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perf; Do not allow the backends to optimize away the clear before sync

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The importance of writing to the scratch surface before retrieving an
image is that it makes that the write lands in the server queue, as well
as the GetImage, in order to serialise the timer against all the
operations.

Reported-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
This commit is contained in:
Chris Wilson 2013-01-28 10:03:54 +00:00
parent d9d5adec25
commit 3c18bae20e
1 changed files with 7 additions and 3 deletions
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10
perf/cairo-perf-trace.c
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@ -171,10 +171,12 @@ done:
}
static void
clear_surface (cairo_surface_t *surface)
fill_surface (cairo_surface_t *surface)
{
cairo_t *cr = cairo_create (surface);
cairo_set_operator (cr, CAIRO_OPERATOR_CLEAR);
/* This needs to be an operation that the backends can't optimise away */
cairo_set_source_rgba (cr, 0.5, 0.5, 0.5, 0.5);
cairo_set_operator (cr, CAIRO_OPERATOR_OVER);
cairo_paint (cr);
cairo_destroy (cr);
}
@ -714,6 +716,8 @@ cairo_perf_trace (cairo_perf_t *perf,
1, 1,
CAIRO_BOILERPLATE_MODE_PERF,
&args.closure);
fill_surface(args.surface); /* remove any clear flags */
if (perf->observe) {
cairo_surface_t *obs;
obs = cairo_surface_create_observer (args.surface,
@ -768,7 +772,7 @@ cairo_perf_trace (cairo_perf_t *perf,
fill[i] = _cairo_time_from_s (1.e-9 * cairo_device_observer_fill_elapsed (observer));
glyphs[i] = _cairo_time_from_s (1.e-9 * cairo_device_observer_glyphs_elapsed (observer));
} else {
clear_surface (args.surface); /* queue a write to the sync'ed surface */
fill_surface (args.surface); /* queue a write to the sync'ed surface */
cairo_perf_timer_stop ();
times[i] = cairo_perf_timer_elapsed ();
}