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Unconditionally use binuptime(9) for get_cyclecount(9) on i386. Since this

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function is almost exclusively used for random harvesting, there is no need
for micro-optimization.  Adjust the manual page accordingly.
This commit is contained in:
Jung-uk Kim 2011-03-15 17:14:26 +00:00
parent 35daccccce
commit d8ea2a492e
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=219672
2 changed files with 6 additions and 11 deletions
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8
share/man/man9/get_cyclecount.9
View File

@ -24,7 +24,7 @@
.\"
.\" $FreeBSD$
.\"
.Dd October 24, 2009
.Dd March 15, 2011
.Dt GET_CYCLECOUNT 9
.Os
.Sh NAME
@ -65,14 +65,14 @@ do not have such a register,
so
.Fn get_cyclecount
on these platforms
returns a (non-monotonic) combination of numbers
returns a (monotonic) combination of numbers
represented by the
structure returned by
.Xr binuptime 9 .
.Pp
The
.Tn Pentium
processors all use the
.Tn AMD64 and Intel 64
processors use the
.Li TSC
register.
.Pp

9
sys/i386/include/cpu.h
View File

@ -70,15 +70,10 @@ void swi_vm(void *);
static __inline uint64_t
get_cyclecount(void)
{
#if defined(I486_CPU) || defined(KLD_MODULE)
struct bintime bt;
if (!tsc_present) {
binuptime(&bt);
return ((uint64_t)bt.sec << 56 | bt.frac >> 8);
}
#endif
return (rdtsc());
binuptime(&bt);
return ((uint64_t)bt.sec << 56 | bt.frac >> 8);
}
#endif