Re: [dpdk-dev] [PATCH 2/2] eal: fix dynamic logs failing to print

[Pavan Nikhilesh Bhagavatula <pbhagavatula@caviumnetworks.com>]

On Mon, Nov 20, 2017 at 10:40:29AM -0800, Ferruh Yigit wrote:
> On 11/17/2017 12:47 AM, Pavan Nikhilesh Bhagavatula wrote:
> > On Thu, Nov 16, 2017 at 11:48:14AM -0800, Ferruh Yigit wrote:
> >> On 11/16/2017 2:31 AM, Pavan Nikhilesh wrote:
> >>> Dynamic logs fail to print if the global log level is less than dynamic
> >>> loglevel. Example if the global log level is set to INFO and dynamic log
> >>> level for a specific module is set to DEBUG then the log fails to print.
> >>
> >> What is the purpose of the global log level value?
> >>
> >
> > As per my understanding, If we want to filter out debug logs from all other
> > modules except a specific module using --log-level="<regex>,<level>" the logs
> > would fail to print if the global log level is lower than the specified level.
>
> Yes.
>
> >
> > If during EAL init we want to filter out all the logs except a certain pmd's
> > log we can specify --log-level="pmd\..*,<level>" without modifying the global
> > log level. Also, this wouldnt break the previous functionality of global log
> > level.
>
> But this overwrites the global and makes it useless.
>
> Lets say global log level is set to "critical" (3), if module set something
> bigger like "info" (7) that will set the limit, so module will be controlling
> and what is the point of having global level?
>
> It can be an option remove global level completely and let modules control what
> to log, but I believe it can be useful to have a global control.
>
>
> What about having a verbose global and limited module log levels:
> global default: debug (8)
> modules default: info (7)
>
> so if you want get verbose log from specific module:
> --log-level="<regex>,8"
>
> for globally less verbose log:
> --log-level=3
>
> But this makes hard to enable verbose log from everything, although not sure how
> practical is this. For this one it can be possible to have a new API to set
> modules other than given one, like:
> --log-level="eal,-4"  --> set level of all modules except "eal" to "error" (4)
>
>
> Also I believe it is possible to remove RTE_LOG_LEVEL config option completely
> since dynamic debug exist now. Previously it was good to have because it was
> used to compile out debug functions in data path, now there is
> "RTE_LOG_DP_LEVEL" for that purpose, so it can be possible to remove
> RTE_LOG_LEVEL and in rte_log_init() set to DEBUG by default if you agree with
> above approach.
>

I do agree with this approach it gives more fluid control over logging.
And for the case where we want to match everything except we could still use
regex example: https://regex101.com/r/vqGiUK/1/

>
>
> And, since you are touching these files :),
> for better regex support, it may be good to have log types hierarchical, like
> "lib.mbuf", "lib.mempool", "lib.eal.malloc", as done in member library but with
> "lib" prefix instead of "librte", if this makes sense and you have time would
> you mind sending a patch for this as well?
>

I will redo the patchset including these :).

>
> Thanks,
> ferruh
>
> >
> >>> Check modules log level before checking the global log level.
> >>>
> >>> Fixes: c1b5fa94a46f ("eal: support dynamic log types")
> >>>
> >>> Signed-off-by: Pavan Nikhilesh <pbhagavatula@caviumnetworks.com>
> >>
> >> <...>
> >>
>