replace ad hoc driver loading with a proper driver manager, new DDK, new PnP manager with device matching, asynchronous startup, resource ownership and removal, add shared PCI capability helpers, replace typed, rigid services with a proper service manager, implement proper system shutdown and restart, shutting down unloads drivers and shuts down services, add simple power button, remove heavyweight boot self-tests and SMP stress runs, add monotonic timestamps to kernel debug output, fruitless USB and PS/2 fixes, make test builds opt in.

code/kernel/mm_phys.c

@@ -794,12 +794,14 @@ void MmPfnQueryStats(MM_PFN_STATS* out) {
     MM_PFN_STATS stats;
     memset(&stats, 0, sizeof(stats));
 
-    uintptr_t flags = KeAcquireSpinlock(&gPfnLock);
-    stats.TotalFrames = (uint64_t)gTotalFrames;
-    stats.FreeFrames = (uint64_t)gFreeFrames;
-    stats.UsedFrames = stats.TotalFrames - stats.FreeFrames;
-
-    for (size_t pfn = 0; pfn < gMaxPfn; pfn++) {
+    // Detailed statistics are diagnostic snapshots. Scan bounded PFN batches
+    // so an ordinary query cannot monopolize the global allocator lock on
+    // machines with millions of physical frames. Counters are sampled at end.
+    const size_t pfnCount = gMaxPfn;
+    for (size_t base = 0; base < pfnCount;) {
+        size_t end = pfnCount - base < 1024u ? pfnCount : base + 1024u;
+        uintptr_t flags = KeAcquireSpinlock(&gPfnLock);
+        for (size_t pfn = base; pfn < end; ++pfn) {
         const MM_PFN* entry = &gPfnDatabase[pfn];
         if (entry->State == MmPfnStateInvalid)
             continue;
@@ -847,8 +849,15 @@ void MmPfnQueryStats(MM_PFN_STATS* out) {
         case MmPfnUseMmio:           stats.MmioFrames++; break;
         default: break;
         }
+        }
+        KeReleaseSpinlock(&gPfnLock, flags);
+        base = end;
     }
 
+    uintptr_t flags = KeAcquireSpinlock(&gPfnLock);
+    stats.TotalFrames = (uint64_t)gTotalFrames;
+    stats.FreeFrames = (uint64_t)gFreeFrames;
+    stats.UsedFrames = stats.TotalFrames - stats.FreeFrames;
     stats.AvailableFrames = stats.FreeFrames + stats.ReclaimableFrames;
 
     stats.AllocationCount = gPfnAllocations;