h2load: Print "space savings" to measure header compression efficiency

doc/h2load.h2r

@@ -34,9 +34,13 @@ traffic
     bytes.
   headers
     The  number  of response  header  bytes  from the  server  without
-    decompression.  For HTTP/2, this is the sum of the payload of
-    HEADERS frame.  For SPDY, this is the sum of the payload of
-    SYN_REPLY frame.
+    decompression.  The  ``space savings`` shows efficiency  of header
+    compression.  Let ``decompressed(headers)`` to the number of bytes
+    used for header fields after decompression.  The ``space savings``
+    is calculated  by (1 - ``headers``  / ``decompressed(headers)``) *
+    100.  For HTTP/1.1, this is usually  0.00%, since it does not have
+    header compression.  For HTTP/2 and SPDY, it shows some insightful
+    numbers.
   data
     The number of response body bytes received from the server.
 

src/h2load.cc

@@ -95,8 +95,8 @@ RequestStat::RequestStat() : data_offset(0), completed(false) {}
 Stats::Stats(size_t req_todo)
     : 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_body(0), status(),
-      req_stats(req_todo) {}
+      bytes_total(0), bytes_head(0), bytes_head_decomp(0), bytes_body(0),
+      status(), req_stats(req_todo) {}
 
 Stream::Stream() : status_success(-1) {}
 
@@ -2073,6 +2073,7 @@ int main(int argc, char **argv) {
     stats.req_error += s.req_error;
     stats.bytes_total += s.bytes_total;
     stats.bytes_head += s.bytes_head;
+    stats.bytes_head_decomp += s.bytes_head_decomp;
     stats.bytes_body += s.bytes_body;
 
     for (size_t i = 0; i < stats.status.size(); ++i) {
@@ -2102,7 +2103,13 @@ int main(int argc, char **argv) {
     bps = stats.bytes_total / secd.count();
   }
 
-  std::cout << R"(
+  double header_space_savings = 0.;
+  if (stats.bytes_head_decomp > 0) {
+    header_space_savings =
+        1. - static_cast<double>(stats.bytes_head) / stats.bytes_head_decomp;
+  }
+
+  std::cout << std::fixed << std::setprecision(2) << R"(
 finished in )" << util::format_duration(duration) << ", " << rps << " req/s, "
             << util::utos_with_funit(bps) << R"(B/s
 requests: )" << stats.req_todo << " total, " << stats.req_started
@@ -2113,7 +2120,8 @@ requests: )" << stats.req_todo << " total, " << stats.req_started
 status codes: )" << stats.status[2] << " 2xx, " << stats.status[3] << " 3xx, "
             << stats.status[4] << " 4xx, " << stats.status[5] << R"( 5xx
 traffic: )" << stats.bytes_total << " bytes total, " << stats.bytes_head
-            << " bytes headers, " << stats.bytes_body << R"( bytes data
+            << " bytes headers (space savings " << header_space_savings * 100
+            << "%), " << stats.bytes_body << R"( bytes data
                      min         max         mean         sd        +/- sd
 time for request: )" << std::setw(10) << util::format_duration(ts.request.min)
             << "  " << std::setw(10) << util::format_duration(ts.request.max)

src/h2load.h

@@ -166,8 +166,12 @@ struct Stats {
   // The number of bytes received on the "wire". If SSL/TLS is used,
   // this is the number of decrypted bytes the application received.
   int64_t bytes_total;
-  // The number of bytes received in HEADERS frame payload.
+  // The number of bytes received for header fields.  This is
+  // compressed version.
   int64_t bytes_head;
+  // The number of bytes received for header fields after they are
+  // decompressed.
+  int64_t bytes_head_decomp;
   // The number of bytes received in DATA frame.
   int64_t bytes_body;
   // The number of each HTTP status category, status[i] is status code

src/h2load_http1_session.cc

@@ -99,6 +99,7 @@ int htp_hdr_keycb(http_parser *htp, const char *data, size_t len) {
   auto client = session->get_client();
 
   client->worker->stats.bytes_head += len;
+  client->worker->stats.bytes_head_decomp += len;
   return 0;
 }
 } // namespace
@@ -109,6 +110,7 @@ int htp_hdr_valcb(http_parser *htp, const char *data, size_t len) {
   auto client = session->get_client();
 
   client->worker->stats.bytes_head += len;
+  client->worker->stats.bytes_head_decomp += len;
   return 0;
 }
 } // namespace

src/h2load_http2_session.cc

@@ -51,6 +51,7 @@ int on_header_callback(nghttp2_session *session, const nghttp2_frame *frame,
     return 0;
   }
   client->on_header(frame->hd.stream_id, name, namelen, value, valuelen);
+  client->worker->stats.bytes_head_decomp += namelen + valuelen;
   return 0;
 }
 } // namespace
@@ -63,7 +64,9 @@ int on_frame_recv_callback(nghttp2_session *session, const nghttp2_frame *frame,
       frame->headers.cat != NGHTTP2_HCAT_RESPONSE) {
     return 0;
   }
-  client->worker->stats.bytes_head += frame->hd.length;
+  client->worker->stats.bytes_head +=
+      frame->hd.length - frame->headers.padlen -
+      ((frame->hd.flags & NGHTTP2_FLAG_PRIORITY) ? 5 : 0);
   if (frame->hd.flags & NGHTTP2_FLAG_END_STREAM) {
     client->record_ttfb();
   }

src/h2load_spdy_session.cc

@@ -65,11 +65,18 @@ void on_ctrl_recv_callback(spdylay_session *session, spdylay_frame_type type,
   for (auto p = frame->syn_reply.nv; *p; p += 2) {
     auto name = *p;
     auto value = *(p + 1);
+    auto namelen = strlen(name);
+    auto valuelen = strlen(value);
     client->on_header(frame->syn_reply.stream_id,
-                      reinterpret_cast<const uint8_t *>(name), strlen(name),
-                      reinterpret_cast<const uint8_t *>(value), strlen(value));
+                      reinterpret_cast<const uint8_t *>(name), namelen,
+                      reinterpret_cast<const uint8_t *>(value), valuelen);
+    client->worker->stats.bytes_head_decomp += namelen + valuelen;
   }
-  client->worker->stats.bytes_head += frame->syn_reply.hd.length;
+
+  // Strictly speaking, we have to subtract 2 (unused field) if SPDY
+  // version is 2.  But it is already deprecated, and we don't do
+  // extra work for it.
+  client->worker->stats.bytes_head += frame->syn_reply.hd.length - 4;
 
   if (frame->syn_stream.hd.flags & SPDYLAY_CTRL_FLAG_FIN) {
     client->record_ttfb();