contrib: add a write microbenchmark to perf.py
I'm adding some performance logging to ui.write - this benchmark lets us
confirm that the cost of that logging is acceptably low.
At this point, the microbenchmark on Linux over SSH shows:
! wall 3.213560 comb 0.410000 user 0.350000 sys 0.060000 (best of 4)
while on the Mac locally, it shows:
! wall 0.342325 comb 0.180000 user 0.110000 sys 0.070000 (best of 20)
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If you just want a checklist to follow, you can go straight to
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If you can't run the entire testsuite for some reason (it can be
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273ce12ad8f1` will report some style violations on a very old commit).