Re: [PATCH 10] PM: Measure suspend and resume times for individual devices (was: Re: [PATCH 2/6] PM: Asynchronous resume of devices)

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Monday 31 August 2009, Ingo Molnar wrote:
> 
> * Rafael J. Wysocki <rjw@sisk.pl> wrote:
> 
> > On Sunday 30 August 2009, Rafael J. Wysocki wrote:
> > > On Sunday 30 August 2009, Alan Stern wrote:
> > > > On Sat, 29 Aug 2009, Rafael J. Wysocki wrote:
> > > > 
> > > > > I only wanted to say that the advantage is not really that "big". :-)
> > > > > 
> > > > > > I must agree, 14 threads isn't a lot.  But at the moment that number is 
> > > > > > random, not under your control.
> > > > > 
> > > > > It's not directly controlled, but there are some interactions between the
> > > > > async threads, the main threads and the async framework that don't allow this
> > > > > number to grow too much.
> > > > > 
> > > > > IMO it sometimes is better to allow things to work themselves out, as long as
> > > > > they don't explode, than to try to keep everything under strict control.  YMMV.
> > > > 
> > > > For testing purposes it would be nice to have a one-line summary for
> > > > each device containing a thread ID, start timestamp, end timestamp, and
> > > > elapsed time.  With that information you could evaluate the amount of
> > > > parallelism and determine where the bottlenecks are.  It would give a
> > > > much more detailed picture of the entire process than the total time of
> > > > your recent patch 9.
> > > 
> > > Of course it would.  I think I'll implement it.
> > 
> > OK, below is a patch for that.  It only prints the time elapsed, because the
> > timestamps themselves can be obtained from the usual kernel timestamping.
> > 
> > It's on top of all the previous patches.
> > 
> > Thanks,
> > Rafael
> > 
> > ---
> > From: Rafael J. Wysocki <rjw@sisk.pl>
> > Subject: PM: Measure suspend and resume times for individual devices
> > 
> > If verbose PM debugging is enabled, measure and print the time of
> > suspending and resuming of individual devices.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
> > ---
> >  drivers/base/power/main.c |   51 +++++++++++++++++++++++++++++++++++++++++-----
> >  kernel/power/swsusp.c     |    2 -
> >  2 files changed, 47 insertions(+), 6 deletions(-)
> > 
> > Index: linux-2.6/drivers/base/power/main.c
> > ===================================================================
> > --- linux-2.6.orig/drivers/base/power/main.c
> > +++ linux-2.6/drivers/base/power/main.c
> > @@ -442,11 +442,11 @@ static bool pm_op_started(struct device 
> >   */
> >  int pm_time_elapsed(struct timeval *start, struct timeval *stop)
> >  {
> > -	s64 elapsed_centisecs64;
> > +	s64 elapsed_msecs64;
> >  
> > -	elapsed_centisecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
> > -	do_div(elapsed_centisecs64, NSEC_PER_SEC / 100);
> > -	return elapsed_centisecs64;
> > +	elapsed_msecs64 = timeval_to_ns(stop) - timeval_to_ns(start);
> > +	do_div(elapsed_msecs64, NSEC_PER_SEC / 1000);
> > +	return elapsed_msecs64;
> >  }
> >  
> >  static char *pm_verb(int event)
> > @@ -476,7 +476,7 @@ static char *pm_verb(int event)
> >  static void dpm_show_time(struct timeval *start, struct timeval *stop,
> >  			  pm_message_t state, const char *info)
> >  {
> > -	int centisecs = pm_time_elapsed(start, stop);
> > +	int centisecs = pm_time_elapsed(start, stop) / 10;
> >  
> >  	printk(KERN_INFO "PM: %s%s%s of devices complete in %d.%02d seconds\n",
> >  		info ? info : "", info ? " " : "", pm_verb(state.event),
> > @@ -497,6 +497,33 @@ static void pm_dev_err(struct device *de
> >  		kobject_name(&dev->kobj), pm_verb(state.event), info, error);
> >  }
> >  
> > +#ifdef DEBUG
> > +static void device_show_time(struct timeval *start, struct device *dev,
> > +			     pm_message_t state, char *info)
> > +{
> > +	struct timeval stop;
> > +	int msecs;
> > +
> > +	do_gettimeofday(&stop);
> > +	msecs = pm_time_elapsed(start, &stop);
> > +	dev_dbg(dev, "PID %d: %s%s%s complete in %d.%03d seconds\n",
> > +		task_pid_nr(current), info ? info : "", info ? " " : "",
> > +		pm_verb(state.event), msecs / 1000, msecs % 1000);
> > +}
> > +
> > +#define TIMER_DECLARE(timer)	struct timeval timer
> > +#define TIMER_START(timer)	do { \
> > +		do_gettimeofday(&timer); \
> > +	} while (0)
> > +#define TIMER_STOP(timer, dev, state, info)	do { \
> > +		device_show_time(&timer, dev, state, info); \
> > +	} while (0)
> > +#else /* !DEBUG */
> > +#define TIMER_DECLARE(timer)
> > +#define TIMER_START(timer)	do { } while (0)
> > +#define TIMER_STOP(timer, dev, state, info)	do { } while (0)
> > +#endif /* !DEBUG */
> > +
> >  /*------------------------- Resume routines -------------------------*/
> >  
> >  /**
> > @@ -510,7 +537,9 @@ static void pm_dev_err(struct device *de
> >  static int __device_resume_noirq(struct device *dev, pm_message_t state)
> >  {
> >  	int error = 0;
> > +	TIMER_DECLARE(timer);
> >  
> > +	TIMER_START(timer);
> >  	TRACE_DEVICE(dev);
> >  	TRACE_RESUME(0);
> >  
> > @@ -523,6 +552,7 @@ static int __device_resume_noirq(struct 
> >  	wake_up_all(&dev->power.wait_queue);
> >  
> >  	TRACE_RESUME(error);
> > +	TIMER_STOP(timer, dev, state, "EARLY");
> >  	return error;
> 
> Hm, these CPP macros are rather ugly. Why is there a need for the 
> TIMER_DECLARE() wrapper - if a proper inline function is used 
> there's no need for that.

I need a variable to be declared so that I can save the "start" timestamp
in it.  I don't need the variable if DEBUG is unset, though.

How would you do that without using a macro?  Or #ifdef #endif block that
would be uglier IMO (which is why I didn't do that)?

> There's other all-capitals macros in that code implementing code (and not
> constants) - is that really justified/clean?

Do you mean the TRACE_* macros?  Please ask Linus about that, they are from
him. :-)

Thanks,
Rafael