Fabian Keil <freebsd-listen_at_fabiankeil.de> wrote: > At least on my system, timestamp offsets can only can be relied > on with either kern.timecounter.hardware=TSC or with C3 > states disabled, though. > > Measuring the elapsed time (in ms) between events that happen > in roughly 1 second intervals with kern.timecounter.hardware=HPET > and dev.cpu.0.cx_lowest=C2: > > elapsed > value ------------- Distribution ------------- count > 990 | 0 > 1000 |_at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at_ 57 > 1010 | 0 > 1020 | 0 > 1030 |_at_ 1 > 1040 | 0 > > elapsed avg 1007 > > And doing the same with dev.cpu.0.cx_lowest=C3: > > elapsed > value ------------- Distribution ------------- count > 40 | 0 > 50 |_at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at__at_ 28 > 60 |_at__at__at__at__at__at__at_ 10 > 70 |_at__at__at_ 5 > 80 |_at_ 1 > 90 | 0 > 100 |_at_ 2 > 110 |_at_ 2 > 120 |_at_ 2 > 130 | 0 > 140 |_at_ 1 > 150 |_at_ 1 > 160 |_at_ 1 > 170 |_at_ 1 > 180 | 0 > 190 | 0 > 200 | 0 > 210 | 0 > 220 |_at_ 1 > 230 |_at_ 1 > 240 | 0 > 250 | 0 > 260 | 0 > 270 | 0 > 280 | 0 > 290 |_at_ 1 > 300 |_at_ 1 > 310 | 0 > 320 |_at_ 1 > 330 | 0 > > elapsed avg 90 Copying over some code from mips seems to fix this: http://www.freebsd.org/cgi/query-pr.cgi?pr=amd64/169379 Fabian
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