider to
>>>>> remove/reduce them.
>>>>>
>>>>> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
>>>>
>>>> I think it is a good change.
>>>> However I'm not sure we should take it for 16.11 as it was sent late and
>>>> there is no review comment.
>>>> It is neither really a fix nor really a feature.
>>>> If there are some +1, and no opinions against, it will go in 16.11.
>>>> Note that some drivers would need some changes to fully benefit of
>>>> debug logs enabled at run-time.
>>>
>>> Would this be easier to add a new LOG level instead say DEBUG_DATAPATH and then change the RTE_LOG to exclude the new log level?
>>>
>>>
>>
>> The log levels are quite standard, I don't feel it would be very clear
>> to have a new level for that. It would also prevent to have different
>> log level inside data path.
> 
> I am not following you here. Having one more log level for DEBUG in the data path is not a big change and you can still have any other log level in the data or anyplace else for that matter.

Adding a new log level is not a big change, you are right.
But to me it looks confusing to have DEBUG, INFO, ..., WARNING, ERROR,
plus a DEBUG_DATAPATH. For instance, how do you compare levels? Or if
your log stream forwards logs to syslog, you cannot do a 1:1 mapping
with standard syslog levels.

What makes you feel it's easier to add a log level instead of adding a
new RTE_LOG_DP() function?


Regards,
Olivier