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>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index f364c13..655d591 100644 (file)
--- 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;