Add --skip option: By default, mutilate tries to maintain a long-term QPS average by issuing requests as quickly as possible until it catches up with where it 'ought' to be. If you give the --skip option, it will instead just skip sending requests that are already late.

AgentStats.h

@@ -6,6 +6,7 @@ class AgentStats {
 public:
   uint64_t rx_bytes, tx_bytes;
   uint64_t gets, sets, get_misses;
+  uint64_t skips;
 
   double start, stop;
 };

Connection.cc

@@ -256,8 +256,17 @@ void Connection::drive_write_machine(double now) {
       issue_something(now);
       stats.log_op(op_queue.size());
 
+      if (args.skip_given && op_queue.size() >= (size_t) options.depth) {
         next_time += iagen->generate();
 
+        while (next_time < now) {
+          stats.skips++;
+          next_time += iagen->generate();
+        }
+      } else {
+        next_time += iagen->generate();
+      }
+
       break;
 
     case WAITING_FOR_TIME:

ConnectionStats.h

@@ -29,7 +29,7 @@ class ConnectionStats {
    get_sampler(200), set_sampler(200), op_sampler(100),
 #endif
    rx_bytes(0), tx_bytes(0), gets(0), sets(0),
-   get_misses(0), sampling(_sampling) {}
+   get_misses(0), skips(0), sampling(_sampling) {}
 
 #ifdef USE_ADAPTIVE_SAMPLER
   AdaptiveSampler<Operation> get_sampler;
@@ -47,6 +47,7 @@ class ConnectionStats {
 
   uint64_t rx_bytes, tx_bytes;
   uint64_t gets, sets, get_misses;
+  uint64_t skips;
 
   double start, stop;
 
@@ -103,6 +104,7 @@ class ConnectionStats {
     gets += cs.gets;
     sets += cs.sets;
     get_misses += cs.get_misses;
+    skips += cs.skips;
 
     start = cs.start;
     stop = cs.stop;
@@ -114,6 +116,7 @@ class ConnectionStats {
     gets += as.gets;
     sets += as.sets;
     get_misses += as.get_misses;
+    skips += as.skips;
 
     start = as.start;
     stop = as.stop;

cmdline.ggo

@@ -40,17 +40,20 @@ By default, each thread connects to every server."
 option "iadist" i "Inter-arrival distribution (distribution).  Note: \
 The distribution will automatically be adjusted to match the QPS given \
 by --qps." string default="exponential"
+option "skip" S "Skip transmissions if previous requests are late.  This \
+harms the long-term QPS average, but reduces spikes in QPS after \
+long latency requests."
 
 option "noload" - "Skip database loading."
 option "loadonly" - "Load database and then exit."
 
 option "blocking" B "Use blocking epoll().  May increase latency."
-option "no_nodelay" D "Don't use TCP_NODELAY."
+option "no_nodelay" - "Don't use TCP_NODELAY."
 
 option "warmup" w "Warmup time before starting measurement." int
 option "wait" W "Time to wait after startup to start measurement." int
 
-option "search" S "Search for the QPS where N-order statistic < Xus.  \
+option "search" - "Search for the QPS where N-order statistic < Xus.  \
 (i.e. --search 95:1000 means find the QPS where 95% of requests are \
 faster than 1000us)." string typestr="N:X"
 option "scan" - "Scan latency across QPS rates from min to max."
@@ -65,7 +68,7 @@ option "measure_connections" C "Master client connections per server, \
 overrides --connections." int
 option "measure_qps" Q "Explicitly set master client QPS, \
 spread across threads and connections." int
-option "measure_depth" - "Set master client depth." int
+option "measure_depth" D "Set master client connection depth." int
 
 text "
 The --measure_* options aid in taking latency measurements of the

mutilate.cc

@@ -210,6 +210,7 @@ void agent() {
     as.get_misses = stats.get_misses;
     as.start = stats.start;
     as.stop = stats.stop;
+    as.skips = stats.skips;
 
     string req = s_recv(socket);
     //    V("req = %s", req.c_str());
@@ -570,16 +571,18 @@ int main(int argc, char **argv) {
 
     int total = stats.gets + stats.sets;
 
-    printf("\nTotal QPS = %.1f (%d / %.1fs)\n\n",
+    printf("\nTotal QPS = %.1f (%d / %.1fs)\n",
            total / (stats.stop - stats.start),
            total, stats.stop - stats.start);
 
     if (args.search_given && peak_qps > 0.0)
       printf("Peak QPS  = %.1f\n\n", peak_qps);
 
-    printf("Misses = %" PRIu64 " (%.1f%%)\n\n", stats.get_misses,
+    printf("Misses = %" PRIu64 " (%.1f%%)\n", stats.get_misses,
            (double) stats.get_misses/stats.gets*100);
 
+    printf("Skipped TXs = %" PRIu64 "\n\n", stats.skips);
+
     printf("RX %10" PRIu64 " bytes : %6.1f MB/s\n",
            stats.rx_bytes,
            (double) stats.rx_bytes / 1024 / 1024 / (stats.stop - stats.start));