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>

PLAN.md

@@ -331,7 +331,7 @@ something long in one, switch away and back, refresh — it's all still there.
   the top, not a partition: the scan covers every filesystem the disk backs — its partitions'
   mountpoints, and for a disk in a ZFS pool every mounted dataset of the pool (any of `tank`'s
   eight disks shows `tank`). The walk runs as a helper process, `hamlab space-walk <roots>`,
-  as root through `priv` when the host allows (so `/var/lib/docker` and `/root` count), 16
+  as root through `priv` when the host allows (so `/var/lib/docker` and `/root` count), 32
   workers reading directories depth-first, never crossing a filesystem boundary by itself;
   each root is grafted into one tree at its path. Files under 128 KiB are not kept one by one
   but summed per folder as "N smaller files" — what keeps a scan of millions of files to tens

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

internal/space/walk.go

@@ -100,7 +100,7 @@ func Walk(ctx context.Context, roots []string, progress func(Progress)) (*Node,
 	if len(trees) == 0 {
 		return root, os.ErrNotExist
 	}
-	workers := 16
+	workers := 32
 	var wg sync.WaitGroup
 	for i := 0; i < workers; i++ {
 		wg.Add(1)

web/src/Top.tsx

@@ -309,9 +309,12 @@ export default function Top() {
   // "11th Gen Intel(R) Core(TM) i7-11700T @ 1.40GHz" is a whole line of border to itself; the
   // clock is already beside it, and the generation is in the model number
   const model = (pt?.cpu_model ?? '').replace(/\(R\)|\(TM\)|CPU|Processor/g, '').replace(/@.*$/, '').replace(/^\d+th Gen\s*/i, '').replace(/\s+/g, ' ').trim()
-  // the hottest thing that looks like a CPU sensor, and one per core where the chip names them
-  const coreTemp = (i: number) => s?.temps.find((t) => new RegExp(`core ${i}\\b`, 'i').test(t.label))?.c
+  // the hottest thing that looks like a CPU sensor, and one per core where the chip names them;
+  // a second thread of a core (CPU 8 on an 8-core chip with hyper-threading) wears its core's
+  const coreTemp = (i: number) => { const id = pt?.core_ids?.[i] ?? i; return s?.temps.find((t) => new RegExp(`core ${id}\\b`, 'i').test(t.label))?.c }
   const cpuTemp = pt?.cpu_temp ?? s?.temps.find((t) => /package|tctl|tdie|cpu/i.test(t.label))?.c ?? coreTemp(0)
+  // the temperature columns are there for every row once any row has one, so the % column lines up
+  const anyTemp = cpuTemp !== undefined || cores.some((_, i) => coreTemp(i) !== undefined)
   const cached = (mem as { cached?: number }).cached ?? 0
   const free = (mem as { free?: number }).free ?? Math.max(0, mem.total - mem.used - cached)
   const swap = s?.swap ?? pt?.swap
@@ -344,16 +347,16 @@ export default function Top() {
               <span className="t-core-n">CPU</span>
               <Meter pct={cpu} grad="cpu" />
               <span className="t-core-p">{Math.round(cpu)}%</span>
-              {cpuTemp !== undefined && <><span className="t-core-t"><Meter pct={Math.min(100, (cpuTemp / 100) * 100)} grad="temp" /></span><span className="t-core-c">{Math.round(cpuTemp)}°C</span></>}
+              {anyTemp && <><span className="t-core-t">{cpuTemp !== undefined && <Meter pct={Math.min(100, (cpuTemp / 100) * 100)} grad="temp" />}</span><span className="t-core-c">{cpuTemp !== undefined ? `${Math.round(cpuTemp)}°C` : ''}</span></>}
             </div>
             {cores.map((v, i) => {
               const t = coreTemp(i)
               return (
                 <div className="t-core" key={i}>
                   <span className="t-core-n">C{i}</span>
-                  <span className="t-core-g" title={`core ${i}`}>{braille(curves.get(`cpu.core.${i}.usage`) ?? [], 9)}</span>
+                  <span className="t-core-g" title={pt?.core_ids && pt.core_ids[i] !== i ? `cpu ${i} · a thread of core ${pt.core_ids[i]}` : `core ${i}`}>{braille(curves.get(`cpu.core.${i}.usage`) ?? [], 9)}</span>
                   <span className="t-core-p">{Math.round(v)}%</span>
-                  {t !== undefined && <><span className="t-core-t"><Meter pct={Math.min(100, t)} grad="temp" /></span><span className="t-core-c">{Math.round(t)}°C</span></>}
+                  {anyTemp && <><span className="t-core-t">{t !== undefined && <Meter pct={Math.min(100, t)} grad="temp" />}</span><span className="t-core-c">{t !== undefined ? `${Math.round(t)}°C` : ''}</span></>}
                 </div>
               )
             })}

web/src/api.ts

@@ -73,7 +73,7 @@ export interface FS { mount: string; type: string; size: number; used: number }
 export interface UPS { driver: string; model: string; state: string; source: string; on_battery: boolean; in_v: number; out_v: number; battery_pct: number; runtime_min: number; load_w: number; load_pct: number; last_event?: string }
 export interface Proc { pid: number; ppid: number; name: string; cmd?: string; user: string; cpu: number; cpu_time: number; rss: number; threads: number; state: string; nice: number; started: number }
 export interface MemInfo { total: number; used: number; avail: number; free?: number; cached?: number; buffers?: number }
-export interface ProcTable { t: number; cpu: number; cores: number[]; cpu_hist: number[]; cpu_model?: string; cpu_mhz?: number; cpu_max_mhz?: number; cpu_temp?: number; load: [number, number, number]; mem: MemInfo; swap: MemInfo; net: NetIf[]; uptime: number; procs: Proc[]; total: number; running: number }
+export interface ProcTable { t: number; cpu: number; cores: number[]; cpu_hist: number[]; cpu_model?: string; cpu_mhz?: number; cpu_max_mhz?: number; cpu_temp?: number; core_ids?: number[]; load: [number, number, number]; mem: MemInfo; swap: MemInfo; net: NetIf[]; uptime: number; procs: Proc[]; total: number; running: number }
 export interface Sample {
   t: number; interval_ms: number; cpu: number; cores: number[]; load: [number, number, number]
   mem: { total: number; used: number; avail: number }; swap: { total: number; used: number; avail: number }