[PATCH 8/9] x86, perf: Optimize v4 LBR unfreezing

Andi Kleen
2015-05-10T19:23:55Z

From: Andi Kleen <ak@linux.intel.com>

In Arch perfmon v4 the GLOBAL_STATUS reset automatically unfreezes
LBRs. So no need to do it manually in the LBR code. Add a check
to skip it.

v2: Move test up to beginning of function.
Signed-off-by: Andi Kleen <ak@linux.intel.com>
---
arch/x86/kernel/cpu/perf_event_intel_lbr.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_lbr.c b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
index 6c48c97..ae54ea9 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_lbr.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_lbr.c
@@ -139,6 +139,13 @@ static void __intel_pmu_lbr_enable(bool pmi)
u64 debugctl, lbr_select = 0, orig_debugctl;

/*
+ * No need to unfreeze manually, as v4 can do that as part
+ * of the GLOBAL_STATUS ack.
+ */
+ if (pmi && x86_pmu.version >= 4)
+ return;
+
+ /*
* No need to reprogram LBR_SELECT in a PMI, as it
* did not change.
*/
--
1.9.3