diff options
| author | Ali Mashtizadeh <mashti@uwaterloo.ca> | 2026-03-23 20:21:21 +0000 |
|---|---|---|
| committer | Mitchell Horne <mhorne@FreeBSD.org> | 2026-03-23 20:21:21 +0000 |
| commit | 39515d8b623a2be39d0c42a537fd9a17c417ff6e (patch) | |
| tree | 3c012b8e750855bc7c63db9f47d9a1866db1d447 | |
| parent | 47402c9422ec6c9ba76d96414f5a08bd35a9e1fd (diff) | |
hwpmc: Use rdtsc instead of rdtscp for timestamps
No need for a barrier here, we are inside an NMI handler and executing a
number of serializing instructions with stronger semantics. Reducing
this overhead will increase our maximum safe sampling rate.
Tested by: Paulo Fragoso <paulo@nlink.com.br>
Reviewed by: mhorne
MFC after: 1 week
Sponsored by: Netflix
Pull Request: https://github.com/freebsd/freebsd-src/pull/2076
| -rw-r--r-- | sys/dev/hwpmc/hwpmc_mod.c | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/sys/dev/hwpmc/hwpmc_mod.c b/sys/dev/hwpmc/hwpmc_mod.c index fb1fdf832398..6133b52b516f 100644 --- a/sys/dev/hwpmc/hwpmc_mod.c +++ b/sys/dev/hwpmc/hwpmc_mod.c @@ -818,11 +818,9 @@ pmc_force_context_switch(void) uint64_t pmc_rdtsc(void) { -#if defined(__i386__) || defined(__amd64__) - if (__predict_true(amd_feature & AMDID_RDTSCP)) - return (rdtscp()); - else - return (rdtsc()); +#if defined(__i386__) + /* Unfortunately get_cyclecount on i386 uses cpu_ticks. */ + return (rdtsc()); #else return (get_cyclecount()); #endif |