diff options
| author | zml <zml@FreeBSD.org> | 2012-06-04 16:04:01 +0000 |
|---|---|---|
| committer | zml <zml@FreeBSD.org> | 2012-06-04 16:04:01 +0000 |
| commit | af0c1bd2f507f03ce71696fff76105d95285533a (patch) | |
| tree | 3f7b5012961593e655e3f4bfd5da1b4a9963591e /sys/cddl/dev/dtrace | |
| parent | d351cdcdf9c9f7fac31717fabfd7259ba1e2e08c (diff) | |
| download | FreeBSD-src-af0c1bd2f507f03ce71696fff76105d95285533a.zip FreeBSD-src-af0c1bd2f507f03ce71696fff76105d95285533a.tar.gz | |
Fix DTrace TSC skew calculation:
The skew calculation here is exactly backwards. We were able to repro
it on a multi-package ESX server running a FreeBSD VM, where the TSCs
can be pretty evil.
MFC after: 1 week
Submitted by: Jeff Ford <jeffrey.ford2@isilon.com>
Reviewed by: avg, gnn
Diffstat (limited to 'sys/cddl/dev/dtrace')
| -rw-r--r-- | sys/cddl/dev/dtrace/amd64/dtrace_subr.c | 2 | ||||
| -rw-r--r-- | sys/cddl/dev/dtrace/i386/dtrace_subr.c | 2 |
2 files changed, 2 insertions, 2 deletions
diff --git a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c index d2a1cf1..d80287b 100644 --- a/sys/cddl/dev/dtrace/amd64/dtrace_subr.c +++ b/sys/cddl/dev/dtrace/amd64/dtrace_subr.c @@ -446,7 +446,7 @@ dtrace_gethrtime() * (see nsec_scale calculations) taking into account 32-bit shift of * the higher half and finally add. */ - tsc = rdtsc() + tsc_skew[curcpu]; + tsc = rdtsc() - tsc_skew[curcpu]; lo = tsc; hi = tsc >> 32; return (((lo * nsec_scale) >> SCALE_SHIFT) + diff --git a/sys/cddl/dev/dtrace/i386/dtrace_subr.c b/sys/cddl/dev/dtrace/i386/dtrace_subr.c index b52097b..e0e9750 100644 --- a/sys/cddl/dev/dtrace/i386/dtrace_subr.c +++ b/sys/cddl/dev/dtrace/i386/dtrace_subr.c @@ -447,7 +447,7 @@ dtrace_gethrtime() * (see nsec_scale calculations) taking into account 32-bit shift of * the higher half and finally add. */ - tsc = rdtsc() + tsc_skew[curcpu]; + tsc = rdtsc() - tsc_skew[curcpu]; lo = tsc; hi = tsc >> 32; return (((lo * nsec_scale) >> SCALE_SHIFT) + |
