Merge pull request apache#1327 from lorinlee/fix-typo

bthread/timer_thread: fix typo

src/bthread/timer_thread.cpp

@@ -244,11 +244,11 @@ TimerThread::TaskId TimerThread::schedule(
 
 // Notice that we don't recycle the Task in this function, let TimerThread::run
 // do it. The side effect is that we may allocated many unscheduled tasks before
-// TimerThread wakes up. The number is approximiately qps * timeout_s. Under the
+// TimerThread wakes up. The number is approximately qps * timeout_s. Under the
 // precondition that ResourcePool<Task> caches 128K for each thread, with some
 // further calculations, we can conclude that in a RPC scenario:
 //   when timeout / latency < 2730 (128K / sizeof(Task))
-// unscheduled tasks do not occupy addititonal memory. 2730 is a large ratio
+// unscheduled tasks do not occupy additional memory. 2730 is a large ratio
 // between timeout and latency in most RPC scenarios, this is why we don't
 // try to reuse tasks right now inside unschedule() with more complicated code.
 int TimerThread::unschedule(TaskId task_id) {