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described a way to make the TSC work on SMP systems, but not gonna tackle it for now (too little benefit).

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also added a bugfix from someone whom i sent the source (hrt_origin now
correct after switching timer)

This was SVN commit r596.
This commit is contained in:
janwas 2004-06-24 14:04:30 +00:00
parent 2b7491d159
commit ce8f5d3520
1 changed files with 16 additions and 9 deletions
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25
source/lib/sysdep/win/wtime.cpp
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@ -35,6 +35,7 @@
//#define NO_TSC
// automatic module init (before main) and shutdown (before termination)
#pragma data_seg(".LIB$WIA")
WIN_REGISTER_FUNC(wtime_init);
#pragma data_seg(".LIB$WTA")
@ -127,12 +128,13 @@ static int choose_impl()
//
// issues:
// - multiprocessor systems: may be inconsistent across CPUs.
// could fix by keeping per-CPU timer state, but we'd need
// GetCurrentProcessorNumber (only available on Win Server 2003).
// spinning off a thread with set CPU affinity is too slow
// (we may have to wait until the next timeslice).
// we could discard really bad values, but that's still inaccurate.
// => unsafe.
// having a high-priority thread with set CPU affinity read the TSC
// might work, but would be rather slow. could fix the problem by
// keeping per-CPU timer state (freq and delta). we'd use the APIC ID
// (cpuid, function 1) or GetCurrentProcessorNumber (only available
// on Win Server 2003) to determine the CPU. however, this is
// too much work for little benefit ATM, so call it unsafe.
// - deep sleep modes: TSC may not be advanced.
// not a problem though, because if the TSC is disabled, the CPU
// isn't doing any other work, either.
@ -306,14 +308,20 @@ static int reset_impl_lk()
// don't call hrt_time to avoid recursive lock.
CHECK_ERR(choose_impl());
// post: hrt_impl != HRT_NONE, hrt_nominal_freq > 0
assert(hrt_impl != HRT_NONE && hrt_nominal_freq > 0);
hrt_freq = (double)hrt_nominal_freq;
// if impl has changed, re-base tick counter.
// want it 0-based, but it must not go backwards WRT previous reading.
if(old_impl != hrt_impl)
{
// have to clear hrt_origin before it's used by ticks_lk.
// thanks to Andre Loker for reporting this bug.
hrt_origin = 0;
hrt_origin = ticks_lk() - (i64)(old_time * hrt_freq);
}
return 0;
}
@ -435,9 +443,8 @@ lock();
hrt_cal_time = hrt_cur;
ms_cal_time = ms_cur;
// we're called from a WinMM event, so the timer has just been updated.
// no need to determine tick / compensate.
// // we're called from a WinMM event, so the timer has just been updated.
// // no need to determine tick / compensate.
// double dt = ms_ds; // actual elapsed time since last calibration
// double hrt_err = ms_ds - hrt_ds;
// double hrt_abs_err = fabs(hrt_err);