diff --git a/test/cpp/qps/client.cc b/test/cpp/qps/client.cc
index 7c9763a..827c1ec 100644
--- a/test/cpp/qps/client.cc
+++ b/test/cpp/qps/client.cc
@@ -53,53 +53,112 @@
 #include <grpc++/server_builder.h>
 #include "test/core/util/grpc_profiler.h"
 #include "test/cpp/util/create_test_channel.h"
+#include "test/cpp/qps/client.h"
 #include "test/cpp/qps/qpstest.pb.h"
+#include "test/cpp/qps/histogram.h"
 #include "test/cpp/qps/timer.h"
 
-DEFINE_int32(driver_port, 0, "Client driver port.");
+namespace grpc {
+namespace testing {
 
-using grpc::ChannelInterface;
-using grpc::CreateTestChannel;
-using grpc::ServerBuilder;
-using grpc::ServerContext;
-using grpc::Status;
-using grpc::testing::ClientArgs;
-using grpc::testing::ClientConfig;
-using grpc::testing::ClientResult;
-using grpc::testing::QpsClient;
-using grpc::testing::SimpleRequest;
-using grpc::testing::SimpleResponse;
-using grpc::testing::StatsRequest;
-using grpc::testing::TestService;
+class SynchronousClient GRPC_FINAL : public Client {
+ public:
+  SynchronousClient(const ClientConfig& config) : timer_(new Timer) {
+    for (int i = 0; i < config.client_channels(); i++) {
+      channels_.push_back(ClientChannelInfo(config.server_targets(i % config.server_targets_size()), config));
+      auto* stub = channels_.back().get_stub();
+      for (int j = 0; j < config.outstanding_rpcs_per_channel(); j++) {
+        threads_.emplace_back(new Thread(stub, config));
+      }
+    }
+  }
 
-// In some distros, gflags is in the namespace google, and in some others,
-// in gflags. This hack is enabling us to find both.
-namespace google { }
-namespace gflags { }
-using namespace google;
-using namespace gflags;
+  ClientStats Mark() {
+    Histogram latencies;
+    std::vector<Histogram> to_merge(threads_.size());
+    for (size_t i = 0; i < threads_.size(); i++) {
+      threads_[i]->BeginSwap(&to_merge[i]);
+    }
+    std::unique_ptr<Timer> timer(new Timer);
+    timer_.swap(timer);
+    for (size_t i = 0; i < threads_.size(); i++) {
+      threads_[i]->EndSwap();
+      latencies.Merge(&to_merge[i]);
+    }
 
-static double now() {
-  gpr_timespec tv = gpr_now();
-  return 1e9 * tv.tv_sec + tv.tv_nsec;
-}
+    auto timer_result = timer->Mark();
 
-static bool got_sigint = false;
+    ClientStats stats;
+    auto* l = stats.mutable_latencies();
+    l->set_l_50(latencies.Percentile(50));
+    l->set_l_90(latencies.Percentile(90));
+    l->set_l_99(latencies.Percentile(99));
+    l->set_l_999(latencies.Percentile(99.9));
+    stats.set_num_rpcs(latencies.Count());
+    stats.set_time_elapsed(timer_result.wall);
+    stats.set_time_system(timer_result.system);
+    stats.set_time_user(timer_result.user);
+    return stats;
+  }
 
-static void sigint_handler(int x) { got_sigint = 1; }
+ private:
+  class Thread {
+   public:
+    Thread(TestService::Stub* stub, const ClientConfig& config) : stub_(stub), config_(config), done_(false), new_(nullptr), impl_([this]() {
+      SimpleRequest request;
+      SimpleResponse response;
+      request.set_response_type(
+          grpc::testing::PayloadType::COMPRESSABLE);
+      request.set_response_size(config_.payload_size());
+      for (;;) {
+        {
+          std::lock_guard<std::mutex> g(mu_);
+          if (done_) return;
+          if (new_) {
+            new_->Swap(&histogram_);
+            new_ = nullptr;
+            cv_.notify_one();
+          }
+        }
+        double start = Timer::Now();
+        grpc::ClientContext context;
+        grpc::Status s =
+            stub_->UnaryCall(&context, request, &response);
+        histogram_.Add((Timer::Now() - start) * 1e9);
+      }
+    }) {}
 
-ClientResult RunTest(const ClientArgs& args) {
-  const auto& config = args.config();
+    ~Thread() {
+      {
+        std::lock_guard<std::mutex> g(mu_);
+        done_ = true;
+      }
+      impl_.join();
+    }
 
