perf/x86/intel: Remove division from the intel_pmu_drain_pebs_nhm() hot path

Only do the division in case we have to print the result out in a warning.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-43nl31erfbajwpfj254f6zji@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index f364c13ddaa6..655d591b57a0 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -944,7 +944,7 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
         struct perf_event *event = NULL;
         void *at, *top;
         u64 status = 0;
-        int bit, n;
+        int bit;
 
         if (!x86_pmu.pebs_active)
                 return;
@@ -954,16 +954,16 @@ static void intel_pmu_drain_pebs_nhm(struct pt_regs *iregs)
 
         ds->pebs_index = ds->pebs_buffer_base;
 
-        n = (top - at) / x86_pmu.pebs_record_size;
-        if (n <= 0)
+        if (unlikely(at > top))
                 return;
 
         /*
          * Should not happen, we program the threshold at 1 and do not
          * set a reset value.
          */
-        WARN_ONCE(n > x86_pmu.max_pebs_events,
-                  "Unexpected number of pebs records %d\n", n);
+        WARN_ONCE(top - at > x86_pmu.max_pebs_events * x86_pmu.pebs_record_size,
+                  "Unexpected number of pebs records %ld\n",
+                  (top - at) / x86_pmu.pebs_record_size);
 
         for (; at < top; at += x86_pmu.pebs_record_size) {
                 struct pebs_record_nhm *p = at;