Top: a hyper-thread wears its core's temperature, and the columns line up

The process table carries each logical CPU's core id from sysfs topology; a row with
no reading still has the temperature cells, so the % column is one column.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/metrics/metrics.go

@@ -1011,6 +1011,34 @@ func uidName(uid string) string {
 	return n
 }
 
+// coreIDs maps logical CPUs to physical cores from sysfs topology: on a chip with
+// hyper-threading, CPUs 8–15 are the second threads of cores 0–7, and coretemp names its
+// sensors by core. Read once; the topology does not change while we run.
+var (
+	coreIDsOnce sync.Once
+	coreIDsVal  []int
+)
+
+func coreIDs(n int) []int {
+	coreIDsOnce.Do(func() {
+		for i := 0; ; i++ {
+			b, err := os.ReadFile("/sys/devices/system/cpu/cpu" + strconv.Itoa(i) + "/topology/core_id")
+			if err != nil {
+				break
+			}
+			id, err := strconv.Atoi(strings.TrimSpace(string(b)))
+			if err != nil {
+				break
+			}
+			coreIDsVal = append(coreIDsVal, id)
+		}
+	})
+	if len(coreIDsVal) < n {
+		return nil
+	}
+	return coreIDsVal[:n]
+}
+
 // ProcTable is the Processes tab payload.
 type ProcTable struct {
 	T         int64      `json:"t"`
@@ -1021,6 +1049,7 @@ type ProcTable struct {
 	CPUMHz    float64    `json:"cpu_mhz,omitempty"`
 	CPUMaxMHz float64    `json:"cpu_max_mhz,omitempty"`
 	CPUTemp   float64    `json:"cpu_temp,omitempty"`
+	CoreIDs   []int      `json:"core_ids,omitempty"` // for each logical CPU, the physical core it is a thread of (what the temperature sensors are named by)
 	Load      [3]float64 `json:"load"`
 	Mem       Mem        `json:"mem"`
 	Swap      Mem        `json:"swap"`
@@ -1204,6 +1233,7 @@ func (c *Collector) Processes() ProcTable {
 	if n := len(c.ring); n > 0 {
 		last := c.ring[n-1]
 		t.CPU, t.Cores, t.Net, t.CPUTemp = last.CPU, last.Cores, last.Net, cpuTemp(last.Temps)
+		t.CoreIDs = coreIDs(len(last.Cores))
 		from := n - 90
 		if from < 0 {
 			from = 0