Hi, On 2025-07-16 18:24:33 -0400, Tom Lane wrote: > ... BTW, another resource worth looking at is src/bin/pg_test_timing/ > which we just improved a few days ago [1]. What I see on two different > Linux-on-Intel boxes is that the loop time that that reports is 16 ns > and change, and the clock readings appear accurate to full nanosecond > precision. Changing instr_time.h to use CLOCK_MONOTONIC_COARSE, the > loop time drops to a bit over 5 ns, which would certainly be a nice > win if it were cost-free. But the clock precision degrades to 1 ms.
FWIW, switching to using rtscp for timestamp acqusition substantially reduces timing overhead, albeit not quite as low as 5ns, without loosing any meaningful precision. The patch from [1] needs to be rebased unfortunately. Separately, the amount of work we're now doing for each loop iteration in test_timing() got to start having some effect, no? Greetings, Andres [1] https://postgr.es/m/CAP53PkzO2KpscD-tgFW_V-4WS%2BvkniH4-B00eM-e0bsBF-xUxg%40mail.gmail.com
