Add idle_cycles Perf counter

Author: cstlee

include/Homa/Perf.h

@@ -35,6 +35,9 @@ struct Stats {
     /// CPU time spent actively processing Homa messages in cycles.
     uint64_t active_cycles;
 
+    /// CPU time spent running Homa with no work to do in cycles.
+    uint64_t idle_cycles;
+
     /// Number of bytes sent by the transport.
     uint64_t tx_bytes;
 

src/Perf.h

@@ -71,6 +71,7 @@ struct Counters {
      */
     Counters()
         : active_cycles(0)
+        , idle_cycles(0)
         , tx_bytes(0)
         , rx_bytes(0)
         , tx_data_pkts(0)
@@ -102,6 +103,7 @@ struct Counters {
     void add(const Counters* other)
     {
         active_cycles.add(other->active_cycles);
+        idle_cycles.add(other->idle_cycles);
         tx_bytes.add(other->tx_bytes);
         rx_bytes.add(other->rx_bytes);
         tx_data_pkts.add(other->tx_data_pkts);
@@ -128,6 +130,7 @@ struct Counters {
     void dumpStats(Stats* stats)
     {
         stats->active_cycles = active_cycles.get();
+        stats->idle_cycles = idle_cycles.get();
         stats->tx_bytes = tx_bytes.get();
         stats->rx_bytes = rx_bytes.get();
         stats->tx_data_pkts = tx_data_pkts.get();
@@ -151,6 +154,9 @@ struct Counters {
     /// CPU time spent actively processing Homa messages in cycles.
     Stat<uint64_t> active_cycles;
 
+    /// CPU time spent running Homa with no work to do in cycles.
+    Stat<uint64_t> idle_cycles;
+
     /// Number of bytes sent by the transport.
     Stat<uint64_t> tx_bytes;
 

src/Receiver.cc

@@ -786,6 +786,8 @@ Receiver::trySendGrants()
     uint64_t elapsed_cycles = PerfUtils::Cycles::rdtsc() - start_tsc;
     if (!idle) {
         Perf::counters.active_cycles.add(elapsed_cycles);
+    } else {
+        Perf::counters.idle_cycles.add(elapsed_cycles);
     }
 }
 

src/Sender.cc

@@ -1035,6 +1035,8 @@ Sender::trySend()
     uint64_t elapsed_cycles = PerfUtils::Cycles::rdtsc() - start_tsc;
     if (!idle) {
         Perf::counters.active_cycles.add(elapsed_cycles);
+    } else {
+        Perf::counters.idle_cycles.add(elapsed_cycles);
     }
 }
 

src/TransportImpl.cc

@@ -144,6 +144,8 @@ TransportImpl::processPackets()
     uint64_t elapsed_cycles = PerfUtils::Cycles::rdtsc() - start_tsc;
     if (!idle) {
         Perf::counters.active_cycles.add(elapsed_cycles);
+    } else {
+        Perf::counters.idle_cycles.add(elapsed_cycles);
     }
 }