Author: markj
Date: Sun May 11 16:48:36 2014
New Revision: 265882
URL: http://svnweb.freebsd.org/changeset/base/265882
Log:
MFC r236566 (by zml):
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.
Modified:
stable/9/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
stable/9/sys/cddl/dev/dtrace/i386/dtrace_subr.c
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/cddl/dev/dtrace/amd64/dtrace_subr.c
==============================================================================
--- stable/9/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Sun May 11 16:34:17
2014 (r265881)
+++ stable/9/sys/cddl/dev/dtrace/amd64/dtrace_subr.c Sun May 11 16:48:36
2014 (r265882)
@@ -445,7 +445,7 @@ 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) +
Modified: stable/9/sys/cddl/dev/dtrace/i386/dtrace_subr.c
==============================================================================
--- stable/9/sys/cddl/dev/dtrace/i386/dtrace_subr.c Sun May 11 16:34:17
2014 (r265881)
+++ stable/9/sys/cddl/dev/dtrace/i386/dtrace_subr.c Sun May 11 16:48:36
2014 (r265882)
@@ -454,7 +454,7 @@ 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) +
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