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Re: [Minios-devel] [UNIKRAFT PATCH] lib/ukdebug: print DLVL_EXTRA messages only in debug build



Hi,

so after reading your's and Simon's answer, I'm still not quite clear about one thing. Is this planned to be per-subsystem or not? It sounded to me like it's not, and it's governed by a global define UK_DEBUG for all subsystems.

Or is it really strictly just for temporary debugging, i.e., a patch applied to staging/master should never have any uk_printd() calls in it?

Cheers,
Florian

On 08/01/2018 12:03 PM, Yuri Volchkov wrote:
Hi,

I kinda like approaches like the linux kernel has, which allows you to
set debug output per subsystem level (which I guess in our case would
be libraries)
In fact the proposal was to do it similar to linux kernel scheme. Here
is a sentence from
https://www.kernel.org/doc/html/v4.10/process/coding-style.html

  "While the other pr_XXX() functions print unconditionally, pr_debug()
   does not; it is compiled out by default, unless either DEBUG is
   defined or CONFIG_DYNAMIC_DEBUG is set."

Matching it to what Simon wrote:
1) uk_printk is equivalent to linux's printk with levels up to KERN_INFO

2) uk_printd is equivalent to linux's pr_debug(). However, in linux just
    defining "DEBUG" for a file or subsystem is not enough, you also need
    to change the printk level to KERN_DEBUG (e.g. echo 7 >
    /proc/sys/kernel/printk). The same happens in current patch I have
    sent, but the idea is to make debug output independent from the
    current selected level in the future.


because global log levels of high verbosity can end up drowning you in
messages.
Right, non-debug output should be readable even at maximum verbosity
level. If a print spits to many messages it either should be pr_debug
(or whatever we name it), or, it should be rate limited.

However, I'm aware that's a bit of a larger redesign, so I'm not sure we
want to go for it at the moment.
This is dynamic print. We will get there eventually. This patch is a
first baby step towards it.

-Yuri.

Florian Schmidt <florian@xxxxxxxxx> writes:

Hi everyone,

On 07/31/2018 03:05 PM, Simon Kuenzer wrote:
Give me a +1/0/-1.

I'm a 0 on this one.

I agree that it's (slightly) less confusing than the current situation.
Then again, I kinda like approaches like the linux kernel has, which
allows you to set debug output per subsystem level (which I guess in our
case would be libraries) because global log levels of high verbosity can
end up drowning you in messages.

However, I'm aware that's a bit of a larger redesign, so I'm not sure we
want to go for it at the moment.

Cheers, Florian

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