linux-kernel - Re: [PATCH v3] power: new trace event to print device suspend and resume time

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Date:	Thu, 18 Jul 2013 10:21:49 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Shuah Khan <shuah.kh@...sung.com>
Cc:	"len.brown@...el.com" <len.brown@...el.com>,
	"pavel@....cz" <pavel@....cz>, "rjw@...k.pl" <rjw@...k.pl>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"fweisbec@...il.com" <fweisbec@...il.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"paul.gortmaker@...driver.com" <paul.gortmaker@...driver.com>,
	"joe@...ches.com" <joe@...ches.com>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"shuahkhan@...il.com" <shuahkhan@...il.com>
Subject: Re: [PATCH v3] power: new trace event to print device suspend and
 resume time

On Thu, 2013-07-18 at 14:00 +0000, Shuah Khan wrote:

> >
> > Don't you want to convert the ops_time on display? You can have:
> >
> > 	TP_printk("%s %s parent=%s state=%s ops=%snsecs=%lld err=%d",
> > 		__get_str(driver), __get_str(device), __get_str(parent),
> > 		__get_str(pm_event_str), __get_str(pm_ops),
> > 		ktime_to_ns(__entry->ops_time), __entry->error)
> >
> >
> > -- Steve
> 
> I decided to pass in the converted value to the tracepoint. Please see 
> the drivers/base/power/main.c call to trace_device_pm_report_time()

But why? You are still doing the calculation in the fast path. The
TP_printk() is in the slow path. Why add overhead to the execution of
the code?

-- Steve

> 
> +
> +	trace_device_pm_report_time(dev_name(dev), dev_driver_string(dev),
> +				dev->parent ? dev_name(dev->parent) : "none",
> +				info ? info : "none ",
> +				(s64) ktime_to_ns(delta), pm_verb(state.event),
> +				error);
> 
> -- Shuah
> 
> Shuah Khan, Linux Kernel Developer - Open Source Group Samsung Research 
> America (Silicon Valley) shuah.kh@...sung.com | (970) 672-0658


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