h2load: Perform sampling for request timings to reduce memory consumption

src/h2load.cc

@@ -98,11 +98,15 @@ Config config;
 
 RequestStat::RequestStat() : data_offset(0), completed(false) {}
 
+constexpr size_t MAX_STATS = 1000000;
+
 Stats::Stats(size_t req_todo, size_t nclients)
     : req_todo(0), req_started(0), req_done(0), req_success(0),
       req_status_success(0), req_failed(0), req_error(0), req_timedout(0),
       bytes_total(0), bytes_head(0), bytes_head_decomp(0), bytes_body(0),
-      status(), req_stats(req_todo), client_stats(nclients) {}
+      status(), client_stats(nclients) {
+  req_stats.reserve(std::min(req_todo, MAX_STATS));
+}
 
 Stream::Stream() : status_success(-1) {}
 
@@ -420,9 +424,8 @@ void Client::disconnect() {
 }
 
 int Client::submit_request() {
-  auto req_stat = &worker->stats.req_stats[worker->stats.req_started++];
-
-  if (session->submit_request(req_stat) != 0) {
+  ++worker->stats.req_started;
+  if (session->submit_request() != 0) {
     return -1;
   }
 
@@ -607,8 +610,12 @@ void Client::on_status_code(int32_t stream_id, uint16_t status) {
   }
 }
 
-void Client::on_stream_close(int32_t stream_id, bool success,
-                             RequestStat *req_stat, bool final) {
+void Client::on_stream_close(int32_t stream_id, bool success, bool final) {
+  auto req_stat = get_req_stat(stream_id);
+  if (!req_stat) {
+    return;
+  }
+
   req_stat->stream_close_time = std::chrono::steady_clock::now();
   if (success) {
     req_stat->completed = true;
@@ -628,6 +635,12 @@ void Client::on_stream_close(int32_t stream_id, bool success,
     ++worker->stats.req_failed;
     ++worker->stats.req_error;
   }
+
+  if (req_stat->completed &&
+      (worker->stats.req_done % worker->request_times_sampling_step) == 0) {
+    worker->sample_req_stat(req_stat);
+  }
+
   report_progress();
   streams.erase(stream_id);
   if (req_done == req_todo) {
@@ -645,6 +658,15 @@ void Client::on_stream_close(int32_t stream_id, bool success,
   }
 }
 
+RequestStat *Client::get_req_stat(int32_t stream_id) {
+  auto it = streams.find(stream_id);
+  if (it == std::end(streams)) {
+    return nullptr;
+  }
+
+  return &(*it).second.req_stat;
+}
+
 int Client::connection_made() {
   if (ssl) {
     report_tls_info();
@@ -750,7 +772,6 @@ int Client::connection_made() {
   if (!config.timing_script) {
     auto nreq =
         std::min(req_todo - req_started, (size_t)config.max_concurrent_streams);
-
     for (; nreq > 0; --nreq) {
       if (submit_request() != 0) {
         process_request_failure();
@@ -1060,6 +1081,10 @@ Worker::Worker(uint32_t id, SSL_CTX *ssl_ctx, size_t req_todo, size_t nclients,
       clients.push_back(make_unique<Client>(next_client_id++, this, req_todo));
     }
   }
+
+  auto request_times_max_stats = std::min(req_todo, MAX_STATS);
+  request_times_sampling_step =
+      (req_todo + request_times_max_stats - 1) / request_times_max_stats;
 }
 
 Worker::~Worker() {
@@ -1088,6 +1113,11 @@ void Worker::run() {
   ev_run(loop, 0);
 }
 
+void Worker::sample_req_stat(RequestStat *req_stat) {
+  stats.req_stats.push_back(*req_stat);
+  assert(stats.req_stats.size() <= MAX_STATS);
+}
+
 namespace {
 // Returns percentage of number of samples within mean +/- sd.
 double within_sd(const std::vector<double> &samples, double mean, double sd) {
@@ -1106,12 +1136,15 @@ double within_sd(const std::vector<double> &samples, double mean, double sd) {
 namespace {
 // Computes statistics using |samples|. The min, max, mean, sd, and
 // percentage of number of samples within mean +/- sd are computed.
-SDStat compute_time_stat(const std::vector<double> &samples) {
+// If |sampling| is true, this computes sample variance.  Otherwise,
+// population variance.
+SDStat compute_time_stat(const std::vector<double> &samples,
+                         bool sampling = false) {
   if (samples.empty()) {
     return {0.0, 0.0, 0.0, 0.0, 0.0};
   }
   // standard deviation calculated using Rapid calculation method:
-  // http://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
+  // https://en.wikipedia.org/wiki/Standard_deviation#Rapid_calculation_methods
   double a = 0, q = 0;
   size_t n = 0;
   double sum = 0;
@@ -1130,7 +1163,7 @@ SDStat compute_time_stat(const std::vector<double> &samples) {
 
   assert(n > 0);
   res.mean = sum / n;
-  res.sd = sqrt(q / n);
+  res.sd = sqrt(q / (sampling && n > 1 ? n - 1 : n));
   res.within_sd = within_sd(samples, res.mean, res.sd);
 
   return res;
@@ -1140,9 +1173,13 @@ SDStat compute_time_stat(const std::vector<double> &samples) {
 namespace {
 SDStats
 process_time_stats(const std::vector<std::unique_ptr<Worker>> &workers) {
+  auto request_times_sampling = false;
   size_t nrequest_times = 0;
   for (const auto &w : workers) {
     nrequest_times += w->stats.req_stats.size();
+    if (w->request_times_sampling_step != 1) {
+      request_times_sampling = true;
+    }
   }
 
   std::vector<double> request_times;
@@ -1195,8 +1232,9 @@ process_time_stats(const std::vector<std::unique_ptr<Worker>> &workers) {
     }
   }
 
-  return {compute_time_stat(request_times), compute_time_stat(connect_times),
-          compute_time_stat(ttfb_times), compute_time_stat(rps_values)};
+  return {compute_time_stat(request_times, request_times_sampling),
+          compute_time_stat(connect_times), compute_time_stat(ttfb_times),
+          compute_time_stat(rps_values)};
 }
 } // namespace
 

src/h2load.h

@@ -226,6 +226,9 @@ struct Worker {
   // at most nreqs_rem clients get an extra request
   size_t nreqs_rem;
   size_t rate;
+  // every successful request_times_sampling_step-th request's
+  // req_stat will get sampled.
+  size_t request_times_sampling_step;
   ev_timer timeout_watcher;
   // The next client ID this worker assigns
   uint32_t next_client_id;
@@ -235,9 +238,11 @@ struct Worker {
   ~Worker();
   Worker(Worker &&o) = default;
   void run();
+  void sample_req_stat(RequestStat *req_stat);
 };
 
 struct Stream {
+  RequestStat req_stat;
   int status_success;
   Stream();
 };
@@ -318,8 +323,12 @@ struct Client {
   // |success| == true means that the request/response was exchanged
   // |successfully, but it does not mean response carried successful
   // |HTTP status code.
-  void on_stream_close(int32_t stream_id, bool success, RequestStat *req_stat,
-                       bool final = false);
+  void on_stream_close(int32_t stream_id, bool success, bool final = false);
+  // Returns RequestStat for |stream_id|.  This function must be
+  // called after on_request(stream_id), and before
+  // on_stream_close(stream_id, ...).  Otherwise, this will return
+  // nullptr.
+  RequestStat *get_req_stat(int32_t stream_id);
 
   void record_request_time(RequestStat *req_stat);
   void record_connect_start_time();

src/h2load_http1_session.cc

@@ -80,9 +80,11 @@ int htp_msg_completecb(http_parser *htp) {
   auto client = session->get_client();
 
   auto final = http_should_keep_alive(htp) == 0;
-  client->on_stream_close(session->stream_resp_counter_, true,
-                          session->req_stats_[session->stream_resp_counter_],
-                          final);
+  auto req_stat = client->get_req_stat(session->stream_resp_counter_);
+
+  assert(req_stat);
+
+  client->on_stream_close(session->stream_resp_counter_, true, final);
 
   session->stream_resp_counter_ += 2;
 
@@ -150,7 +152,7 @@ http_parser_settings htp_hooks = {
 
 void Http1Session::on_connect() { client_->signal_write(); }
 
-int Http1Session::submit_request(RequestStat *req_stat) {
+int Http1Session::submit_request() {
   auto config = client_->worker->config;
   const auto &req = config->h1reqs[client_->reqidx];
   client_->reqidx++;
@@ -159,13 +161,13 @@ int Http1Session::submit_request(RequestStat *req_stat) {
     client_->reqidx = 0;
   }
 
-  assert(req_stat);
+  client_->on_request(stream_req_counter_);
+
+  auto req_stat = client_->get_req_stat(stream_req_counter_);
+
   client_->record_request_time(req_stat);
   client_->wb.write(req.c_str(), req.size());
 
-  client_->on_request(stream_req_counter_);
-  req_stats_[stream_req_counter_] = req_stat;
-
   // increment for next request
   stream_req_counter_ += 2;
 

src/h2load_http1_session.h

@@ -38,14 +38,13 @@ public:
   Http1Session(Client *client);
   virtual ~Http1Session();
   virtual void on_connect();
-  virtual int submit_request(RequestStat *req_stat);
+  virtual int submit_request();
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();
   Client *get_client();
   int32_t stream_req_counter_;
   int32_t stream_resp_counter_;
-  std::unordered_map<int32_t, RequestStat *> req_stats_;
 
 private:
   Client *client_;

src/h2load_http2_session.cc

@@ -89,12 +89,25 @@ namespace {
 int on_stream_close_callback(nghttp2_session *session, int32_t stream_id,
                              uint32_t error_code, void *user_data) {
   auto client = static_cast<Client *>(user_data);
-  auto req_stat = static_cast<RequestStat *>(
-      nghttp2_session_get_stream_user_data(session, stream_id));
-  if (!req_stat) {
+  client->on_stream_close(stream_id, error_code == NGHTTP2_NO_ERROR);
+
+  return 0;
+}
+} // namespace
+
+namespace {
+int on_frame_not_send_callback(nghttp2_session *session,
+                               const nghttp2_frame *frame, int lib_error_code,
+                               void *user_data) {
+  if (frame->hd.type != NGHTTP2_HEADERS ||
+      frame->headers.cat != NGHTTP2_HCAT_REQUEST) {
     return 0;
   }
-  client->on_stream_close(stream_id, error_code == NGHTTP2_NO_ERROR, req_stat);
+
+  auto client = static_cast<Client *>(user_data);
+  // request was not sent.  Mark it as error.
+  client->on_stream_close(frame->hd.stream_id, false);
+
   return 0;
 }
 } // namespace
@@ -108,9 +121,7 @@ int before_frame_send_callback(nghttp2_session *session,
   }
 
   auto client = static_cast<Client *>(user_data);
-  client->on_request(frame->hd.stream_id);
-  auto req_stat = static_cast<RequestStat *>(
-      nghttp2_session_get_stream_user_data(session, frame->hd.stream_id));
+  auto req_stat = client->get_req_stat(frame->hd.stream_id);
   assert(req_stat);
   client->record_request_time(req_stat);
 
@@ -124,8 +135,7 @@ ssize_t file_read_callback(nghttp2_session *session, int32_t stream_id,
                            nghttp2_data_source *source, void *user_data) {
   auto client = static_cast<Client *>(user_data);
   auto config = client->worker->config;
-  auto req_stat = static_cast<RequestStat *>(
-      nghttp2_session_get_stream_user_data(session, stream_id));
+  auto req_stat = client->get_req_stat(stream_id);
   assert(req_stat);
   ssize_t nread;
   while ((nread = pread(config->data_fd, buf, length, req_stat->data_offset)) ==
@@ -183,6 +193,9 @@ void Http2Session::on_connect() {
   nghttp2_session_callbacks_set_on_header_callback(callbacks,
                                                    on_header_callback);
 
+  nghttp2_session_callbacks_set_on_frame_not_send_callback(
+      callbacks, on_frame_not_send_callback);
+
   nghttp2_session_callbacks_set_before_frame_send_callback(
       callbacks, before_frame_send_callback);
 
@@ -212,7 +225,7 @@ void Http2Session::on_connect() {
   client_->signal_write();
 }
 
-int Http2Session::submit_request(RequestStat *req_stat) {
+int Http2Session::submit_request() {
   if (nghttp2_session_check_request_allowed(session_) == 0) {
     return -1;
   }
@@ -228,11 +241,13 @@ int Http2Session::submit_request(RequestStat *req_stat) {
 
   auto stream_id =
       nghttp2_submit_request(session_, nullptr, nva.data(), nva.size(),
-                             config->data_fd == -1 ? nullptr : &prd, req_stat);
+                             config->data_fd == -1 ? nullptr : &prd, nullptr);
   if (stream_id < 0) {
     return -1;
   }
 
+  client_->on_request(stream_id);
+
   return 0;
 }
 

src/h2load_http2_session.h

@@ -38,7 +38,7 @@ public:
   Http2Session(Client *client);
   virtual ~Http2Session();
   virtual void on_connect();
-  virtual int submit_request(RequestStat *req_stat);
+  virtual int submit_request();
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();

src/h2load_session.h

@@ -41,7 +41,7 @@ public:
   // Called when the connection was made.
   virtual void on_connect() = 0;
   // Called when one request must be issued.
-  virtual int submit_request(RequestStat *req_stat) = 0;
+  virtual int submit_request() = 0;
   // Called when incoming bytes are available. The subclass has to
   // return the number of bytes read.
   virtual int on_read(const uint8_t *data, size_t len) = 0;

src/h2load_spdy_session.cc

@@ -48,9 +48,7 @@ void before_ctrl_send_callback(spdylay_session *session,
     return;
   }
   client->on_request(frame->syn_stream.stream_id);
-  auto req_stat =
-      static_cast<RequestStat *>(spdylay_session_get_stream_user_data(
-          session, frame->syn_stream.stream_id));
+  auto req_stat = client->get_req_stat(frame->syn_stream.stream_id);
   client->record_request_time(req_stat);
 }
 } // namespace
@@ -104,9 +102,7 @@ void on_stream_close_callback(spdylay_session *session, int32_t stream_id,
                               spdylay_status_code status_code,
                               void *user_data) {
   auto client = static_cast<Client *>(user_data);
-  auto req_stat = static_cast<RequestStat *>(
-      spdylay_session_get_stream_user_data(session, stream_id));
-  client->on_stream_close(stream_id, status_code == SPDYLAY_OK, req_stat);
+  client->on_stream_close(stream_id, status_code == SPDYLAY_OK);
 }
 } // namespace
 
@@ -130,8 +126,7 @@ ssize_t file_read_callback(spdylay_session *session, int32_t stream_id,
                            spdylay_data_source *source, void *user_data) {
   auto client = static_cast<Client *>(user_data);
   auto config = client->worker->config;
-  auto req_stat = static_cast<RequestStat *>(
-      spdylay_session_get_stream_user_data(session, stream_id));
+  auto req_stat = client->get_req_stat(stream_id);
 
   ssize_t nread;
   while ((nread = pread(config->data_fd, buf, length, req_stat->data_offset)) ==
@@ -185,7 +180,7 @@ void SpdySession::on_connect() {
   client_->signal_write();
 }
 
-int SpdySession::submit_request(RequestStat *req_stat) {
+int SpdySession::submit_request() {
   int rv;
   auto config = client_->worker->config;
   auto &nv = config->nv[client_->reqidx++];
@@ -197,7 +192,7 @@ int SpdySession::submit_request(RequestStat *req_stat) {
   spdylay_data_provider prd{{0}, file_read_callback};
 
   rv = spdylay_submit_request(session_, 0, nv.data(),
-                              config->data_fd == -1 ? nullptr : &prd, req_stat);
+                              config->data_fd == -1 ? nullptr : &prd, nullptr);
 
   if (rv != 0) {
     return -1;

src/h2load_spdy_session.h

@@ -40,7 +40,7 @@ public:
   SpdySession(Client *client, uint16_t spdy_version);
   virtual ~SpdySession();
   virtual void on_connect();
-  virtual int submit_request(RequestStat *req_stat);
+  virtual int submit_request();
   virtual int on_read(const uint8_t *data, size_t len);
   virtual int on_write();
   virtual void terminate();