-  gpr_log(GPR_INFO,
-          "QPS test with parameters\n"
-          "enable_ssl = %d\n"
-          "client_channels = %d\n"
-          "client_threads = %d\n"
-          "num_rpcs = %d\n"
-          "payload_size = %d\n",
-          config.enable_ssl(), config.client_channels(), config.client_threads(), config.num_rpcs(),
-          config.payload_size());
+    void BeginSwap(Histogram* n) {
+      std::lock_guard<std::mutex> g(mu_);
+      new_ = n;
+    }
+
+    void EndSwap() {
+      std::unique_lock<std::mutex> g(mu_);
+      cv_.wait(g, [this]() { return new_ == nullptr; });
+    }
+
+   private:
+    Thread(const Thread&);
+    Thread& operator=(const Thread&);
+
+    TestService::Stub* stub_;
+    ClientConfig config_;
+    std::mutex mu_;
+    std::condition_variable cv_;
+    bool done_;
+    Histogram *new_;
+    Histogram histogram_;
+    std::thread impl_;
+  };
 
   class ClientChannelInfo {
    public:
@@ -113,133 +172,14 @@
     std::shared_ptr<ChannelInterface> channel_;
     std::unique_ptr<TestService::Stub> stub_;
   };
-
-  std::vector<ClientChannelInfo> channels;
-  for (int i = 0; i < config.client_channels(); i++) {
-    channels.push_back(ClientChannelInfo(args.server_targets(i % args.server_targets_size()), config));
-  }
-
-  std::vector<std::thread> threads;  // Will add threads when ready to execute
-  std::vector< ::gpr_histogram *> thread_stats(config.client_threads());
-
-  grpc::ClientContext context_stats_begin;
-
-  grpc_profiler_start("qps_client.prof");
-
-  Timer timer;
-
-  for (int i = 0; i < config.client_threads(); i++) {
-    gpr_histogram *hist = gpr_histogram_create(0.01, 60e9);
-    GPR_ASSERT(hist != NULL);
-    thread_stats[i] = hist;
-
-    threads.push_back(
-        std::thread([hist, config, &channels](int channel_num) {
-                      SimpleRequest request;
-                      SimpleResponse response;
-                      request.set_response_type(
-                          grpc::testing::PayloadType::COMPRESSABLE);
-                      request.set_response_size(config.payload_size());
-
-                      for (int j = 0; j < config.num_rpcs(); j++) {
-                        TestService::Stub *stub =
-                            channels[channel_num].get_stub();
-                        double start = now();
-                        grpc::ClientContext context;
-                        grpc::Status s =
-                            stub->UnaryCall(&context, request, &response);
-                        gpr_histogram_add(hist, now() - start);
-
-                        GPR_ASSERT((s.code() == grpc::StatusCode::OK) &&
-                                   (response.payload().type() ==
-                                    grpc::testing::PayloadType::COMPRESSABLE) &&
-                                   (response.payload().body().length() ==
-                                    static_cast<size_t>(config.payload_size())));
-
-                        // Now do runtime round-robin assignment of the next
-                        // channel number
-                        channel_num += config.client_threads();
-                        channel_num %= config.client_channels();
-                      }
-                    },
-                    i % config.client_channels()));
-  }
-
-  for (auto &t : threads) {
-    t.join();
-  }
-
-  auto timer_result = timer.Mark();
-
-  grpc_profiler_stop();
-
-  gpr_histogram *hist = gpr_histogram_create(0.01, 60e9);
-  GPR_ASSERT(hist != NULL);
-
-  for (int i = 0; i < config.client_threads(); i++) {
-    gpr_histogram *h = thread_stats[i];
-    gpr_log(GPR_INFO, "latency at thread %d (50/90/95/99/99.9): %f/%f/%f/%f/%f",
-            i, gpr_histogram_percentile(h, 50), gpr_histogram_percentile(h, 90),
-            gpr_histogram_percentile(h, 95), gpr_histogram_percentile(h, 99),
-            gpr_histogram_percentile(h, 99.9));
-    gpr_histogram_merge(hist, h);
-    gpr_histogram_destroy(h);
-  }
-
-  ClientResult result;
-  auto* latencies = result.mutable_latencies();
-  latencies->set_l_50(gpr_histogram_percentile(hist, 50));
-  latencies->set_l_90(gpr_histogram_percentile(hist, 90));
-  latencies->set_l_99(gpr_histogram_percentile(hist, 99));
-  latencies->set_l_999(gpr_histogram_percentile(hist, 99.9));
-  result.set_num_rpcs(config.client_threads() * config.num_rpcs());
-  result.set_time_elapsed(timer_result.wall);
-  result.set_time_system(timer_result.system);
-  result.set_time_user(timer_result.user);
-
-  gpr_histogram_destroy(hist);
-
-  return result;
-}
-
-class ClientImpl final : public QpsClient::Service {
- public:
-  Status RunTest(ServerContext* ctx, const ClientArgs* args, ClientResult* result) override {
-    *result = ::RunTest(*args);
-    return Status::OK;
-  }
-
- private:
-  std::mutex client_mu_;
+  std::vector<ClientChannelInfo> channels_;
+  std::vector<std::unique_ptr<Thread>> threads_;
+  std::unique_ptr<Timer> timer_;
 };
 
