[lkml]   [2000]   [Nov]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: rdtsc to mili secs?
Anton Blanchard wrote:
> > > fast_gettimeoffset_quotient, see do_fast_gettimeoffset().
> >
> > Also remember that the TSC may not be available due to the chip era, chip
> > bugs or running SMP with non matched CPU clocks.
> When I boot my thinkpad 600e off battery and then change to AC power,
> gettimeofday has a nasty habit of going backwards. Stephen Rothwell
> tells me it is one of these machines in which the cycle counter
> slows down when power is removed.
> This means our offset calculations in do_fast_gettimeoffset are way off
> and taking a reading just before a timer tick and just after results in
> a negative interval. Perhaps we should disable tsc based gettimeofday
> for these type of machines.

This issue, and all related issues, need to be taken care of for all
changing CPUs from Intel, AMD and Transmeta. Is the answer of "howto
userland programs correctly with a speed changing cpu" in a FAQ

- Antony Suter ( "Examiner" openpgp:71ADFC87
- "And how do you store the nuclear equivalent of the universal
- solvent?"
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
Please read the FAQ at

 \ /
  Last update: 2005-03-22 12:45    [W:0.070 / U:1.500 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site