perf ui tui progress: Don't force a refresh during progress update

Each call to tui_progress__update() would forcibly refresh the entire
screen. This is somewhat inefficient and causes noticable flickering
during the startup of perf-report, especially on large/slow terminals.

It looks like the force-refresh in tui_progress__update() serves no
purpose other than to clear the screen so that the progress bar of a
previous operation does not subsume that of a subsequent operation. But
we can do just that in a much more efficient manner by clearing only the
region that a previous progress bar may have occupied before repainting
the new progress bar. Then the force-refresh could be removed with no
change in visuals.

This patch disables the slow force-refresh in tui_progress__update() and
instead calls SLsmg_fill_region() on the entire area that the progress
bar may occupy before repainting it. This change makes the startup of
perf-report much faster and appear much "smoother".

It turns out that this was a big bottleneck in the startup speed of
perf-report -- with this patch, perf-report starts up ~2x faster (1.1s
vs 0.55s) on my machines. (These numbers were measured by running "time
perf report" on an 8MB perf.data and pressing 'q' immediately.)

Signed-off-by: Patrick Palka <[e-mail]>
Acked-by: Ingo Molnar <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Paul Mackerras <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/ui/tui/progress.c

···
 	if (p->total == 0)
 		return;
 
-	ui__refresh_dimensions(true);
+	ui__refresh_dimensions(false);
 	pthread_mutex_lock(&ui__lock);
 	y = SLtt_Screen_Rows / 2 - 2;
 	SLsmg_set_color(0);
 	SLsmg_draw_box(y, 0, 3, SLtt_Screen_Cols);
 	SLsmg_gotorc(y++, 1);
 	SLsmg_write_string((char *)p->title);
+	SLsmg_fill_region(y, 1, 1, SLtt_Screen_Cols - 2, ' ');
 	SLsmg_set_color(HE_COLORSET_SELECTED);
 	bar = ((SLtt_Screen_Cols - 2) * p->curr) / p->total;
 	SLsmg_fill_region(y, 1, 1, bar, ' ');