From 91f15d09253e4ae369dafc1c11d4c72c7a93cb0c Mon Sep 17 00:00:00 2001
From: Boris Kolpackov <boris@codesynthesis.com>
Date: Mon, 15 May 2023 09:54:02 +0200
Subject: Redo priority monitor mode detection to obtain priority range

---
 bbot/agent/agent.cxx | 51 +++++++++++++++++++++++++++++++++------------------
 1 file changed, 33 insertions(+), 18 deletions(-)

diff --git a/bbot/agent/agent.cxx b/bbot/agent/agent.cxx
index 1647fcf..edd6422 100644
--- a/bbot/agent/agent.cxx
+++ b/bbot/agent/agent.cxx
@@ -2003,36 +2003,53 @@ try
     toolchain_lock& tl (er.first);
     bootstrapped_machines& ms (er.second);
 
-    // Determine if we should operate in the priority monitor mode and, if so,
-    // the lower bound on the priorities that we should consider.
+    // Determine the existing task priority range (using [0,0] if there are
+    // none) as well as whether we we should operate in the priority monitor
+    // mode.
     //
-    optional<uint64_t> prio_mon;
-    if (inst_max != 0)
+    uint64_t prio_min (0);
+    uint64_t prio_max (0);
+    bool     prio_mon (false);
     {
-      uint16_t           busy (0); // Machines locked by other processes.
-      optional<uint64_t> prio;
+      uint16_t busy (0); // Number of machines locked by other processes.
+      bool task (false); // There is a machine performaing a task.
 
       for (const bootstrapped_machine& m: ms)
       {
         if (!m.lock.locked ())
         {
           ++busy;
-          if (m.lock.prio && (!prio || *m.lock.prio < *prio))
-            prio = *m.lock.prio;
+
+          if (m.lock.prio) // Not bootstrapping/suspended.
+          {
+            task = true;
+
+            if (prio_min > *m.lock.prio)
+              prio_min = *m.lock.prio;
+
+            if (prio_max < *m.lock.prio)
+              prio_max = *m.lock.prio;
+          }
         }
       }
 
-      assert (busy <= inst_max);
-
-      if (busy == inst_max)
+      if (inst_max != 0)
       {
-        if (!prio) // All bootstrapping/suspended.
+        assert (busy <= inst_max);
+
+        if (busy == inst_max)
         {
-          sleep = rand_sleep ();
-          continue;
-        }
+          if (!task) // All bootstrapping/suspended.
+          {
+            sleep = rand_sleep ();
+            continue;
+          }
+
+          l1 ([&]{trace << "priority monitor, range [" << prio_min << ", "
+                        << prio_max << "]";});
 
-        prio_mon = *prio;
+          prio_mon = true;
+        }
       }
     }
 
@@ -2040,8 +2057,6 @@ try
     //
     if (prio_mon)
     {
-      l1 ([&]{trace << "priority monitor, lower bound " << *prio_mon;});
-
       sleep = rand_sleep () / 2;
       continue;
     }
-- 
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