This appears to improve cpu usage since launching a new thread is more expensive than performing a small amount of inline logic.
However, needs testing at scale.
When Melanie added the web fetch inventory throttle to core, she made the long poll requests (EQs) effectively be handled on an active loop. All those requests, if they existed, were being constantly dequeued, checked for events (which most often they didn't have), and requeued again. This was an active loop thread on a 100ms cycle!
This fixes the issue. Now the inventory requests, if they aren't ready to be served, are placed directly back in the queue, but the long poll requests aren't placed there until there are events ready to be sent or timeout has been reached.
This puts the LongPollServiceWatcherThread back to 1sec cycle, as it was before.
This reverts commit 21a09ad3ad.
After more analysis and discussion, it is apparant that the Count(), Contains() and GetQueueArray() cannot be made thread-safe anyway without external locking
And this change appears to have a positive impact on performance.
I still believe that Monitor.Exit() will not release any thread for Monitor.Wait(), as per http://msdn.microsoft.com/en-gb/library/vstudio/system.threading.monitor.exit%28v=vs.100%29.aspx
so this should in theory make no difference, though mono implementation issues could possibly be coming into play.
This reverts commit 42e2a0d66e
Reverting because unfortunately this introduces race conditions because Contains(), Count() and GetQueueArray() may now end up returning the wrong result if another thread performs a simultaneous update on m_queue.
Code such as PollServiceRequestManager.Stop() relies on the count being correct otherwise a request may be lost.
Also, though some of the internal queue methods do not affect state, they are not thread-safe and could return the wrong result generating the same problem
lock() generates Monitor.Enter() and Monitor.Exit() under the covers. Monitor.Exit() does not cause Monitor.Wait() to exist, only Pulse() and PulseAll() will do this
Reverted with agreement.
This adds explicit cap poll handler supporting to the Caps classes rather than relying on callers to do the complicated coding.
Other refactoring was required to get logic into the right places to support this.
17:14:28 - [APPLICATION]:
APPLICATION EXCEPTION DETECTED: System.UnhandledExceptionEventArgs
Exception: System.InvalidOperationException: Operation is not valid due to the current state of the object
at System.Collections.Generic.Queue`1[OpenSim.Region.ClientStack.Linden.WebFetchInvDescModule+aPollRequest].Peek () [0x00011] in /root/install/mono-3.1.0/mono/mcs/class/System/System.Collections.Generic/Queue.cs:158
at System.Collections.Generic.Queue`1[OpenSim.Region.ClientStack.Linden.WebFetchInvDescModule+aPollRequest].Dequeue () [0x00000] in /root/install/mono-3.1.0/mono/mcs/class/System/System.Collections.Generic/Queue.cs:140
at OpenSim.Framework.DoubleQueue`1[OpenSim.Region.ClientStack.Linden.WebFetchInvDescModule+aPollRequest].Dequeue (TimeSpan wait, OpenSim.Region.ClientStack.Linden.aPollRequest& res) [0x0004e] in /home/avacon/opensim_2013-07-14/OpenSim/Framework/Util.cs:2297
Justin Clark-Casey (justincc)