Use freemem when Proxmox VM status memory disagrees (#1319)

internal/monitoring/vm_memory_selection.go

@@ -6,7 +6,8 @@ import (
 	"github.com/rcourtman/pulse-go-rewrite/pkg/proxmox"
 )
 
-const vmMemInfoGapTolerance uint64 = 16 * 1024 * 1024 // 16 MiB
+const vmMemInfoGapTolerance uint64 = 16 * 1024 * 1024            // 16 MiB
+const vmStatusMemoryMismatchTolerance uint64 = 128 * 1024 * 1024 // 128 MiB
 
 type vmMemAvailableSelection struct {
 	Available      uint64
@@ -102,8 +103,14 @@ func selectVMLowTrustUsedMemory(memTotal uint64, status *proxmox.VMStatus) vmLow
 	}
 
 	if status.Mem > 0 {
-		if status.Mem >= memTotal && hasFreeFallback && freeDerivedUsed < memTotal {
-			return vmLowTrustUsedSelection{Used: freeDerivedUsed, Source: "status-freemem"}
+		if hasFreeFallback && freeDerivedUsed < status.Mem {
+			statusMemPlusFree := saturatingAddUint64(status.Mem, status.FreeMem)
+			if status.Mem >= memTotal && freeDerivedUsed < memTotal {
+				return vmLowTrustUsedSelection{Used: freeDerivedUsed, Source: "status-freemem"}
+			}
+			if statusMemPlusFree > memTotal+vmStatusMemoryMismatchTolerance {
+				return vmLowTrustUsedSelection{Used: freeDerivedUsed, Source: "status-freemem"}
+			}
 		}
 		return vmLowTrustUsedSelection{Used: status.Mem, Source: "status-mem"}
 	}

internal/monitoring/vm_memory_selection_test.go

@@ -132,6 +132,16 @@ func TestSelectVMLowTrustUsedMemory(t *testing.T) {
 			wantUsed:   3 * giB,
 			wantSource: "status-freemem",
 		},
+		{
+			name:     "falls back to status freemem when status mem and freemem are materially inconsistent",
+			memTotal: 8 * giB,
+			status: &proxmox.VMStatus{
+				Mem:     7920 * 1024 * 1024,
+				FreeMem: 5 * giB,
+			},
+			wantUsed:   3 * giB,
+			wantSource: "status-freemem",
+		},
 		{
 			name:     "uses status freemem when status mem is absent",
 			memTotal: 8 * giB,
@@ -148,6 +158,16 @@ func TestSelectVMLowTrustUsedMemory(t *testing.T) {
 			wantUsed:   0,
 			wantSource: "",
 		},
+		{
+			name:     "keeps status mem when freemem only shows tiny headroom",
+			memTotal: 8 * giB,
+			status: &proxmox.VMStatus{
+				Mem:     8*giB - (64 * 1024 * 1024),
+				FreeMem: 64 * 1024 * 1024,
+			},
+			wantUsed:   8*giB - (64 * 1024 * 1024),
+			wantSource: "status-mem",
+		},
 	}
 
 	for _, tt := range tests {