Re: Performance data for nautilus

[Alexander Larsson <alexl redhat com>]

On Sat, 19 Oct 2002, Tim Janik wrote:

> On Fri, 18 Oct 2002, Alexander Larsson wrote:
> 
> > On Wed, 16 Oct 2002, Anand Subramanian wrote:
> 
> > > On a sequel to the gedit performance data, we are attaching the
> > > performance report for nautilus.
> 
> > Very interesting. As usual it shows up GObject at its worst.
> 
> i don't think this is a particularly fair comment to make for the
> performance data you posted.

I'm just frustrated with gtype.c always showing up at multiple positions 
in the top 5 functions when profiling Nautilus.

> >   *  Distribution to Callers:
> >   *    203845 times (18.63% of f+d time) g_object_ref
> >   *    210290 times (19.22% of f+d time) g_object_unref
> >   * *********************************************************
> >
> > It seems a full 2.4% of the nautilus execution time is spent making sure
> > that what you pass to g_object_ref/unref() is actually GObjects.
> > I'm not sure it's really worth that. Maybe we should change G_IS_OBJECT to
> > g_type_fundamental (((GTypeInstance *)(instance))->g_class->g_type) ==
> > G_TYPE_OBJECT.
> 
> boom, segfault. in case instance==NULL, or instance->g_class == NULL. two
> frequent cases intended to be caught by the *_IS_*() macros. so if at all,
> you better make this:
>   g_return_if_fail (g_type_check_instance_is_fundamental (object, G_TYPE_OBJECT));
> with, roughly:
> 
> gboolean
> g_type_check_instance_is_fundamental (GTypeInstance *instance,
>                                       GType          ftype)
> {
>   TypeNode *node;
>   if (!instance || !instance->g_class)
>     return FALSE;
>   node = lookup_type_node_I (instance->g_class->g_type);
>   return node && node->is_instantiatable && NODE_FUNDAMENTAL_TYPE (node) == ftype;
> }
> 
> which isn't radically faster than g_type_check_instance_is_a() for the
> non-interface case, which only adds:
> 
>   TypeNode *iface_node = lookup_type_node_I (ftype);
>   if (iface_node->n_supers <= node->n_supers &&
>       node->supers[node->n_supers - iface_node->n_supers] == NODE_TYPE (iface_node))
>     return TRUE;
> 
> so i guess you might be able to save maybe 10% or 15% of
> g_type_check_instance_is_a() call time, only for the G_TYPE_OBJECT
> case though.

It would still help some, at no loss in efficiency. I'm with owen on 
the instance->g_class == NULL check though.
 
> > Or maybe we should just totally dump the typecheck?
> 
> in general, or just for g_object_(un)ref()?
> exactly because ref/unref are called so frequently, they are likely
> to catch broken objects, which is why i wouldn't advocate removing
> them from these two functions.

Just for g_object_(un)ref. Yes, they are called so frequently, which can 
also be argued is a good reason to avoid doing the checks in them. Object 
are seldom just reffed/unreffed, and any other operation on the object 
would cause the check too. I'm not seriously proposing this though, I've 
seen far to much broken code that spew g_warnings.
 
> >   * *********************************************************
> >   *  Function:                      g_type_check_instance_cast
> >   *  Called:                           915215 times
> >   *  Function time:                 120808380 cycles ( 2.23% of .root.)
> >   *  Function+descendants time:     303024736 cycles ( 5.61% of .root.)
> >   *  Distribution to Callers:
> >   *     20905 times ( 2.28% of f+d time) gdk_event_translate
> >   *     38552 times ( 4.20% of f+d time) pango_fontset_simple_get_font
> >   *     93995 times (10.24% of f+d time) gtk_widget_event_internal
> >   *     62804 times ( 6.98% of f+d time) gtk_signal_emit
> >   * *********************************************************
> >
> > These are small fish compared to the ref/unrefs, but they still stick out
> > a bit to much.
> 
> eek. this is a different profile run, and *where* do ref/unref show up
> here?

There were two profile runs, all the interesting data is in the file I
attached, and full annotated gtype.c is in the wipro report:
http://perfgnome.0catch.com/nautilus/copypaste/gtype.as.tar.gz
http://perfgnome.0catch.com/nautilus/newwin/gtype.as.tar.gz

-- 
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 Alexander Larsson                                            Red Hat, Inc 
                   alexl redhat com    alla lysator liu se 
He's a leather-clad arachnophobic vampire hunter who dotes on his loving old 
ma. She's a mistrustful red-headed research scientist who inherited a spooky 
stately manor from her late maiden aunt. They fight crime!