Messages in this thread |  | | Date | Mon, 26 Aug 2002 21:42:26 +0200 | From | Pavel Machek <> | Subject | Re: [PATCH] tsc-disable_B9 |
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Hi! > > >> And following your argument that these apps have been silenty broken > > >> since 1999, if there's no broken app out there, nobody will ever get the > > >> instruction fault. If there's any app broken out there we probably like > > > > > > No. rdtsc is still usefull if you are clever and statistically filter > > > out. Also rdtsc provides you number of cycles, so if you want to know > > > how many cycles mov %eax,%ebx takes, you can do that even on > > > speedstep. Anything that correlates rdtsc to real time is broken, however. > > > > It's not correlating it to real time that's the problem. It's getting resceduled > > inbetween calls that hurts. Take your example. > > > > rdtsc > > mov %eax,%ebx > > <- get rescheduled here > > rdtsc > > > > Broken. May even take negative "time". > > > > M. > > The CPU counters are synchronized on SMP machines. How can you > ever get negative time? Even GHz machines take several months > to wrap the count.
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