[cairo] Question：cairo_paint or cairo_fill low efficiency

[唐博]

cairo_surface_t * surfaceSrc = cairo_image_surface_create(CAIRO_FORMAT_RGB16_565, 917, 917);
cairo_surface_t * surfaceDst = cairo_image_surface_create(CAIRO_FORMAT_RGB16_565, 480, 800);
cairo_t * crDst = cairo_create(surfaceDst);

cairo_scale(cr, 2.0, 2.0);

cairo_set_source_surface(crDst, surfaceSrc, 0, 0);
cairo_paint(crDst);

when it runs on android os, the efficiency is very low. if use cairo_scale(cr, 1.0, 1.0) , no zoomratio, it runs 

very fast. Why ? Anyone tell me? 
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