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

Ingo Molnar
2009-08-31T07:26:58Z

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

Ingo