2 files changed, 28 insertions, 7 deletions

diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 6bc250039738..4f9d39ecdc05 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -373,6 +373,9 @@ struct hw_perf_counter {
         u64                             sample_period;
         atomic64_t                      period_left;
         u64                             interrupts;
+
+        u64                             freq_count;
+        u64                             freq_interrupts;
 #endif
 };
 
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index f8390668c391..47c92fb927f2 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1187,8 +1187,9 @@ static void perf_log_period(struct perf_counter *counter, u64 period);
 static void perf_adjust_freq(struct perf_counter_context *ctx)
 {
         struct perf_counter *counter;
+        struct hw_perf_counter *hwc;
         u64 interrupts, sample_period;
-        u64 events, period;
+        u64 events, period, freq;
         s64 delta;
 
         spin_lock(&ctx->lock);
@@ -1196,8 +1197,10 @@ static void perf_adjust_freq(struct perf_counter_context *ctx)
                 if (counter->state != PERF_COUNTER_STATE_ACTIVE)
                         continue;
 
-                interrupts = counter->hw.interrupts;
-                counter->hw.interrupts = 0;
+                hwc = &counter->hw;
+
+                interrupts = hwc->interrupts;
+                hwc->interrupts = 0;
 
                 if (interrupts == MAX_INTERRUPTS) {
                         perf_log_throttle(counter, 1);
@@ -1208,20 +1211,35 @@ static void perf_adjust_freq(struct perf_counter_context *ctx)
                 if (!counter->attr.freq || !counter->attr.sample_freq)
                         continue;
 
-                events = HZ * interrupts * counter->hw.sample_period;
+                if (counter->attr.sample_freq < HZ) {
+                        freq = counter->attr.sample_freq;
+
+                        hwc->freq_count += freq;
+                        hwc->freq_interrupts += interrupts;
+
+                        if (hwc->freq_count < HZ)
+                                continue;
+
+                        interrupts = hwc->freq_interrupts;
+                        hwc->freq_interrupts = 0;
+                        hwc->freq_count -= HZ;
+                } else
+                        freq = HZ;
+
+                events = freq * interrupts * hwc->sample_period;
                 period = div64_u64(events, counter->attr.sample_freq);
 
-                delta = (s64)(1 + period - counter->hw.sample_period);
+                delta = (s64)(1 + period - hwc->sample_period);
                 delta >>= 1;
 
-                sample_period = counter->hw.sample_period + delta;
+                sample_period = hwc->sample_period + delta;
 
                 if (!sample_period)
                         sample_period = 1;
 
                 perf_log_period(counter, sample_period);
 
-                counter->hw.sample_period = sample_period;
+                hwc->sample_period = sample_period;
         }
         spin_unlock(&ctx->lock);
 }