Re: [PATCH v5] printk: Add pr_info_show_time

Luis R. Rodriguez
2017-07-21T02:01:02Z

On Thu, Jul 20, 2017 at 11:24:22AM -0700, Mark Salyzyn wrote:
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index 98fe715522e8..0d63c3fb4e24 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -30,6 +30,58 @@ config CONSOLE_LOGLEVEL_DEFAULT
> usage in the kernel. That is controlled by the MESSAGE_LOGLEVEL_DEFAULT
> option.
>
> +# set if time is being printed in pr_info_show_time()
> +config PR_INFO_SHOW_TIME
> + bool
> +
> +choice
> + prompt "pr_info_show_time() alternate time message prefix"
> + help
> + Activate alternate time prefix in pr_info_show_time
> +
> + The primary use of the instrumentation is to aid field
> + analysis of Battery and Power usage. The instrumentation
> + may also help triage and synchronize kernel logs and user
> + space activity logs at key displacements.
> + config PR_INFO_SHOW_TIME_MONOTONIC
> + bool "monotonic"
> + help
> + Deactivate alternate time prefix in pr_info_show_time.
> + Doing so because monotonic time is part of the normal
> + printk time logging.
> +
> + Print only the supplied message in pr_info_show_time,
> + indistinguishable from pr_info.
> + config PR_INFO_SHOW_TIME_REALTIME
> + bool "realtime"
> + select PR_INFO_SHOW_TIME
> + help
> + Activate alternate time prefix in pr_info_show_time
> +
> + The primary use of the instrumentation is to aid field
> + analysis of Battery and Power usage. The instrumentation
> + may also help triage and synchronize kernel logs and user
> + space activity logs at key displacements. For instance
> + CLOCK_MONOTONIC stops while suspended, while CLOCK_REALTIME
> + continues, and the timestamps help re-orient post-analysis.
> +
> + Prefix realtime [<epoch>.<ns>U] timestamp in pr_info_show_time
> + config PR_INFO_SHOW_TIME_BOOTTIME
> + bool "boottime"
> + select PR_INFO_SHOW_TIME
> + help
> + Activate alternate time prefix in pr_info_show_time
> +
> + The primary use of the instrumentation is to aid field
> + analysis of Battery and Power usage. The instrumentation
> + may also help triage and synchronize kernel logs and user
> + space activity logs at key displacements. For instance
> + CLOCK_MONOTONIC stops while suspended, while CLOCK_BOOTTIME
> + continues, and the timestamps help re-orient post-analysis.
> +
> + Prefix boottime [<epoch>.<ns>B] timestamp in pr_info_show_time
> +endchoice

There is no depends magic anywhere here, so none of this actually has complex
dependencies, this is just boot time preference setup, and for that I think a
boot param and sysctl value could easily not only enable the same but *also*
enable run time ability to swap between these. Even for the branch performance
consideration can't jump labels be used to address that if there is a concern
for that?

I think that would also make the code easier to read and remove all this kconfig
extra stuff. Then its just a run time thing.

Also, should there be no checks for time being available and ready before this
is used?

Luis