RE: [Valgrind-users] start_rstsc_calibration causes illegalinstruction crash

[Jeremy F. <je...@go...>]

On Mon, 2003-11-24 at 03:46, Nicholas Nethercote wrote:
> On Fri, 21 Nov 2003, Daniel Goertzen wrote:
> 
> > Attached are two patches:  The first one, valgrind-cx486.patch, works around
> > the CPUID and RTDSC instructions in coregrind/.
> 
> The RTDSC patch removes a lot of code, which is good.  What are the pros
> and cons of gettimeofday() vs. rdtsc?  I don't know much about timing
> issues, but gettimeofday() seems simpler and would avoid the problems with
> laptops that RTDSC has?  Maybe gettimeofday() makes
> VG_(read_millisecond_timer)() more expensive, as it requires a system
> call?  Any other relevant issues?

It would certainly be nice to use the TSC as a timebase if we can be
sure it is reliable, but I don't know how we can tell.  The CVS HEAD
version of Valgrind makes much less use of read_millisecond_timer, so I
don't think its efficiency is a huge issue.

	J