SL-18809: Add WorkSchedule; remove timestamps from WorkQueue.

For work queues that don't need timestamped tasks, eliminate the overhead of a
priority queue ordered by timestamp. Timestamped task support moves to
WorkSchedule. WorkQueue is a simpler queue that just waits for work.

Both WorkQueue and WorkSchedule can be accessed via new WorkQueueBase API. Of
course the WorkQueueBase API doesn't deal with timestamps, but a WorkSchedule
can be accessed directly to post timestamped tasks and then handled normally
(e.g. by ThreadPool) to run them.

Most ThreadPool functionality migrates to new ThreadPoolBase class, with
template subclass ThreadPoolUsing<WorkQueue> or ThreadPoolUsing<WorkSchedule>
depending on need. ThreadPool is now an alias for ThreadPoolUsing<WorkQueue>.
Importantly, ThreadPoolUsing::getQueue() delivers a reference to the specific
queue subclass type, so you can post timestamped tasks on a queue retrieved
from ThreadPoolUsing<WorkSchedule>::getQueue().

Since ThreadPool is no longer a simple class but an alias for a particular
template specialization, introduce threadpool_fwd.h to forward-declare it.

Recast workqueue_test.cpp to exercise WorkSchedule, since some of the tests
are time-based. A future todo would be to exercise each applicable test with
both WorkQueue and WorkSchedule.

1 files changed, 13 insertions, 13 deletions

diff --git a/indra/llcommon/tests/workqueue_test.cpp b/indra/llcommon/tests/workqueue_test.cpp
index 1d73f7aa0d..41aa858084 100644
--- a/indra/llcommon/tests/workqueue_test.cpp
+++ b/indra/llcommon/tests/workqueue_test.cpp
@@ -38,7 +38,7 @@ namespace tut
 {
     struct workqueue_data
     {
-        WorkQueue queue{"queue"};
+        WorkSchedule queue{"queue"};
     };
     typedef test_group<workqueue_data> workqueue_group;
     typedef workqueue_group::object object;
@@ -49,8 +49,8 @@ namespace tut
     {
         set_test_name("name");
         ensure_equals("didn't capture name", queue.getKey(), "queue");
-        ensure("not findable", WorkQueue::getInstance("queue") == queue.getWeak().lock());
-        WorkQueue q2;
+        ensure("not findable", WorkSchedule::getInstance("queue") == queue.getWeak().lock());
+        WorkSchedule q2;
         ensure("has no name", LLStringUtil::startsWith(q2.getKey(), "WorkQueue"));
     }
 
@@ -73,16 +73,16 @@ namespace tut
     {
         set_test_name("postEvery");
         // record of runs
-        using Shared = std::deque<WorkQueue::TimePoint>;
+        using Shared = std::deque<WorkSchedule::TimePoint>;
         // This is an example of how to share data between the originator of
-        // postEvery(work) and the work item itself, since usually a WorkQueue
+        // postEvery(work) and the work item itself, since usually a WorkSchedule
         // is used to dispatch work to a different thread. Neither of them
         // should call any of LLCond's wait methods: you don't want to stall
         // either the worker thread or the originating thread (conventionally
         // main). Use LLCond or a subclass even if all you want to do is
         // signal the work item that it can quit; consider LLOneShotCond.
         LLCond<Shared> data;
-        auto start = WorkQueue::TimePoint::clock::now();
+        auto start = WorkSchedule::TimePoint::clock::now();
         auto interval = 100ms;
         queue.postEvery(
             interval,
@@ -93,7 +93,7 @@ namespace tut
                 data.update_one(
                     [](Shared& data)
                     {
-                        data.push_back(WorkQueue::TimePoint::clock::now());
+                        data.push_back(WorkSchedule::TimePoint::clock::now());
                     });
                 // by the 3rd call, return false to stop
                 return (++count < 3);
@@ -102,7 +102,7 @@ namespace tut
         // postEvery() running, so run until we have exhausted the iterations
         // or we time out waiting
         for (auto finish = start + 10*interval;
-             WorkQueue::TimePoint::clock::now() < finish &&
+             WorkSchedule::TimePoint::clock::now() < finish &&
              data.get([](const Shared& data){ return data.size(); }) < 3; )
         {
             queue.runPending();
@@ -139,8 +139,8 @@ namespace tut
     void object::test<4>()
     {
         set_test_name("postTo");
-        WorkQueue main("main");
-        auto qptr = WorkQueue::getInstance("queue");
+        WorkSchedule main("main");
+        auto qptr = WorkSchedule::getInstance("queue");
         int result = 0;
         main.postTo(
             qptr,
@@ -171,8 +171,8 @@ namespace tut
     void object::test<5>()
     {
         set_test_name("postTo with void return");
-        WorkQueue main("main");
-        auto qptr = WorkQueue::getInstance("queue");
+        WorkSchedule main("main");
+        auto qptr = WorkSchedule::getInstance("queue");
         std::string observe;
         main.postTo(
             qptr,
@@ -194,7 +194,7 @@ namespace tut
         std::string stored;
         // Try to call waitForResult() on this thread's main coroutine. It
         // should throw because the main coroutine must service the queue.
-        auto what{ catch_what<WorkQueue::Error>(
+        auto what{ catch_what<WorkSchedule::Error>(
                 [this, &stored](){ stored = queue.waitForResult(
                         [](){ return "should throw"; }); }) };
         ensure("lambda should not have run", stored.empty());