[PATCH 00/33] stm32: enable logging features

[Patrick DELAUNAY]

Hi Simon,

> From: Simon Glass <sjg at chromium.org>
> Sent: lundi 26 octobre 2020 20:23
> 
> Hi Patrick,
> 
> On Thu, 15 Oct 2020 at 09:59, Patrick DELAUNAY <patrick.delaunay at st.com>
> wrote:
> >
> > Hi Simon,
> >
> > > From: Simon Glass <sjg at chromium.org>
> > > Sent: jeudi 15 octobre 2020 17:06
> > >
> > > Hi Patrick,
> > >
> > > On Wed, 14 Oct 2020 at 03:16, Patrick Delaunay
> > > <patrick.delaunay at st.com>
> > > wrote:
> > > >
> > > >
> > > > This patch-set migrates several stm32 drivers to API compatible
> > > > with logging features (use dev_...() or log_...() function) and
> > > > activate the logging features in STM32MP15 boards.
> > > >
> > > > The size of U-Boot increased by 19kB (933026 to 952830 on
> > > > STM32MP157C-EV1 board for basic defconfig) but the boot time don't
> > > > change
> > > drastically.
> > >
> > > >

(...)

> > > > For information even with all trace embbeded in U-Boot but not
> > > > activated, MAX_LOG_LEVEL=8 and LOG_DEFAULT_LEVEL=6
> > > >
> > > > Size increase by 190KB (952830 to 1147918) but boot time is stable
> > > > (1,748s vs 1,696s).
> > >
> > > This seems pretty bad. Is this because of console output, or
> > > something else? I understand the size increase, but not the boot time
> increase.
> >
> > For this last point I just execute STM32MP157C-EV1 boot with a patch
> > in configs/stm32mp15_basic_defconfig
> >
> > +CONFIG_LOGLEVEL=8
> > +CONFIG_LOG_MAX_LEVEL=8
> > +CONFIG_LOG_DEFAULT_LEVEL=6
> > +CONFIG_LOGF_FILE=y
> > +CONFIG_LOGF_LINE=y
> > +CONFIG_LOGF_FUNC=y
> >
> > And execute "bootstage report" after the second boot (the first boot
> > is pertubated by env save)
> >
> > I think the delta is linked to
> > 1/ size of U-Boot (SPL spent more time to load U-Boot)
> >     end of SPL 987,579  => 996,117
> 
> OK.
> 
> >
> > 2/ time to check for each debug trace: because I increase the log level
> >    (gd->default_log_level = 6 < MAX_LOG_LEVEL=8)
> 
> This might be the biggest part. If you look at _log() it always does the vsprintf()
> even if in fact log_dispatch() does not dispatch it to anything.

Yes, log_dispatch / log_passes_filter are called after vsnprintf

> I suspect that could be refactored to move the checking to a separate function,
> and then call it before doing the expensive vsprintf().

Or save va_list, fmt in log_rec and call vsnprintf allow when needed in log_dispatch, just before emit

> >
> > 3/ treatment added in log_console_emit (some printf) and
> >     log_dispatch (processing_msg / gd->loghead)
> 
> Likely this is fast.
> 
> >
> > 4/ lower cache performancy as trace code are pesent in memory even
> >     they are not used
> >
> > Can I do some check/experimentation on my side ?
> 
> Yes, if you can use the bootstage_start() and bootstage_accum() within the _log()
> function to measure the total time take in the run.

Ok, I add it in my TODO list

> Regards,
> Simon

Regards

Patrick