Re: [Powertop] Some more NaNs in report when CONFIG_TRACING is not enabled

[Chris Ferron <chris.e.ferron at linux.intel.com>]

[-- Attachment #1: Type: text/plain, Size: 1284 bytes --]

On 08/17/2012 04:51 AM, Igor Zhbanov wrote:
> Hello!
>
> When you run the PowerTOP on the kernel with CONFIG_TRACING disabled,
> you will get several NaNs (not a number) in the report. PowerTOP 
> doesn't correctly
> handle the situation when /sys/kernel/debug is present but 
> /sys/kernel/debug/tracing is not.
>
> So the PowerTOP will be unable to get information about trace events. 
> And instead of
> arguing about that or skipping some tests, it will run and produce 
> wrong reports.
>
> Since there will be no trace events captured, the measurement_time 
> variable
> in src/process/do_process.c will remain zero. So the functions like 
> total_wakeups(),
> total_gpu_ops(), total_disk_hits(), etc. will happily divide total by 
> zero.
>
> Yes, I know that it is not very useful to run the PowerTOP with 
> tracing disabled (although
> the PowerTOP can still report information about devices), but I 
> suppose that the PowerTOP
> should check whether /sys/kernel/debug/tracing presents and say 
> something if not.
>
> And as I see the PowerTOP almost never check the result of file 
> opening functions.
> If it cannot open a file, the PowerTOP just silently skip it.
>
> Thank you.
>
Great, thanks, I will start look at this.
-Chris