Scheduler: Implement timer source switching API

Scheduler: Switch default timer source to lores / epoll()

Scheduler/Scheduler.cci

@@ -54,6 +54,23 @@ prefix_ unsigned senf::scheduler::hangCount()
     return scheduler::detail::FIFORunner::instance().hangCount();
 }
 
+prefix_ void senf::scheduler::hiresTimers()
+{
+    detail::TimerDispatcher::instance().setTimerSource(
+        std::auto_ptr<TimerSource>(new POSIXTimerSource()));
+}
+
+prefix_ void senf::scheduler::loresTimers()
+{
+    detail::TimerDispatcher::instance().setTimerSource(
+        std::auto_ptr<TimerSource>(new PollTimerSource()));
+}
+
+prefix_ bool senf::scheduler::haveScalableHiresTimers()
+{
+    return false;
+}
+
 ///////////////////////////////cci.e///////////////////////////////////////
 #undef prefix_
 

Scheduler/Scheduler.hh

@@ -232,6 +232,32 @@ namespace scheduler {
     /** \brief Number of watchdog events */
     unsigned hangCount(); 
 
+    /** \brief Switch to using hi resolution timers
+        
+        By default, timers are implemented directly using epoll. This however restricts the timer
+        resolution to that of the kernel HZ value.
+
+        High resolution timers are implemented either using POSIX timers or, when available, using
+        the Linux special \c timerfd() syscall.
+
+        POSIX timers are delivered using signals. A high timer load this increases the signal load
+        considerably. \c timerfd()'s are delivered on a file descriptor and thus don't have such a
+        scalability issue.
+
+        \warning The timer source must not be switched from a scheduler callback
+     */
+    void hiresTimers();
+
+    /** \brief Switch back to using epoll for timing
+        \see hiresTimers()
+     */
+    void loresTimers();
+
+    /** \brief return \c true, if \c timerfd() timing is available, \c false otherwise
+        \see hiresTimers()
+     */
+    bool haveScalableHiresTimers();
+
     /** \brief Restart scheduler
         
         This call will restart all scheduler dispatchers (timers, signals, file descriptors). This

Scheduler/TimerEvent.cc

@@ -34,7 +34,7 @@
 ///////////////////////////////cc.p////////////////////////////////////////
 
 prefix_ senf::scheduler::detail::TimerDispatcher::TimerDispatcher()
-    : source_ (new POSIXTimerSource())
+    : source_ (new PollTimerSource())
 {}
 
 prefix_ senf::scheduler::detail::TimerDispatcher::~TimerDispatcher()

Scheduler/TimerEvent.cci

@@ -98,6 +98,12 @@ prefix_ bool senf::scheduler::detail::TimerDispatcher::empty()
     return timers_.empty();
 }
 
+prefix_ void senf::scheduler::detail::TimerDispatcher::
+setTimerSource(std::auto_ptr<TimerSource> timerSource)
+{
+    source_.reset(timerSource.release());
+}
+
 ///////////////////////////////cci.e///////////////////////////////////////
 #undef prefix_
 

Scheduler/TimerEvent.ih

@@ -65,6 +65,8 @@ namespace detail {
 
         bool empty() const;
 
+        void setTimerSource(std::auto_ptr<TimerSource> timerSource);
+
     protected:
 
     private: