Time consumption, lv_meter, lv_arc ? STM32F746


With my STM32F746 board I noticed that the lv_meter and lv_arc function sometimes lead to longer interruptions, up to 30ms. See below my test code and measurements. Is this normal?

First I commented out all functions, the LED toggles more or less regularly every 2ms.

lv_meter (random value) has the longest interruptions, partly up to 30ms!
lv_meter (fixed value) has partly 10ms interruptions
lv_arc (random value) has partly 10ms interruptions
lv_arc (fixed value) is OK/regular,
lv_chart (random value) is OK/regular
lv_chart (fixed value) is OK/regular

screen_meter_1_scale_1_ndimg_0 = lv_meter_add_needle_line(ui.screen_meter_1, screen_meter_1_scale_1, 4, lv_color_make(0xff, 0x00, 0x00), -30);
    while (1)
        if( ( millis()-lastMillis2 ) > 4){
        	lastMillis2 = millis();

    	if( ( millis()-lastMillis1 ) > 1){
    		HAL_GPIO_TogglePin(GPIOI, GPIO_PIN_8); //LED 101
    		lv_meter_set_indicator_value(ui.screen_meter_1, screen_meter_1_scale_1_ndimg_0, lv_rand(0,1000) );
    		lv_meter_set_indicator_value(ui.screen_meter_1, screen_meter_1_scale_1_ndimg_0, 500 );
    		lv_arc_set_value(ui.screen_arc_1, lv_rand(0,1000));
    		lv_arc_set_value(ui.screen_arc_1, 500);
    		lv_chart_set_value_by_id(ui.screen_chart_1, screen_chart_1_0, countChart, lv_rand(0,1000));
    		lv_chart_set_value_by_id(ui.screen_chart_1, screen_chart_1_0, countChart, 500);


    		lastMillis1 = millis();

NO function:

lv_meter (random value):

lv_meter (fixed value):

lv_arc (random value):

lv_arc (fixed value):