-static void RunServer() {
-  char* server_address = NULL;
-  gpr_join_host_port(&server_address, "::", FLAGS_driver_port);
-
-  ClientImpl service;
-
-  ServerBuilder builder;
-  builder.AddPort(server_address);
-  builder.RegisterService(&service);
-
-  gpr_free(server_address);
-
-  auto server = builder.BuildAndStart();
-
-  while (!got_sigint) {
-    std::this_thread::sleep_for(std::chrono::seconds(5));
-  }
+std::unique_ptr<Client> CreateSynchronousClient(const ClientConfig& config) {
+  return std::unique_ptr<Client>(new SynchronousClient(config));
 }
 
-int main(int argc, char **argv) {
-  signal(SIGINT, sigint_handler);
-
-  grpc_init();
-  ParseCommandLineFlags(&argc, &argv, true);
-
-  RunServer();
-
-  grpc_shutdown();
-  return 0;
-}
+}  // namespace testing
+}  // namespace grpc
diff --git a/test/cpp/qps/client.h b/test/cpp/qps/client.h
index ab34970..97701d3 100644
--- a/test/cpp/qps/client.h
+++ b/test/cpp/qps/client.h
@@ -42,6 +42,8 @@
 class Client {
  public:
   virtual ~Client() {}
+
+  virtual ClientStats Mark() = 0;
 };
 
 std::unique_ptr<Client> CreateSynchronousClient(const ClientConfig& args);
diff --git a/test/cpp/qps/driver.cc b/test/cpp/qps/driver.cc
index a54aad5..c090d03 100644
--- a/test/cpp/qps/driver.cc
+++ b/test/cpp/qps/driver.cc
@@ -48,21 +48,9 @@
 using std::thread;
 using std::unique_ptr;
 using std::vector;
-using grpc::string;
-using grpc::ChannelArguments;
-using grpc::ClientContext;
-using grpc::ClientReaderWriter;
-using grpc::CreateChannelDeprecated;
-using grpc::Status;
-using grpc::testing::ClientArgs;
-using grpc::testing::ClientConfig;
-using grpc::testing::ClientResult;
-using grpc::testing::Worker;
-using grpc::testing::ServerArgs;
-using grpc::testing::ServerConfig;
-using grpc::testing::ServerStatus;
 
-#if 0
+namespace grpc {
+namespace testing {
 static vector<string> get_hosts(const string& name) {
   char* env = gpr_getenv(name.c_str());
   if (!env) return vector<string>();
@@ -70,119 +58,139 @@
   vector<string> out;
   char* p = env;
   for (;;) {
-  	char* comma = strchr(p, ',');
-  	if (comma) {
-  	  out.emplace_back(p, comma);
-  	  p = comma + 1;
-  	} else {
-  	  out.emplace_back(p);
-  	  gpr_free(env);
-  	  return out;
-  	}
+    char* comma = strchr(p, ',');
+    if (comma) {
+      out.emplace_back(p, comma);
+      p = comma + 1;
+    } else {
+      out.emplace_back(p);
+      gpr_free(env);
+      return out;
+    }
   }
 }
 
-void RunScenario(const ClientConfig& client_config, size_t num_clients,
+void RunScenario(const ClientConfig& initial_client_config, size_t num_clients,
                  const ServerConfig& server_config, size_t num_servers) {
   // ClientContext allocator (all are destroyed at scope exit)
   list<ClientContext> contexts;
   auto alloc_context = [&contexts]() {
-  	contexts.emplace_back();
-  	return &contexts.back();
+    contexts.emplace_back();
+    return &contexts.back();
   };
 
   // Get client, server lists
   auto workers = get_hosts("QPS_WORKERS");
+  ClientConfig client_config = initial_client_config;
 
-  GPR_ASSERT(clients.size() >= num_clients);
-  GPR_ASSERT(servers.size() >= num_servers);
+  // TODO(ctiller): support running multiple configurations, and binpack client/server pairs
+  // to available workers
+  GPR_ASSERT(workers.size() >= num_clients + num_servers);
 
   // Trim to just what we need
-  clients.resize(num_clients);
-  servers.resize(num_servers);
+  workers.resize(num_clients + num_servers);
 
   // Start servers
-  vector<unique_ptr<QpsServer::Stub>> server_stubs;
-  vector<unique_ptr<ClientReaderWriter<ServerArgs, ServerStatus>>> server_streams;
-  vector<string> server_targets;
-  for (const auto& target : servers) {
-  	server_stubs.push_back(QpsServer::NewStub(CreateChannelDeprecated(target, ChannelArguments())));
-  	auto* stub = server_stubs.back().get();
-  	ServerArgs args;
-  	*args.mutable_config() = server_config;
-  	server_streams.push_back(stub->RunServer(alloc_context()));
-  	auto* stream = server_streams.back().get();
-  	if (!stream->Write(args)) {
-  	  gpr_log(GPR_ERROR, "Failed starting server");
-  	  return;
-  	}
-  	ServerStatus init_status;
-  	if (!stream->Read(&init_status)) {
-  	  gpr_log(GPR_ERROR, "Failed starting server");
-  	  return;
-  	}
-  	char* host;
-  	char* driver_port;
-  	char* cli_target;
-  	gpr_split_host_port(target.c_str(), &host, &driver_port);
-  	gpr_join_host_port(&cli_target, host, init_status.port());
-  	server_targets.push_back(cli_target);
-  	gpr_free(host);
-  	gpr_free(driver_port);
-  	gpr_free(cli_target);
+  struct ServerData {
+    unique_ptr<Worker::Stub> stub;
+    unique_ptr<ClientReaderWriter<ServerArgs, ServerStatus>> stream;
+  };
+  vector<ServerData> servers;
+  for (size_t i = 0; i < num_servers; i++) {
+    ServerData sd;
+    sd.stub = std::move(Worker::NewStub(CreateChannelDeprecated(workers[i], ChannelArguments())));
+    ServerArgs args;
+    *args.mutable_setup() = server_config;
+    sd.stream = std::move(sd.stub->RunServer(alloc_context()));
+    GPR_ASSERT(sd.stream->Write(args));
+    ServerStatus init_status;
+    GPR_ASSERT(sd.stream->Read(&init_status));
+    char* host;
+    char* driver_port;
+    char* cli_target;
+    gpr_split_host_port(workers[i].c_str(), &host, &driver_port);
+    gpr_join_host_port(&cli_target, host, init_status.port());
+    client_config.add_server_targets(cli_target);
+    gpr_free(host);
+    gpr_free(driver_port);
+    gpr_free(cli_target);
+
+    servers.push_back(std::move(sd));
   }
 
   // Start clients
-  class Client {
-   public:
-   	Client(ClientContext* ctx, const string& target, const ClientArgs& args)
-   	  : thread_([ctx, target, args, this]() {
-   	  	auto stub = QpsClient::NewStub(CreateChannelDeprecated(target, ChannelArguments()));
-   	  	status_ = stub->RunTest(ctx, args, &result_);
-   	  }) {}
-
-   	~Client() { join(); }
-
-   	void join() { if (!joined_) { thread_.join(); joined_ = true; } }
-
-   	const Status& status() const { return status_; }
-   	const ClientResult& result() const { return result_; }
-
-   private:
-   	bool joined_ = false;
-   	Status status_;
-   	ClientResult result_;
-   	thread thread_;
+  struct ClientData {
+    unique_ptr<Worker::Stub> stub;
+    unique_ptr<ClientReaderWriter<ClientArgs, ClientStatus>> stream;
   };
-  list<Client> running_clients;
-  size_t svr_idx = 0;
-  for (const auto& target : clients) {
-  	ClientArgs args;
-  	*args.mutable_config() = client_config;
-  	for (size_t i = 0; i < num_servers; i++) {
-  	  args.add_server_targets(server_targets[svr_idx]);
-  	  svr_idx = (svr_idx + 1) % num_servers;
-  	}
+  vector<ClientData> clients;
+  for (size_t i = 0; i < num_clients; i++) {
+    ClientData cd;
+    cd.stub = std::move(Worker::NewStub(CreateChannelDeprecated(workers[i + num_servers], ChannelArguments())));
+    ClientArgs args;
+    *args.mutable_setup() = client_config;
+    cd.stream = std::move(cd.stub->RunTest(alloc_context()));
+    GPR_ASSERT(cd.stream->Write(args));
+    ClientStatus init_status;
+    GPR_ASSERT(cd.stream->Read(&init_status));
 
-  	running_clients.emplace_back(alloc_context(), target, args);
+    clients.push_back(std::move(cd));
   }
 
-  // Finish clients
-  for (auto& client : running_clients) {
-  	client.join();
-  	if (!client.status().IsOk()) {
-  	  gpr_log(GPR_ERROR, "Client failed");
-  	  return;
-  	}
+  // Let everything warmup
+  gpr_log(GPR_INFO, "Warming up");
+  gpr_timespec start = gpr_now();
+  gpr_sleep_until(gpr_time_add(start, gpr_time_from_seconds(5)));
+
+  // Start a run
+  gpr_log(GPR_INFO, "Starting");
+  ServerArgs server_mark;
+  server_mark.mutable_mark();
+  ClientArgs client_mark;
+  client_mark.mutable_mark();
+  for (auto& server : servers) {
+    GPR_ASSERT(server.stream->Write(server_mark));
+  }
+  for (auto& client : clients) {
+    GPR_ASSERT(client.stream->Write(client_mark));
+  }
+  ServerStatus server_status;
+  ClientStatus client_status;
+  for (auto& server : servers) {
+    GPR_ASSERT(server.stream->Read(&server_status));
+  }
+  for (auto& client : clients) {
+    GPR_ASSERT(client.stream->Read(&client_status));
   }
 
