nghttpx: Reduce epoll_ctl call

src/shrpx_client_handler.cc

@@ -256,7 +256,7 @@ ClientHandler::ClientHandler(bufferevent *bev,
     CLOG(FATAL, this) << "bufferevent_add_to_rate_limit_group() failed";
   }
 
-  bufferevent_enable(bev_, EV_READ | EV_WRITE);
+  util::bev_enable_unless(bev_, EV_READ | EV_WRITE);
   bufferevent_setwatermark(bev_, EV_READ, 0, SHRPX_READ_WATERMARK);
   set_upstream_timeouts(&get_config()->upstream_read_timeout,
                         &get_config()->upstream_write_timeout);
@@ -298,7 +298,7 @@ ClientHandler::~ClientHandler()
 
   bufferevent_remove_from_rate_limit_group(bev_);
 
-  bufferevent_disable(bev_, EV_READ | EV_WRITE);
+  util::bev_disable_unless(bev_, EV_READ | EV_WRITE);
   bufferevent_free(bev_);
 
   if(ssl_) {

src/shrpx_http2_session.cc

@@ -89,7 +89,7 @@ int Http2Session::disconnect()
   }
   if(bev_) {
     int fd = bufferevent_getfd(bev_);
-    bufferevent_disable(bev_, EV_READ | EV_WRITE);
+    util::bev_disable_unless(bev_, EV_READ | EV_WRITE);
     bufferevent_free(bev_);
     bev_ = nullptr;
     if(fd != -1) {
@@ -219,7 +219,7 @@ int Http2Session::init_notification()
     close(sockpair[1]);
     return -1;
   }
-  bufferevent_enable(rdbev_, EV_READ);
+  util::bev_enable_unless(rdbev_, EV_READ);
   bufferevent_setcb(rdbev_, notify_readcb, nullptr, notify_eventcb, this);
   return 0;
 }
@@ -417,7 +417,7 @@ int Http2Session::initiate_connection()
       close(fd);
       return SHRPX_ERR_NETWORK;
     }
-    bufferevent_enable(bev_, EV_READ);
+    util::bev_enable_unless(bev_, EV_READ);
     bufferevent_set_timeouts(bev_, &get_config()->downstream_read_timeout,
                              &get_config()->downstream_write_timeout);
 
@@ -534,7 +534,7 @@ int Http2Session::initiate_connection()
     }
 
     bufferevent_setwatermark(bev_, EV_READ, 0, SHRPX_READ_WATERMARK);
-    bufferevent_enable(bev_, EV_READ);
+    util::bev_enable_unless(bev_, EV_READ);
     bufferevent_setcb(bev_, readcb, writecb, eventcb, this);
     // Set timeout for HTTP2 session
     reset_timeouts();

src/shrpx_http_downstream_connection.cc

@@ -54,7 +54,7 @@ HttpDownstreamConnection::HttpDownstreamConnection
 HttpDownstreamConnection::~HttpDownstreamConnection()
 {
   if(bev_) {
-    bufferevent_disable(bev_, EV_READ | EV_WRITE);
+    util::bev_disable_unless(bev_, EV_READ | EV_WRITE);
     bufferevent_free(bev_);
   }
   // Downstream and DownstreamConnection may be deleted
@@ -127,7 +127,7 @@ int HttpDownstreamConnection::attach_downstream(Downstream *downstream)
   response_htp_.data = downstream_;
 
   bufferevent_setwatermark(bev_, EV_READ, 0, SHRPX_READ_WATERMARK);
-  bufferevent_enable(bev_, EV_READ);
+  util::bev_enable_unless(bev_, EV_READ);
   bufferevent_setcb(bev_,
                     upstream->get_downstream_readcb(),
                     upstream->get_downstream_writecb(),
@@ -369,7 +369,7 @@ void HttpDownstreamConnection::detach_downstream(Downstream *downstream)
   }
   downstream_ = nullptr;
   ioctrl_.force_resume_read();
-  bufferevent_enable(bev_, EV_READ);
+  util::bev_enable_unless(bev_, EV_READ);
   bufferevent_setcb(bev_, 0, 0, idle_eventcb, this);
   // On idle state, just enable read timeout. Normally idle downstream
   // connection will get EOF from the downstream server and closed.

src/shrpx_io_control.cc

@@ -26,6 +26,10 @@
 
 #include <algorithm>
 
+#include "util.h"
+
+using namespace nghttp2;
+
 namespace shrpx {
 
 IOControl::IOControl(bufferevent *bev)
@@ -45,7 +49,7 @@ void IOControl::pause_read(IOCtrlReason reason)
 {
   rdbits_ |= reason;
   if(bev_) {
-    bufferevent_disable(bev_, EV_READ);
+    util::bev_disable_unless(bev_, EV_READ);
   }
 }
 
@@ -54,7 +58,7 @@ bool IOControl::resume_read(IOCtrlReason reason)
   rdbits_ &= ~reason;
   if(rdbits_ == 0) {
     if(bev_) {
-      bufferevent_enable(bev_, EV_READ);
+      util::bev_enable_unless(bev_, EV_READ);
     }
     return true;
   } else {
@@ -66,7 +70,7 @@ void IOControl::force_resume_read()
 {
   rdbits_ = 0;
   if(bev_) {
-    bufferevent_enable(bev_, EV_READ);
+    util::bev_enable_unless(bev_, EV_READ);
   }
 }
 

src/shrpx_listen_handler.cc

@@ -112,7 +112,7 @@ void worker_writecb(bufferevent *bev, void *ptr)
 
   // Disable bev so that this won' be called accidentally in the
   // future.
-  bufferevent_disable(bev, EV_READ | EV_WRITE);
+  util::bev_disable_unless(bev, EV_READ | EV_WRITE);
 }
 } // namespace
 #endif // NOTHREADS

src/shrpx_worker.cc

@@ -113,7 +113,7 @@ void Worker::run()
      http2session.get(),
      http1_connect_blocker.get());
 
-  bufferevent_enable(bev.get(), EV_READ);
+  util::bev_enable_unless(bev.get(), EV_READ);
   bufferevent_setcb(bev.get(), readcb, nullptr, eventcb, receiver.get());
 
   event_base_loop(evbase.get(), 0);

src/util.cc

@@ -657,6 +657,24 @@ char* get_exec_path(int argc, char **const argv, const char *cwd)
   return path;
 }
 
+void bev_enable_unless(bufferevent *bev, int events)
+{
+  if((bufferevent_get_enabled(bev) & events) == events) {
+    return;
+  }
+
+  bufferevent_enable(bev, events);
+}
+
+void bev_disable_unless(bufferevent *bev, int events)
+{
+  if((bufferevent_get_enabled(bev) & events) == 0) {
+    return;
+  }
+
+  bufferevent_disable(bev, events);
+}
+
 } // namespace util
 
 } // namespace nghttp2

src/util.h

@@ -38,6 +38,7 @@
 #include <memory>
 
 #include <event2/buffer.h>
+#include <event2/bufferevent.h>
 
 #include "http-parser/http_parser.h"
 
@@ -481,6 +482,12 @@ std::string ascii_dump(const uint8_t *data, size_t len);
 // it.
 char* get_exec_path(int argc, char **const argv, const char *cwd);
 
+// These functions are provided to reduce epoll_ctl syscall.  Avoid
+// calling bufferevent_enable/disable() unless it is required by
+// sniffing current enabled events.
+void bev_enable_unless(bufferevent *bev, int events);
+void bev_disable_unless(bufferevent *bev, int events);
+
 } // namespace util
 
 } // namespace nghttp2