No-wait mode

User can now enable no-wait mode, which chooses whether we use the EVRUN_NOWAIT flag in ev_run. The default is off, so that we don't use 100% CPU. Note added in tutorial to enable when performance is critical. Added to the speed test examples. Bump to 0.2.1. Remove patch number from HISTORY entry - that's what the git log is for. Make note on minor release.

No-wait mode
User can now enable no-wait mode, which chooses whether we use the EVRUN_NOWAIT flag in ev_run. The default is off, so that we don't use 100% CPU. Note added in tutorial to enable when performance is critical. Added to the speed test examples. Bump to 0.2.1. Remove patch number from HISTORY entry - that's what the git log is for. Make note on minor release.
Hayk Martirosyan
1 parent 696e1246
Showing 11 changed files with 54 additions and 11 deletions
CMakeLists.txt
HISTORY.md
README.md
examples/lpush_benchmark.cpp
examples/speed_test_async.cpp
examples/speed_test_async_multi.cpp
examples/speed_test_pubsub.cpp
examples/speed_test_sync.cpp
include/redox/client.hpp
include/redox/subscriber.hpp
src/client.cpp
@@ -3,7 +3,7 @@ project(redox)
 set(REDOX_VERSION_MAJOR 0)
 set(REDOX_VERSION_MINOR 2)
-set(REDOX_VERSION_PATCH 0)
+set(REDOX_VERSION_PATCH 1)
 set(REDOX_VERSION_STRING ${REDOX_VERSION_MAJOR}.${REDOX_VERSION_MINOR}.${REDOX_VERSION_PATCH})
 option(lib "Build Redox as a dynamic library." ON)
 # Release History
-## 0.2.0 (2015-01-31)
+## 0.2 (2015-01-31)
 * Move to vector of strings as input, to handle arbitrary data better and
 improve speed.
 * Add doxygen docs.
 * Move all init code out of constructors into .connect methods.
-## 0.1.0 (2015-01-27)
+## 0.1 (2015-01-27)
 First versioned release after many nights of segfaults and memory leaks.
-## 0.0.0 (2014-12-20)
+## 0.0 (2014-12-20)
 Desire to use Redis in C++, but unhappy with existing clients.
@@ -41,8 +41,7 @@ local Redis server.
  * `speed_test_sync` over TCP: **21,072 commands/s**
  * `speed_test_sync` over Unix socket: **24,911 commands/s**
-Results are comparable to that of a mid-range laptop. On a high-end machine, performance
-can be much higher.
+A mid-range laptop gives comparable results. Numbers can be much higher on a high-end machine.
 ## Tutorial
 This section introduces the main features of redox. Look in `examples/` for more inspiration.
@@ -231,6 +230,12 @@ a vector of strings as needed by its API. `rdx.strToVec(&quot;GET foo&quot;)`
 will return an `std::vector<std::string>` containing `GET` and `foo`
 as entries. `rdx.vecToStr({"GET", "foo"})` will return the string `GET foo`.
+#### No-Wait Mode
+Redox provides a no-wait mode, which tells the event loop not to sleep
+in between processing events. It means that the event thread will run
+at 100% CPU, but it can greatly improve performance when critical. It is
+disabled by default and can be enabled with `rdx.noWait(true);`.
+
 ## Reply types
 These the available template parameters in redox and the Redis
 [return types](http://redis.io/topics/protocol) they can hold.
@@ -17,6 +17,7 @@ double time_s() {
 int main(int argc, char* argv[]) {
   redox::Redox rdx;
+
   if(!rdx.connect()) return 1;
   rdx.del("test");
@@ -19,6 +19,8 @@ double time_s() {
 int main(int argc, char* argv[]) {
   Redox rdx;
+  rdx.noWait(true);
+
   if(!rdx.connectUnix("/var/run/redis/redis.sock")) return 1;
   if(rdx.set("simple_loop:count", "0")) {
@@ -20,6 +20,8 @@ double time_s() {
 int main(int argc, char* argv[]) {
   Redox rdx = {cout, redox::log::Debug};
+  rdx.noWait(true);
+
   if(!rdx.connect("localhost", 6379)) return 1;
   if(rdx.set("simple_loop:count", "0")) {
@@ -14,7 +14,10 @@ double time_s() {
 int main(int argc, char *argv[]) {
   Redox rdx_pub;
+  rdx_pub.noWait(true);
+
   Subscriber rdx_sub;
+  rdx_sub.noWait(true);
   if(!rdx_pub.connect()) return 1;
   if(!rdx_sub.connect()) return 1;
@@ -18,6 +18,8 @@ double time_s() {
 int main(int argc, char* argv[]) {
   Redox rdx;
+  rdx.noWait(true);
+
   if(!rdx.connect("localhost", 6379)) return 1;
   if(rdx.commandSync({"SET", "simple_loop:count", "0"})) {
@@ -82,6 +82,18 @@ public:
   ~Redox();
   /**
+  * Enables or disables 'no-wait' mode. If enabled, no-wait mode means that the
+  * event loop does not pause in between processing events. It can greatly increase
+  * the throughput (commands per second),but means that the event thread will run at
+  * 100% CPU. Enable when performance is critical and you can spare a core. Default
+  * is off.
+  *
+  * Implementation note: When enabled, the event thread calls libev's ev_run in a
+  *                      loop with the EVRUN_NOWAIT flag.
+  */
+  void noWait(bool state);
+
+  /**
   * Connects to Redis over TCP and starts an event loop in a separate thread. Returns
   * true once everything is ready, or false on failure.
   */
@@ -340,6 +352,9 @@ private:
   // Dynamically allocated libev event loop
   struct ev_loop* evloop_;
+  // No-wait mode for high-performance
+  std::atomic_bool nowait_ = {false};
+
   // Asynchronous watchers
   ev_async watcher_command_; // For processing commands
   ev_async watcher_stop_; // For breaking the loop
@@ -42,6 +42,11 @@ public:
   ~Subscriber();
   /**
+  * Same as .noWait() on a Redox instance.
+  */
+  void noWait(bool state) { rdx_.noWait(state); }
+
+  /**
   * Same as .connect() on a Redox instance.
   */
   bool connect(
@@ -200,6 +200,12 @@ bool Redox::initHiredis() {
   return true;
 }
+void Redox::noWait(bool state) {
+  if(state) logger_.info() << "No-wait mode enabled.";
+  else logger_.info() << "No-wait mode disabled.";
+  nowait_ = state;
+}
+
 void breakEventLoop(struct ev_loop* loop, ev_async* async, int revents) {
   ev_break(loop, EVBREAK_ALL);
 }
@@ -237,12 +243,14 @@ void Redox::runEventLoop() {
   running_ = true;
   running_waiter_.notify_one();
-  // Run the event loop
-  // TODO this hogs resources, but ev_run(evloop_) without
-  // the manual loop is slower. Maybe use a CV to run sparsely
-  // unless there are commands to process?
+  // Run the event loop, using NOWAIT if enabled for maximum
+  // throughput by avoiding any sleeping
   while (!to_exit_) {
-    ev_run(evloop_, EVRUN_NOWAIT);
+    if(nowait_) {
+      ev_run(evloop_, EVRUN_NOWAIT);
+    } else {
+      ev_run(evloop_);
+    }
   }
   logger_.info() << "Stop signal detected. Closing down event loop.";