Re: [GIT PULL] PM updates for 2.6.33

Ingo Molnar
2009-12-06T08:39:41Z

* Arjan van de Ven <arjan@infradead.org> wrote:

> On Sun, 6 Dec 2009 02:26:06 +0100
> "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
>
> > On Sunday 06 December 2009, Arjan van de Ven wrote:
> > > On Sun, 6 Dec 2009 00:55:36 +0100
> > > "Rafael J. Wysocki" <rjw@sisk.pl> wrote:
> > >
> > > >
> > > > Disk spinup/spindown takes time, but also some ACPI devices resume
> > > > slowly, serio devices do that too and there are surprisingly many
> > > > drivers that wait (using msleep() during suspend and resume).
> > > > Apart from this, every PCI device going from D0 to D3 during
> > > > suspend and from D3 to D0 during resume requires us to sleep for
> > > > 10 ms (the sleeping is done by the PCI core, so the drivers don't
> > > > even realize its there).
> > >
> > > maybe a good step is to make a scripts/bootgraph.pl equivalent for
> > > suspend/resume (or make a debug mode that outputs in a compatible
> > > format so that the script can be used as is.. I don't mind either
> > > way, and consider this my offer to help with such a script as long
> > > as there's sufficient logging in dmesg ;-)
> >
> > OK, so what kind of logging is needed?
>
> basically the equivalent of the two initcall_debug paths in
>
> init/main.c:do_one_initcall()
>
> which prints a start time and an end time (and a pid) for each init
> function; if we have the same for suspend calls (and resume)... we can
> make the tool graph it.
>
> Would be nice to get markers for start and end of the whole suspend
> sequence as well as for the resume sequence; those make it easier to
> know when the end is (so that the axis can be drawn etc)
>
> shouldn't be too hard to implement...

I think an even better option would be to extend 'perf timechart' to be
suspend/resume aware: add a few tracepoint events and teach 'perf
timechart' to draw them. (We should be able to do perf timechart record
across suspend/resume cycles just fine.)

( Doing that would also improve the tracing facilities within
suspend/resume quite significantly. It wouldnt just be a
single-purpose thing for graphing, but perf trace and perf stat would
work equally well. )

Thanks,

Ingo