Hi all,
In Unity, at least, we're pushing around quite a lot of GVariants, and
while it's not slow, I was wondering if we could make even faster. If
nothing, it would be a fun exercise :-)
The basic idea I have is stolen from Java's Boolean and Integer classes
where they have singletons to help cut some corners in the garbage
collector and comparison methods. In Java that makes a big difference.
(for Integer they cache numbers up to 128 I believe)
I made a very simple benchmark to test something similar with GVariants,
which I have attached to this mail. Simulating that the TRUE GVariant is
a singleton I get numbers ala:
$ ./gvariant-singletons
CREATE 1000 : 0.000781s
DESTROY 1000 : 0.000430s
CREATE 1000 : 0.000042s (sngltn)
DESTROY 1000 : 0.000039s (sngltn)
Running the test numerous times I see speedups in the range of 5-20
times. Not mighty surprising - just verifies that ref() is faster than
new allocations, but still good to see it in raw numbers.
One could do something similar for low valued integers - I am mostly
thinking those that would be in the range of your average enum.
So I think this looks pretty interesting, and I'll probably look into it
over the next days; but any comments (or showstoppers?!) are most welcome.
And yes, yes, I know this is another slap in the face for the valgrind
camp. Sorry!
Cheers,
Mikkel
/* gcc gvariant-singletons.c -o gvariant-singletons $(pkg-config --cflags --libs glib-2.0 gobject-2.0) */
#include <glib.h>
#include <glib/gprintf.h>
#define N_VARIANTS 1000
void
main ()
{
GVariant *gvTRUE, *gvFALSE;
GTimer *timer;
GVariant **variants;
int i;
g_type_init ();
variants = g_new (GVariant*, N_VARIANTS);
gvTRUE = g_variant_new_boolean (TRUE);
gvFALSE = g_variant_new_boolean (FALSE);
/* Dummy run */
for (i = 0; i < N_VARIANTS; i++)
{
variants[i] = g_variant_new_boolean (TRUE);
g_variant_unref (variants[i]);
}
/* NORMAL - no singletons */
timer = g_timer_new ();
for (i = 0; i < N_VARIANTS; i++)
{
variants[i] = g_variant_new_boolean (TRUE);
}
g_printf ("CREATE %i : %fs\n", N_VARIANTS, g_timer_elapsed (timer, NULL));
g_timer_start (timer);
for (i = 0; i < N_VARIANTS; i++)
{
g_variant_unref (variants[i]);
}
g_printf ("DESTROY %i : %fs\n", N_VARIANTS, g_timer_elapsed (timer, NULL));
/* With singleton booleans */
g_timer_start (timer);
for (i = 0; i < N_VARIANTS; i++)
{
variants[i] = g_variant_ref (gvTRUE);
}
g_printf ("CREATE %i : %fs (sngltn)\n", N_VARIANTS, g_timer_elapsed (timer, NULL));
g_timer_start (timer);
for (i = 0; i < N_VARIANTS; i++)
{
g_variant_unref (variants[i]);
}
g_printf ("DESTROY %i : %fs (sngltn)\n", N_VARIANTS, g_timer_elapsed (timer, NULL));
g_free (variants);
g_variant_unref (gvTRUE);
g_variant_unref (gvFALSE);
}
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