[PATCH] perf/x86/amd: Use faster rdpmc instruction when waiting for overflow

From: Kim Phillips
Date: Tue Nov 16 2021 - 12:08:25 EST


The relatively new amd_pmu_wait_on_overflow uses rdmsr.
Update it to use the faster rdpmc instruction.

Signed-off-by: Kim Phillips <kim.phillips@xxxxxxx>
---
arch/x86/events/amd/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/amd/core.c b/arch/x86/events/amd/core.c
index 9687a8aef01c..c36cb0c6f9e1 100644
--- a/arch/x86/events/amd/core.c
+++ b/arch/x86/events/amd/core.c
@@ -587,6 +587,8 @@ static void amd_pmu_cpu_dead(int cpu)

static void amd_pmu_wait_on_overflow(int idx)
{
+ struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
+ struct hw_perf_event *hwc = &cpuc->events[idx]->hw;
unsigned int i;
u64 counter;

@@ -596,7 +598,7 @@ static void amd_pmu_wait_on_overflow(int idx)
* forever...
*/
for (i = 0; i < OVERFLOW_WAIT_COUNT; i++) {
- rdmsrl(x86_pmu_event_addr(idx), counter);
+ rdpmcl(hwc->event_base_rdpmc, counter);
if (counter & (1ULL << (x86_pmu.cntval_bits - 1)))
break;

--
2.32.0