Comment 23 for bug 1951032

Ran the tests against -updates and -proposed on a Pi 4, Pi 3B+, and Pi Zero 2 with the following results:

= Raspberry Pi 4 =

   length | before (MiB/s) | after (MiB/s) | delta
----------|----------------|----------------|----------
    32768 | 83.58 | 83.03 | -0.66%
    65536 | 156.08 | 155.69 | -0.25%
   131072 | 292.88 | 291.93 | -0.33%
   262144 | 543.00 | 550.95 | 1.47%
   524288 | 596.54 | 612.14 | 2.62%
  1048576 | 640.72 | 643.76 | 0.47%

= Raspberry Pi 3B+ =

   length | before (MiB/s) | after (MiB/s) | delta
----------|----------------|----------------|----------
    32768 | 55.55 | 55.38 | -0.31%
    65536 | 98.39 | 98.36 | -0.03%
   131072 | 173.72 | 169.80 | -2.26%
   262144 | 165.05 | 161.24 | -2.31%
   524288 | 146.80 | 147.16 | 0.25%
  1048576 | 221.23 | 221.32 | 0.04%

= Raspberry Pi Zero 2 =

   length | before (MiB/s) | after (MiB/s) | delta
----------|----------------|----------------|----------
    32768 | 39.09 | 39.32 | 0.58%
    65536 | 70.09 | 70.33 | 0.34%
   131072 | 125.40 | 122.88 | -2.01%
   262144 | 133.79 | 133.76 | -0.02%
   524288 | 134.59 | 133.84 | -0.56%
  1048576 | 203.99 | 203.89 | -0.04%

Looking much better than before; some mild improvement (and not too much cost) on the Pi 4 (the only platform where arm64 typically makes sense in the Pi series), and only minor degradation in the rest.