on 03/12/2010 20:05 Jung-uk Kim said the following: > On Friday 03 December 2010 12:26 pm, Andriy Gapon wrote: >> FreeBSD uses cpu_ticks [function pointer] in a few places for a few >> things like process CPU time accounting. On x86 cpu_ticks always >> points to rdtsc. If TSC is not invariant that leads to incorrect >> accounting of "CPU ticks". The code pretends to try to handle >> changing cpufreq levels, but does that incorrectly. > > Arg... Probably it is my fault. :-( > >> I think that we could use a selected timecounter instead of "raw" >> TSC if the latter is not invariant. In this case cpu_ticks calls >> would be slightly costlier, but always correct. >> >> The change is quite trivial: >> http://people.freebsd.org/~avg/tsc-cputicker.diff >> >> What do you think? > > Why don't we just fix it properly?
Patch? :-) It seems that it is not too trivial to do and is prone to error accumulation given how the ticks are added up. Besides, why using a timecounter would not be a proper fix? >> P.S. it's probably a good idea to merge i386 and amd64 tsc.c files >> into a common x86 version, which would be the same as i386 version, >> which seems to be generic enough. > > Agreed. Cool! -- Andriy Gapon _______________________________________________ freebsd-current@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
