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


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