Messages in this thread | | | Subject | Re: [PATCH v2] power: new trace event to print device suspend and resume time | From | Joe Perches <> | Date | Wed, 17 Jul 2013 09:41:08 -0700 |
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On Wed, 2013-07-17 at 16:30 +0000, Shuah Khan wrote: > On 07/17/2013 10:09 AM, Joe Perches wrote: > > On Wed, 2013-07-17 at 09:57 -0600, Shuah Khan wrote: > >> A new trace event is added to pm events to print time it takes to suspend and > >> resume a device. It generates trace message that includes device, driver, > >> parent information in addition to the type of pm ops invoked as well as the > >> pm event and error status from the pm ops. Example trace below: > >> > >> bash-2484 [001] .... 907.330148: device_pm_report_time: backlight acpi_video0 parent=0000:00:02.0 state=freeze ops=class usecs=0 err=0 > >> > >> bash-2484 [001] .... 909.906743: device_pm_report_time: backlight acpi_video0 parent=0000:00:02.0 state=restore ops=class usecs=0 err=0 [] > > Given the data is in nsecs, why use usecs for the time? > > I think full resolution would be better. > > My intent to was to match the time units to the original pm_print_times.
I don't think that maintaining consistency is useful in a new facility when you lose precision.
Also the accuracy is suspect as it's calculated with >>10 rather than an actual divide by 1000.
> Rafael! Do you have any preference as to usecs vs. nsecs?
> > Why are there two spaces after "ops=class"? One would be more normal.
> This one is tough. The ops string that gets generated in conditionals in > __device_suspend() and device_resume() routines, has an extra space at > the end. I am not sure why that was done and the subsequent pr_* that > print that string also depend on that extra space at the end. I don't > have an easy way to fix it without changing lots of code where this > string is generated.
I think the easiest way to "fix" it is to change the TP_printk format to:
TP_printk("%s %s parent=%s state=%s ops=%susecs=%lld err=%d",
> Hence, I chose to leave the extra space in. I also > didn't want to propagate that assumption that there is an extra space > into this new tracepoint.
It's a big deal, it just seemed untidy.
There are a couple of places in drivers/base/power/main.c where info is set to NULL. I didn't look hard to see if any of those are propagated through to this point, but there are uses of 'info ?: ""' for some of the logging messages. That _might_ an issue.
It looks like all the other logging message uses of info have "%s%s" so that proper word spacing is done when info is "" or NULL.
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