-  // Finish servers
-  for (auto& stream : server_streams) {
-  	ServerStatus final_status;
-  	ServerStatus dummy;
-  	if (!stream->WritesDone() || !stream->Read(&final_status) || stream->Read(&dummy) || !stream->Finish().IsOk()) {
-  	  gpr_log(GPR_ERROR, "Server protocol error");
-  	}
+  // Wait some time
+  gpr_log(GPR_INFO, "Running");
+  gpr_sleep_until(gpr_time_add(start, gpr_time_from_seconds(15)));
+
+  // Finish a run
+  gpr_log(GPR_INFO, "Finishing");
+  for (auto& server : servers) {
+    GPR_ASSERT(server.stream->Write(server_mark));
+  }
+  for (auto& client : clients) {
+    GPR_ASSERT(client.stream->Write(client_mark));
+  }
+  for (auto& server : servers) {
+    GPR_ASSERT(server.stream->Read(&server_status));
+  }
+  for (auto& client : clients) {
+    GPR_ASSERT(client.stream->Read(&client_status));
+  }
+
+  for (auto& client : clients) {
+    GPR_ASSERT(client.stream->WritesDone());
+    GPR_ASSERT(client.stream->Finish().IsOk());
+  }
+  for (auto& server : servers) {
+    GPR_ASSERT(server.stream->WritesDone());
+    GPR_ASSERT(server.stream->Finish().IsOk());
   }
 }
-#endif
\ No newline at end of file
+
+}
+}
diff --git a/test/cpp/qps/driver.h b/test/cpp/qps/driver.h
index 8ac9d2f..5c548bb 100644
--- a/test/cpp/qps/driver.h
+++ b/test/cpp/qps/driver.h
@@ -36,7 +36,11 @@
 
 #include "test/cpp/qps/qpstest.pb.h"
 
+namespace grpc {
+namespace testing {
 void RunScenario(const grpc::testing::ClientConfig& client_config, size_t num_clients,
                  const grpc::testing::ServerConfig& server_config, size_t num_servers);
+}
+}
 
 #endif
diff --git a/test/cpp/qps/histogram.h b/test/cpp/qps/histogram.h
new file mode 100644
index 0000000..b8282a4
--- /dev/null
+++ b/test/cpp/qps/histogram.h
@@ -0,0 +1,63 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef TEST_QPS_HISTOGRAM_H
+#define TEST_QPS_HISTOGRAM_H
+
+#include <grpc/support/histogram.h>
+
+namespace grpc {
+namespace testing {
+
+class Histogram {
+ public:
+  Histogram() : impl_(gpr_histogram_create(0.01, 60e9)) {}
+  ~Histogram() { gpr_histogram_destroy(impl_); }
+
+  void Merge(Histogram* h) { gpr_histogram_merge(impl_, h->impl_); }
+  void Add(double value) { gpr_histogram_add(impl_, value); }
+  double Percentile(double pctile) { return gpr_histogram_percentile(impl_, pctile); }
+  double Count() { return gpr_histogram_count(impl_); }
+  void Swap(Histogram* other) { std::swap(impl_, other->impl_); }
+
+ private:
+  Histogram(const Histogram&);
+  Histogram& operator=(const Histogram&);
+
+  gpr_histogram* impl_;
+};
+
+}
+}
+
+#endif  /* TEST_QPS_HISTOGRAM_H */
diff --git a/test/cpp/qps/qps_driver.cc b/test/cpp/qps/qps_driver.cc
index 88b9d37..cbe0b85 100644
--- a/test/cpp/qps/qps_driver.cc
+++ b/test/cpp/qps/qps_driver.cc
@@ -32,6 +32,7 @@
  */
 
 #include <gflags/gflags.h>
+#include <grpc/support/log.h>
 
 #include "test/cpp/qps/driver.h"
 
@@ -43,15 +44,18 @@
 
 // Server config
 DEFINE_int32(server_threads, 1, "Number of server threads");
+DEFINE_string(server_type, "SYNCHRONOUS_SERVER", "Server type");
 
 // Client config
-DEFINE_int32(client_threads, 1, "Number of client threads");
+DEFINE_int32(outstanding_rpcs_per_channel, 1, "Number of outstanding rpcs per channel");
 DEFINE_int32(client_channels, 1, "Number of client channels");
-DEFINE_int32(num_rpcs, 10000, "Number of rpcs per client thread");
 DEFINE_int32(payload_size, 1, "Payload size");
+DEFINE_string(client_type, "SYNCHRONOUS_CLIENT", "Client type");
 
 using grpc::testing::ClientConfig;
 using grpc::testing::ServerConfig;
+using grpc::testing::ClientType;
+using grpc::testing::ServerType;
 
 // In some distros, gflags is in the namespace google, and in some others,
 // in gflags. This hack is enabling us to find both.
@@ -64,14 +68,20 @@
   grpc_init();
   ParseCommandLineFlags(&argc, &argv, true);
 
+  ClientType client_type;
+  ServerType server_type;
+  GPR_ASSERT(ClientType_Parse(FLAGS_client_type, &client_type));
+  GPR_ASSERT(ServerType_Parse(FLAGS_server_type, &server_type));
+
   ClientConfig client_config;
+  client_config.set_client_type(client_type);
   client_config.set_enable_ssl(FLAGS_enable_ssl);
-  client_config.set_client_threads(FLAGS_client_threads);
+  client_config.set_outstanding_rpcs_per_channel(FLAGS_outstanding_rpcs_per_channel);
   client_config.set_client_channels(FLAGS_client_channels);
-  client_config.set_num_rpcs(FLAGS_num_rpcs);
   client_config.set_payload_size(FLAGS_payload_size);
 
   ServerConfig server_config;
+  server_config.set_server_type(server_type);
   server_config.set_threads(FLAGS_server_threads);
   server_config.set_enable_ssl(FLAGS_enable_ssl);
 
diff --git a/test/cpp/qps/qpstest.proto b/test/cpp/qps/qpstest.proto
index 52d7957..39d44cd 100644
--- a/test/cpp/qps/qpstest.proto
+++ b/test/cpp/qps/qpstest.proto
@@ -89,30 +89,21 @@
   repeated string server_targets = 1;
   required ClientType client_type = 2;
   required bool enable_ssl = 3;
-  required int32 client_threads = 4;
-  // We have a configurable number of channels for sending RPCs.
-  // RPCs are sent round-robin on the available channels by the
-  // various threads. Interesting cases are 1 global channel or
-  // 1 per-thread channel, but we can support any number.
-  // The channels are assigned round-robin on an RPC by RPC basis
-  // rather than just at initialization time in order to also measure the
-  // impact of cache thrashing caused by channel changes. This is an issue
-  // if you are not in one of the above "interesting cases"
+  required int32 outstanding_rpcs_per_channel = 4;
   required int32 client_channels = 5;
-  required int32 num_rpcs = 6;
-  required int32 payload_size = 7;
+  required int32 payload_size = 6;
 }
 
-message ClientStart {}
+message Mark {}
 
 message ClientArgs {
   oneof argtype {
     ClientConfig setup = 1;
-    ClientStart start = 2;
+    Mark mark = 2;
   }
 }
 
-message ClientResult {
+message ClientStats {
   required Latencies latencies = 1;
   required int32 num_rpcs = 2;
   required double time_elapsed = 3;
@@ -121,7 +112,7 @@
 }
 
 message ClientStatus {
-  optional ClientResult result = 1;
+  optional ClientStats stats = 1;
 }
 
 message ServerConfig {
@@ -131,7 +122,10 @@
 }
 
 message ServerArgs {
-  required ServerConfig config = 1;
+  oneof argtype {
+    ServerConfig setup = 1;
+    Mark mark = 2;
+  }
 }
 
 message ServerStatus {
diff --git a/test/cpp/qps/server.cc b/test/cpp/qps/server.cc
index 75425c9..ebe06c1 100644
--- a/test/cpp/qps/server.cc
+++ b/test/cpp/qps/server.cc
@@ -48,42 +48,14 @@
 #include "src/cpp/server/thread_pool.h"
 #include "test/core/util/grpc_profiler.h"
 #include "test/cpp/qps/qpstest.pb.h"
+#include "test/cpp/qps/server.h"
 #include "test/cpp/qps/timer.h"
 
 #include <grpc/grpc.h>
 #include <grpc/support/log.h>
 
-DEFINE_int32(port, 0, "Server port.");
-DEFINE_int32(driver_port, 0, "Server driver port.");
-
-using grpc::Server;
-using grpc::ServerBuilder;
-using grpc::ServerContext;
-using grpc::ServerReaderWriter;
-using grpc::ThreadPool;
-using grpc::testing::Payload;
-using grpc::testing::PayloadType;
-using grpc::testing::ServerStats;
-using grpc::testing::SimpleRequest;
-using grpc::testing::SimpleResponse;
-using grpc::testing::StatsRequest;
-using grpc::testing::TestService;
-using grpc::testing::QpsServer;
-using grpc::testing::ServerArgs;
-using grpc::testing::ServerStats;
-using grpc::testing::ServerStatus;
-using grpc::Status;
-
-// In some distros, gflags is in the namespace google, and in some others,
-// in gflags. This hack is enabling us to find both.
-namespace google { }
-namespace gflags { }
-using namespace google;
-using namespace gflags;
-
-static bool got_sigint = false;
-
-static void sigint_handler(int x) { got_sigint = 1; }
+namespace grpc {
+namespace testing {
 
 static bool SetPayload(PayloadType type, int size, Payload* payload) {
   PayloadType response_type = type;
@@ -97,8 +69,6 @@
   return true;
 }
 
-namespace {
-
 class TestServiceImpl GRPC_FINAL : public TestService::Service {
  public:
   Status UnaryCall(ServerContext* context, const SimpleRequest* request,
@@ -113,88 +83,46 @@
   }
 };
 
-}  // namespace
-
-class ServerImpl : public QpsServer::Service {
+class SynchronousServer GRPC_FINAL : public grpc::testing::Server {
  public:
-  Status RunServer(ServerContext* ctx, ServerReaderWriter<ServerStatus, ServerArgs>* stream) {
-    ServerArgs args;
-    if (!stream->Read(&args)) return Status::OK;
+  SynchronousServer(const ServerConfig& config, int port) : thread_pool_(config.threads()), impl_(MakeImpl(port)), timer_(new Timer) {}
 
-    std::lock_guard<std::mutex> lock(server_mu_);
+  ServerStats Mark() GRPC_OVERRIDE {
+    std::unique_ptr<Timer> timer(new Timer);
+    timer.swap(timer_);
 
-    char* server_address = NULL;
-    gpr_join_host_port(&server_address, "::", FLAGS_port);
+    auto timer_result = timer->Mark();
 
-    TestServiceImpl service;
-
-    ServerBuilder builder;
-    builder.AddPort(server_address);
-    builder.RegisterService(&service);
-
-    std::unique_ptr<ThreadPool> pool(new ThreadPool(args.config().threads()));
-    builder.SetThreadPool(pool.get());
-
-    auto server = builder.BuildAndStart();
-    gpr_log(GPR_INFO, "Server listening on %s\n", server_address);
-
-    gpr_free(server_address);
-
-    ServerStatus status;
-    status.set_port(FLAGS_port);
-    if (!stream->Write(status)) return Status(grpc::UNKNOWN);
-
-    grpc_profiler_start("qps_server.prof");
-    Timer timer;
-
-    if (stream->Read(&args)) {
-      gpr_log(GPR_ERROR, "Got a server request, but not expecting one");
-      return Status(grpc::UNKNOWN);
-    }
-
-    auto timer_result = timer.Mark();
-    grpc_profiler_stop();
-
-    auto* stats = status.mutable_stats();
-    stats->set_time_elapsed(timer_result.wall);
-    stats->set_time_system(timer_result.system);
-    stats->set_time_user(timer_result.user);
-    stream->Write(status);
-    return Status::OK;
+    ServerStats stats;
+    stats.set_time_elapsed(timer_result.wall);
+    stats.set_time_system(timer_result.system);
+    stats.set_time_user(timer_result.user);
+    return stats;
   }
 
  private:
-  std::mutex server_mu_;
+  std::unique_ptr<grpc::Server> MakeImpl(int port) {
+    ServerBuilder builder;
+
+    char* server_address = NULL;
+    gpr_join_host_port(&server_address, "::", port);
+    builder.AddPort(server_address);
+    gpr_free(server_address);
+
+    builder.RegisterService(&service_);
+
+    return builder.BuildAndStart();
+  }
+
+  TestServiceImpl service_;
+  ThreadPool thread_pool_;
+  std::unique_ptr<grpc::Server> impl_;
+  std::unique_ptr<Timer> timer_;
 };
 
-static void RunServer() {
-  char* server_address = NULL;
-  gpr_join_host_port(&server_address, "::", FLAGS_driver_port);
-
-  ServerImpl service;
-
-  ServerBuilder builder;
-  builder.AddPort(server_address);
-  builder.RegisterService(&service);
-
-  gpr_free(server_address);
-
-  auto server = builder.BuildAndStart();
-
-  while (!got_sigint) {
-    sleep(5);
-  }
+std::unique_ptr<grpc::testing::Server> CreateSynchronousServer(const ServerConfig& config, int port) {
+  return std::unique_ptr<Server>(new SynchronousServer(config, port));
 }
 
-int main(int argc, char** argv) {
-  signal(SIGINT, sigint_handler);
-
-  grpc_init();
-  ParseCommandLineFlags(&argc, &argv, true);
-
-  GPR_ASSERT(FLAGS_port != 0);
-  RunServer();
-
-  grpc_shutdown();
-  return 0;
-}
+}  // namespace testing
+}  // namespace grpc
diff --git a/test/cpp/qps/server.h b/test/cpp/qps/server.h
index 25c15e4..35d1aed 100644
--- a/test/cpp/qps/server.h
+++ b/test/cpp/qps/server.h
@@ -42,6 +42,8 @@
 class Server {
  public:
   virtual ~Server() {}
+
+  virtual ServerStats Mark() = 0;
 };
 
 std::unique_ptr<Server> CreateSynchronousServer(const ServerConfig& config, int port);
diff --git a/test/cpp/qps/single_run_localhost.sh b/test/cpp/qps/single_run_localhost.sh
index 310a082..2f60b4e 100755
--- a/test/cpp/qps/single_run_localhost.sh
+++ b/test/cpp/qps/single_run_localhost.sh
@@ -6,25 +6,23 @@
 
 cd $(dirname $0)/../../..
 
