Messages in this thread | | | Date | Wed, 26 Mar 2003 08:12:51 -0800 | From | george anzinger <> | Subject | Re: System time warping around real time problem - please help |
| |
Alan Cox wrote: > On Wed, 2003-03-26 at 02:28, george anzinger wrote: > >>Stands for Time Stamp Counter. It is a special cpu register that >>basically counts cpu cycles. Some times (incorrectly me thinks) it is >>affected by power management code which slows the cpu by changing the >>cpu frequency. > > > Not incorrectly. It counts cpu clocks, its designed for profiling and > the like. There is no guarantee in any Intel MP standard that the clocks > are synched up.
> I seem to recall a different notion of correctness from Andy Grover... but memory may deceive :(
As for sync, I would think it is a mother board issue.
But as you say, Intel should put in a usable counter. The HPET seems like it has the capabilities, however, I suspect that it is a slow read. Any idea how many cycles it takes to do a memory mapped I/O access? -- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml
- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |