diff --git a/garnet/lib/system_monitor/dockyard/dockyard.cc b/garnet/lib/system_monitor/dockyard/dockyard.cc
index 3d21e0af..b5d43d69 100644
--- a/garnet/lib/system_monitor/dockyard/dockyard.cc
+++ b/garnet/lib/system_monitor/dockyard/dockyard.cc
@@ -103,6 +103,10 @@
 
 }  // namespace
 
+bool StreamSetsRequest::HasFlag(StreamSetsRequestFlags flag) const {
+  return (flags & flag) != 0;
+}
+
 Dockyard::Dockyard()
     : server_thread_(nullptr),
       stream_name_handler_(nullptr),
@@ -238,7 +242,7 @@
         default:
           break;
       }
-      if ((request.flags & StreamSetsRequest::NORMALIZE) != 0) {
+      if (request.HasFlag(StreamSetsRequest::NORMALIZE)) {
         NormalizeResponse(*stream_id, sample_stream, request, &samples);
       }
     }
@@ -258,9 +262,13 @@
   for (uint64_t sample_n = 0; sample_n < request.sample_count; ++sample_n) {
     auto start_time = request.start_time_ns + sample_n * stride;
     auto begin = sample_stream.lower_bound(start_time);
-    auto end = sample_stream.upper_bound(start_time + stride);
+    if (begin == sample_stream.end()) {
+      samples->push_back(NO_DATA);
+      continue;
+    }
+    auto end = sample_stream.lower_bound(start_time + stride);
     SampleValue accumulator = 0ULL;
-    SampleValue count = 0ULL;
+    uint_fast32_t count = 0ULL;
     for (auto i = begin; i != end; ++i) {
       accumulator += i->second;
       ++count;
@@ -268,7 +276,7 @@
     if (count) {
       samples->push_back(accumulator / count);
     } else {
-      samples->push_back(-2ULL);
+      samples->push_back(NO_DATA);
     }
   }
 }
@@ -280,9 +288,13 @@
   for (uint64_t sample_n = 0; sample_n < request.sample_count; ++sample_n) {
     auto start_time = request.start_time_ns + sample_n * stride;
     auto begin = sample_stream.lower_bound(start_time);
-    auto end = sample_stream.upper_bound(start_time + stride);
+    if (begin == sample_stream.end()) {
+      samples->push_back(NO_DATA);
+      continue;
+    }
+    auto end = sample_stream.lower_bound(start_time + stride);
     SampleValue highest = 0ULL;
-    SampleValue count = 0ULL;
+    uint_fast32_t count = 0ULL;
     for (auto i = begin; i != end; ++i) {
       if (highest < i->second) {
         highest = i->second;
@@ -292,7 +304,7 @@
     if (count) {
       samples->push_back(highest);
     } else {
-      samples->push_back(-2ULL);
+      samples->push_back(NO_DATA);
     }
   }
 }
@@ -305,9 +317,13 @@
   for (uint64_t sample_n = 0; sample_n < request.sample_count; ++sample_n) {
     auto start_time = request.start_time_ns + sample_n * stride;
     auto begin = sample_stream.lower_bound(start_time);
-    auto end = sample_stream.upper_bound(start_time + stride);
+    if (begin == sample_stream.end()) {
+      samples->push_back(NO_DATA);
+      continue;
+    }
+    auto end = sample_stream.lower_bound(start_time + stride);
     SampleValue lowest = SAMPLE_MAX_VALUE;
-    SampleValue count = 0ULL;
+    uint_fast32_t count = 0ULL;
     for (auto i = begin; i != end; ++i) {
       if (lowest > i->second) {
         lowest = i->second;
@@ -317,7 +333,7 @@
     if (count) {
       samples->push_back(lowest);
     } else {
-      samples->push_back(-2ULL);
+      samples->push_back(NO_DATA);
     }
   }
 }
@@ -352,11 +368,15 @@
   for (uint64_t sample_n = 0; sample_n < request.sample_count; ++sample_n) {
     auto start_time = request.start_time_ns + sample_n * stride;
     auto begin = sample_stream.lower_bound(start_time);
-    auto end = sample_stream.upper_bound(start_time + stride);
+    if (begin == sample_stream.end()) {
+      samples->push_back(NO_DATA);
+      continue;
+    }
+    auto end = sample_stream.lower_bound(start_time + stride);
     SampleValue accumulator = 0ULL;
     SampleValue highest = 0ULL;
     SampleValue lowest = SAMPLE_MAX_VALUE;
-    SampleValue count = 0ULL;
+    uint_fast32_t count = 0ULL;
     for (auto i = begin; i != end; ++i) {
       auto value = i->second;
       accumulator += value;
@@ -373,7 +393,7 @@
       auto final = average >= overall_average ? highest : lowest;
       samples->push_back(final);
     } else {
-      samples->push_back(-2ULL);
+      samples->push_back(NO_DATA);
     }
   }
 }
@@ -386,9 +406,13 @@
   for (uint64_t sample_n = 0; sample_n < request.sample_count; ++sample_n) {
     auto start_time = request.start_time_ns + sample_n * stride;
     auto begin = sample_stream.lower_bound(start_time - stride);
-    auto end = sample_stream.upper_bound(start_time + stride * 2);
+    if (begin == sample_stream.end()) {
+      samples->push_back(NO_DATA);
+      continue;
+    }
+    auto end = sample_stream.lower_bound(start_time + stride * 2);
     SampleValue accumulator = 0ULL;
-    SampleValue count = 0ULL;
+    uint_fast32_t count = 0ULL;
     for (auto i = begin; i != end; ++i) {
       accumulator += i->second;
       ++count;
@@ -396,7 +420,7 @@
     if (count) {
       samples->push_back(accumulator / count);
     } else {
-      samples->push_back(-2ULL);
+      samples->push_back(NO_DATA);
     }
   }
 }
diff --git a/garnet/lib/system_monitor/dockyard/dockyard.h b/garnet/lib/system_monitor/dockyard/dockyard.h
index fbe49ab..f63cf24 100644
--- a/garnet/lib/system_monitor/dockyard/dockyard.h
+++ b/garnet/lib/system_monitor/dockyard/dockyard.h
@@ -112,6 +112,8 @@
 
   // A StreamInfo::id for each stream of interest.
   std::vector<SampleStreamId> stream_ids;
+
+  bool HasFlag(StreamSetsRequestFlags flag) const;
 };
 
 struct StreamSetsResponse {
diff --git a/garnet/lib/system_monitor/dockyard/dockyard_unittests.cc b/garnet/lib/system_monitor/dockyard/dockyard_unittests.cc
index e4ef307..d1baac9 100644
--- a/garnet/lib/system_monitor/dockyard/dockyard_unittests.cc
+++ b/garnet/lib/system_monitor/dockyard/dockyard_unittests.cc
@@ -99,8 +99,8 @@
   ASSERT_EQ(SAMPLE_COUNT, _response.data_sets[0].size());
   // Check the samples themselves.
   EXPECT_EQ(8ULL, _response.data_sets[0][0]);
-  EXPECT_EQ(10ULL, _response.data_sets[0][1]);
-  EXPECT_EQ(15ULL, _response.data_sets[0][2]);
+  EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][1]);
+  EXPECT_EQ(10ULL, _response.data_sets[0][2]);
   EXPECT_EQ(20ULL, _response.data_sets[0][3]);
   EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][4]);
   EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][5]);
@@ -138,7 +138,7 @@
   EXPECT_EQ(10ULL, _response.data_sets[0][6]);
   EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][7]);
   EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][8]);
-  EXPECT_EQ(20ULL, _response.data_sets[0][9]);
+  EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][9]);
 }
 
 TEST_F(SystemMonitorDockyardTest, RawDataSetsCpu1) {
@@ -193,10 +193,10 @@
   ASSERT_EQ(1UL, _response.data_sets.size());
   ASSERT_EQ(SAMPLE_COUNT, _response.data_sets[0].size());
   // Check the samples themselves.
-  EXPECT_EQ(30ULL, _response.data_sets[0][0]);
-  EXPECT_EQ(71ULL, _response.data_sets[0][1]);
-  EXPECT_EQ(31ULL, _response.data_sets[0][2]);
-  EXPECT_EQ(7ULL, _response.data_sets[0][3]);
+  EXPECT_EQ(15ULL, _response.data_sets[0][0]);
+  EXPECT_EQ(78ULL, _response.data_sets[0][1]);
+  EXPECT_EQ(38ULL, _response.data_sets[0][2]);
+  EXPECT_EQ(8ULL, _response.data_sets[0][3]);
   EXPECT_EQ(18ULL, _response.data_sets[0][4]);
 }
 
@@ -226,10 +226,10 @@
   // Check the samples themselves.
   // CPU 0.
   EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][0]);
-  EXPECT_EQ(10ULL, _response.data_sets[0][1]);
+  EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[0][1]);
   // CPU 1.
   EXPECT_EQ(10ULL, _response.data_sets[1][0]);
-  EXPECT_EQ(100ULL, _response.data_sets[1][1]);
+  EXPECT_EQ(dockyard::NO_DATA, _response.data_sets[1][1]);
   // CPU 2.
   EXPECT_EQ(46ULL, _response.data_sets[2][0]);
   EXPECT_EQ(17ULL, _response.data_sets[2][1]);
@@ -314,10 +314,10 @@
   ASSERT_EQ(1UL, _response.data_sets.size());
   ASSERT_EQ(SAMPLE_COUNT, _response.data_sets[0].size());
   // Check the samples themselves.
-  EXPECT_EQ(278350ULL, _response.data_sets[0][0]);
-  EXPECT_EQ(701030ULL, _response.data_sets[0][1]);
-  EXPECT_EQ(288659ULL, _response.data_sets[0][2]);
-  EXPECT_EQ(41237ULL, _response.data_sets[0][3]);
+  EXPECT_EQ(123711ULL, _response.data_sets[0][0]);
+  EXPECT_EQ(773195ULL, _response.data_sets[0][1]);
+  EXPECT_EQ(360824ULL, _response.data_sets[0][2]);
+  EXPECT_EQ(51546ULL, _response.data_sets[0][3]);
   EXPECT_EQ(154639ULL, _response.data_sets[0][4]);
 }
 
@@ -341,9 +341,9 @@
   ASSERT_EQ(1UL, _response.data_sets.size());
   ASSERT_EQ(SAMPLE_COUNT, _response.data_sets[0].size());
   // Check the samples themselves.
-  EXPECT_EQ(46ULL, _response.data_sets[0][0]);
-  EXPECT_EQ(41ULL, _response.data_sets[0][1]);
-  EXPECT_EQ(38ULL, _response.data_sets[0][2]);
+  EXPECT_EQ(47ULL, _response.data_sets[0][0]);
+  EXPECT_EQ(44ULL, _response.data_sets[0][1]);
+  EXPECT_EQ(42ULL, _response.data_sets[0][2]);
   EXPECT_EQ(20ULL, _response.data_sets[0][3]);
   EXPECT_EQ(13ULL, _response.data_sets[0][4]);
 }
@@ -370,8 +370,8 @@
   // Check the samples themselves.
   EXPECT_EQ(3ULL, _response.data_sets[0][0]);
   EXPECT_EQ(100ULL, _response.data_sets[0][1]);
-  EXPECT_EQ(12ULL, _response.data_sets[0][2]);
-  EXPECT_EQ(3ULL, _response.data_sets[0][3]);
+  EXPECT_EQ(30ULL, _response.data_sets[0][2]);
+  EXPECT_EQ(5ULL, _response.data_sets[0][3]);
   EXPECT_EQ(3ULL, _response.data_sets[0][4]);
 }
 
@@ -407,10 +407,10 @@
   ASSERT_EQ(1UL, _response.data_sets.size());
   ASSERT_EQ(SAMPLE_COUNT, _response.data_sets[0].size());
   // Check the samples themselves.
-  EXPECT_EQ(59ULL, _response.data_sets[0][0]);
-  EXPECT_EQ(97ULL, _response.data_sets[0][9]);
-  EXPECT_EQ(26ULL, _response.data_sets[0][19]);
-  EXPECT_EQ(33ULL, _response.data_sets[0][29]);
+  EXPECT_EQ(55ULL, _response.data_sets[0][0]);
+  EXPECT_EQ(99ULL, _response.data_sets[0][9]);
+  EXPECT_EQ(29ULL, _response.data_sets[0][19]);
+  EXPECT_EQ(29ULL, _response.data_sets[0][29]);
   EXPECT_EQ(99ULL, _response.data_sets[0][39]);
 }