From eda264c2821a86505b4ec2a898ff3169ab82f895 Mon Sep 17 00:00:00 2001
From: Nat Goodspeed <nat@lindenlab.com>
Date: Wed, 20 Oct 2021 18:38:36 -0400
Subject: SL-16220: Add a WorkQueue to be serviced by mainloop.

Make LLAppViewer::idle() call LL::WorkQueue::runFor() to dequeue and run some
or all of the pending responses from worker threads.

Add a MainWorkTime setting to specify the time slice the main loop may devote
each frame to servicing such responses.
---
 indra/newview/app_settings/settings.xml | 11 +++++++++++
 indra/newview/llappviewer.cpp           | 18 ++++++++++++++++++
 2 files changed, 29 insertions(+)

(limited to 'indra/newview')

diff --git a/indra/newview/app_settings/settings.xml b/indra/newview/app_settings/settings.xml
index 05c3fc3bfe..802453d508 100644
--- a/indra/newview/app_settings/settings.xml
+++ b/indra/newview/app_settings/settings.xml
@@ -3858,6 +3858,17 @@
         <key>Value</key>
         <integer>1</integer>
     </map>
+    <key>MainWorkTime</key>
+    <map>
+        <key>Comment</key>
+        <string>Max time per frame devoted to mainloop work queue (in milliseconds)</string>
+        <key>Persist</key>
+        <integer>1</integer>
+        <key>Type</key>
+        <string>F32</string>
+        <key>Value</key>
+        <real>0.1</real>
+    </map>
     <key>QueueInventoryFetchTimeout</key>
     <map>
         <key>Comment</key>
diff --git a/indra/newview/llappviewer.cpp b/indra/newview/llappviewer.cpp
index 722a6caa65..7c932a3959 100644
--- a/indra/newview/llappviewer.cpp
+++ b/indra/newview/llappviewer.cpp
@@ -233,6 +233,8 @@
 #include "llavatariconctrl.h"
 #include "llgroupiconctrl.h"
 #include "llviewerassetstats.h"
+#include "workqueue.h"
+using namespace LL;
 
 // Include for security api initialization
 #include "llsecapi.h"
@@ -366,6 +368,8 @@ BOOL gLogoutInProgress = FALSE;
 
 BOOL gSimulateMemLeak = FALSE;
 
+WorkQueue gMainloopWork("mainloop");
+
 ////////////////////////////////////////////////////////////
 // Internal globals... that should be removed.
 static std::string gArgs;
@@ -5210,6 +5214,20 @@ void LLAppViewer::idle()
 	// Execute deferred tasks.
 	LLDeferredTaskList::instance().run();
 
+	// Service the WorkQueue we use for replies from worker threads.
+	// Use function statics for the timeslice setting so we only have to fetch
+	// and convert MainWorkTime once.
+	static F32 MainWorkTimeRaw = gSavedSettings.getF32("MainWorkTime");
+	static F32Milliseconds MainWorkTimeMs(MainWorkTimeRaw);
+	// MainWorkTime is specified in fractional milliseconds, but std::chrono
+	// uses integer representations. What if we want less than a microsecond?
+	// Use nanoseconds. We're very sure we will never need to specify a
+	// MainWorkTime that would be larger than we could express in
+	// std::chrono::nanoseconds.
+	static std::chrono::nanoseconds MainWorkTimeNanoSec{
+		std::chrono::nanoseconds::rep(MainWorkTimeMs.value() * 1000000)};
+	gMainloopWork.runFor(MainWorkTimeNanoSec);
+
 	// Handle shutdown process, for example,
 	// wait for floaters to close, send quit message,
 	// forcibly quit if it has taken too long
-- 
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