Re: gdmgreeter CPU usage

["Padraig O'Briain" <Padraig Obriain Sun COM>]

I have got my Performance Analyzer from Sun Studio 11 working on
gdmgreeter and I see that 50% of the CPU used by gdmgreeter is used by
FcFontSort.

FcFontSort is called 12 times by gdmgreeter. Each time it is called the
top of the function stack is the same:

libfontconfig.so.1.0.4`FcFontSort
libpangoft2-1.0.so.0.1101.0`pango_fc_font_map_get_patterns+0x1f4
libpangoft2-1.0.so.0.1101.0`pango_fc_font_map_load_fontset+0x39
libpango-1.0.so.0.1101.0`pango_font_map_load_fontset+0x3c

I see that pango_font_map_load_font is called about 200 times; 12 of
these calls are for description "Bitstream Vera Sans" and the rest are
for "Sans". The cost of the calls for "Sans" are negligible excapt for
the first one.

The calls for "Bitstream Vera Sans" are the calls which call FcFontSort
and cost about 30 ms each.

I have not yet figured out how to determine whether the values returned
are the same.

Padraig



On Wed, 2006-01-11 at 12:44 -0600, Federico Mena Quintero wrote:
> On Wed, 2006-01-11 at 09:05 +0000, Padraig O'Briain wrote:
> > FcFontSort is called 12 times during gdmgreeter startup, with a total
> > cost of 205 ms of CPU.
> > 
> > As this occurs during the boot phase I suspect that the elapsed time is
> > even longer.
> > 
> > I have bootchart that show that gdmgreeter takes about 5 seconds to
> > startup when booting. About 860 ms of that is CPU time.
> 
> Ah.  Now we are getting somewhere :)
> 
> I haven't looked at the dtrace log you posted - I assume it has a
> breakdown of the user time for various parts of gdm?
> 
> Even though FcFontSort is only 4% of gdm's startup time, it will affect
> all GNOME apps at startup, since each of them has to invoke it several
> times.
> 
> - Do we really need to call it 12 times?  Just how many different font
> descriptions does gdm use?
> 
> - Given the same parameters, does the function always return the same
> value?  I don't want to put in a cache prematurely, but this would be
> useful to know.
> 
> - Can we get a little program that runs FcFontSort in a loop so that we
> can profile it?
> 
>   Federico
> 
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