-killall qps_server qps_client || true
+killall qps_worker || true
 
 config=opt
 
 NUMCPUS=`python2.7 -c 'import multiprocessing; print multiprocessing.cpu_count()'`
 
-make CONFIG=$config qps_client qps_server qps_driver -j$NUMCPUS
+make CONFIG=$config qps_worker qps_driver -j$NUMCPUS
 
-bins/$config/qps_server -driver_port 10000 -port 10002 &
-SERVER_PID=$!
-bins/$config/qps_client -driver_port 10001 &
-CLIENT_PID=$!
+bins/$config/qps_worker -driver_port 10000 -server_port 10001 &
+PID1=$!
+bins/$config/qps_worker -driver_port 10010 -server_port 10011 &
+PID2=$!
 
-export QPS_SERVERS=localhost:10000
-export QPS_CLIENTS=localhost:10001
+export QPS_WORKERS="localhost:10000,localhost:10010"
 
 bins/$config/qps_driver $*
 
-kill -2 $CLIENT_PID
-kill -2 $SERVER_PID
+kill -2 $PID1 $PID2
 wait
 
diff --git a/test/cpp/qps/timer.cc b/test/cpp/qps/timer.cc
index 5a5be97..3c13420 100644
--- a/test/cpp/qps/timer.cc
+++ b/test/cpp/qps/timer.cc
@@ -35,9 +35,15 @@
 
 #include <sys/time.h>
 #include <sys/resource.h>
+#include <grpc/support/time.h>
 
 Timer::Timer() : start_(Sample()) {}
 
+double Timer::Now() {
+  auto ts = gpr_now();
+  return ts.tv_sec + 1e-9 * ts.tv_nsec;
+}
+
 static double time_double(struct timeval* tv) {
   return tv->tv_sec + 1e-6 * tv->tv_usec;
 }
diff --git a/test/cpp/qps/timer.h b/test/cpp/qps/timer.h
index 8a229cb..1c9a006 100644
--- a/test/cpp/qps/timer.h
+++ b/test/cpp/qps/timer.h
@@ -46,6 +46,8 @@
 
   Result Mark();
 
+  static double Now();
+
  private:
   static Result Sample();
 
diff --git a/test/cpp/qps/worker.cc b/test/cpp/qps/worker.cc
index 749420b..741dfc0 100644
--- a/test/cpp/qps/worker.cc
+++ b/test/cpp/qps/worker.cc
@@ -78,7 +78,7 @@
 std::unique_ptr<Client> CreateClient(const ClientConfig& config) {
   switch (config.client_type()) {
   	case ClientType::SYNCHRONOUS_CLIENT: return CreateSynchronousClient(config);
-  	case ClientType::ASYNC_CLIENT: return CreateAsyncClient(config);
+  	case ClientType::ASYNC_CLIENT: abort(); //return CreateAsyncClient(config);
   }
   abort();
 }
@@ -86,7 +86,7 @@
 std::unique_ptr<Server> CreateServer(const ServerConfig& config) {
   switch (config.server_type()) {
   	case ServerType::SYNCHRONOUS_SERVER: return CreateSynchronousServer(config, FLAGS_server_port);
-  	case ServerType::ASYNC_SERVER: return CreateAsyncServer(config, FLAGS_server_port);
+  	case ServerType::ASYNC_SERVER: abort(); //return CreateAsyncServer(config, FLAGS_server_port);
   }
   abort();
 }
@@ -112,6 +112,17 @@
   	if (!client) {
   	  return Status(INVALID_ARGUMENT);
   	}
+    ClientStatus status;
+    if (!stream->Write(status)) {
+      return Status(UNKNOWN);
+    }
+    while (stream->Read(&args)) {
+      if (!args.has_mark()) {
+        return Status(INVALID_ARGUMENT);
+      }
+      *status.mutable_stats() = client->Mark();
+      stream->Write(status);
+    }
 
     return Status::OK;
   }
@@ -126,13 +137,25 @@
   	if (!stream->Read(&args)) {
   	  return Status(INVALID_ARGUMENT);
   	}
-  	if (!args.has_config()) {
+  	if (!args.has_setup()) {
   	  return Status(INVALID_ARGUMENT);
   	}
-  	auto server = CreateServer(args.config());
+  	auto server = CreateServer(args.setup());
   	if (!server) {
   	  return Status(INVALID_ARGUMENT);
   	}
+    ServerStatus status;
+    status.set_port(FLAGS_server_port);
+    if (!stream->Write(status)) {
+      return Status(UNKNOWN);
+    }
+    while (stream->Read(&args)) {
+      if (!args.has_mark()) {
+        return Status(INVALID_ARGUMENT);
+      }
+      *status.mutable_stats() = server->Mark();
+      stream->Write(status);
+    }
 
     return Status::OK;
   }