compared to tgro5:

tgro0   py -> noise (ZEO, NEO/pylite, NEO/pysql, partly neo/go)
tgro10  py=no-noise, tpy~=tgro5; tgo serial~same, +prefetch more noise (?) 40|65
tgro15  lat_tcp 1B 49->45 sometime (consistently) otherwise more-or-less same
tgro20  lat_tcp 4K 170µs->167µs (c)
tgro25  lat_tcp 4K 170µs->167µs (c), lat_tcp 4K 175 -> 171µs (go)
        ZEOv a bit
        go-go + prefetch !sha1 -> noise + higher (~65µs -> 70 - 110µs)

txc40µs4f seems to be worse than txc200µs4f