Make llcoro::scheduler log coros that run too long between yields.

Introduce LLCoros::CoroData::mHistogram, a map of cutoff times (bucket
breakpoints) with counts of occurrences. The idea is that mHistogram counts
how many times the real time taken by a particular coroutine resumption falls
into one of those buckets. Initialize the map with guessed buckets; these are
set in llcoros.cpp so they can be changed without requiring extensive rebuilds.

scheduler::pick_next() now records the timestamp and fiber context just before
the fiber manager resumes the next coroutine. If the next pick_next() call
reveals that the previous resumption took longer than the minimum bucket
breakpoint, it increments the appropriate bucket counter and logs the instance.

LLCoros::toplevel() reports nonzero mHistogram entries on coroutine
termination.

1 files changed, 9 insertions, 6 deletions

diff --git a/indra/llcommon/coro_scheduler.h b/indra/llcommon/coro_scheduler.h
index eee2d746b5..7af90685dc 100644
--- a/indra/llcommon/coro_scheduler.h
+++ b/indra/llcommon/coro_scheduler.h
@@ -47,17 +47,20 @@ public:
     static void use();
 
 private:
-    // This is the fiber::id of the main fiber. We use this to discover
-    // whether the fiber passed to awakened() is in fact the main fiber.
+    LL::WorkQueue::ptr_t getWorkQueue();
+
+    // This is the fiber::id of the main fiber.
     boost::fibers::fiber::id mMainID;
-    // This context* is nullptr until awakened() notices that the main fiber
-    // has become ready, at which point it contains the main fiber's context*.
+    // This context* is nullptr while the main fiber is running or suspended,
+    // but is set to the main fiber's context each time the main fiber is ready.
     boost::fibers::context* mMainCtx{};
-    // Set when pick_next() returns the main fiber.
-    bool mMainRunning{ false };
+    // Remember the context returned by the previous pick_next() call.
+    boost::fibers::context* mPrevCtx{};
     // If it's been at least this long since the last time the main fiber got
     // control, jump it to the head of the queue.
     F64 mTimeslice{ DEFAULT_TIMESLICE };
+    // Time when we resumed the most recently running fiber
+    F64 mResumeTime{ 0 };
     // Timestamp as of the last time we suspended the main fiber.
     F64 mMainLast{ 0 };
     // Timestamp of start time