feat(perf): the performance page moves to the drawer, with ~/.cache

The island's performance icon and panel are gone: the drawer page covers
them. With only one host left, the panel drops its three-column grid for
one card per row at a larger size, since the page scrolls; temperatures
get a card of their own as tiles. The files move from island/perf to
modules/perf.

A cache card ports conky's: ~/.cache and its five largest children,
measured with du each time the page opens (28ms over 2 GiB here) rather
than read from conky's 15-minute sampler file. The largest is yellow,
red past half the total, as conky had it.

The warning dot now shows only on the drawer tile.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

11 files changed, 175 insertions, 156 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 863a7e5..fcdd1e9 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -14,7 +14,7 @@ modules.
     desktop/          the drawer (SUPER alone): sound, mail, VMs, status, performance,
                       clipboard, updates, appearance
       island/         top-centre pills on DP-1: clock, volume, tray, layout, privacy,
-                      calendar, performance
+                      calendar
     appearance/       wallpaper picker and colour scheme switcher
     window-switcher/  expose: open windows scattered as live previews, on ALT+TAB
                       or the top-right hot corner of DP-1
diff --git a/desktop/README.md b/desktop/README.md
index b0d3a2a..be22c48 100644
--- a/desktop/README.md
+++ b/desktop/README.md
@@ -33,7 +33,7 @@ the IPC layer rejects. The page-less grid entry is therefore the zero-argument
     modules/vm/          libvirt state, live stats, snapshots
     modules/appearance/  a tile that opens the separate appearance shell
     modules/ai/          local AI engines, start/stop for the apps using them
-    modules/perf/        the island's performance panel at drawer size
+    modules/perf/        CPU, temperatures, GPU, network, disks, ~/.cache
     modules/clipboard/   cliphist history: search, copy, delete, clear all
 
 Sound, mail, vm, network, bluetooth, kdeconnect and ai each carry their own README.
diff --git a/desktop/island/Island.qml b/desktop/island/Island.qml
index 1807c82..8532652 100644
--- a/desktop/island/Island.qml
+++ b/desktop/island/Island.qml
@@ -28,8 +28,8 @@ PanelWindow {
 
     screen: Quickshell.screens.find(s => s.name === "DP-1") ?? Quickshell.screens[0]
     anchors { top: true; left: true; right: true }
-    // Tall enough for the largest panel, the performance grid; the mask keeps
-    // everything outside the pills click-through.
+    // Tall enough for the largest panel; the mask keeps everything outside
+    // the pills click-through.
     implicitHeight: 480
     color: "transparent"
     exclusionMode: ExclusionMode.Ignore
@@ -38,7 +38,7 @@ PanelWindow {
     WlrLayershell.namespace: "quickshell-island"
     WlrLayershell.keyboardFocus: panel !== "" ? WlrKeyboardFocus.OnDemand : WlrKeyboardFocus.None
 
-    // "", "sound", "perf" or "calendar".
+    // "", "sound" or "calendar".
     property string panel: ""
 
     // --- reveal and hide -------------------------------------------------
@@ -212,6 +212,5 @@ PanelWindow {
         onMenuShown: win.menuHeld = true
         onOpenSound: win.panel = win.panel === "sound" ? "" : "sound"
         onOpenDrawer: { win.panel = ""; win.drawer.show("sound"); }
-        onOpenPerf: win.panel = win.panel === "perf" ? "" : "perf"
     }
 }
diff --git a/desktop/island/README.md b/desktop/island/README.md
index 4ad1050..c202e61 100644
--- a/desktop/island/README.md
+++ b/desktop/island/README.md
@@ -46,10 +46,10 @@ is open or not. Click opens the calendar panel.
 
 ## Status pill
 
-Left to right: performance icon, volume icon, tray, layout flag.
+Left to right: volume icon, tray, layout flag. The performance panel that
+used to open from here is the drawer's Performance page now
+(`desktop/modules/perf/`).
 
-- **Performance icon** opens the performance panel, see below. A dot on its
-  corner warns when something needs attention.
 - **Volume icon** shows the default sink (muted, low, medium, high). Click
   opens the sound panel.
 - **Tray** shows `SystemTray` items. Left click activates, right click opens
@@ -68,40 +68,6 @@ alone opens the drawer instead. `Prefs.qml` keeps only the pinned IP; a
 `controls` key left in `desktop.json` by the old panel is kept on write and
 otherwise ignored.
 
-## Performance panel
-
-The system monitor icon, first in the status pill, opens a card grid of the
-figures the conky dashboard used to show: CPU load with a bar per core, the
-CPU model, RAM and five temperatures; the Arc B580's temperatures, VRAM and
-fan (no utilisation, xe exposes none); download and upload over the last
-minute, the LAN address and the public IP; and the five mounts with their
-usage. `perf/Perf.qml` reads them; `perf/Perf.js` holds the parsing, tested by
-`node desktop/island/perf/test_perf.js`.
-
-A dot on the icon shows the worst of these, yellow or red:
-
-| Input | Yellow | Red |
-| --- | --- | --- |
-| each temperature | its warn | its crit |
-| RAM | 85% | 95% |
-| each disk | 90% | 95% |
-| public IP | | differs from the pinned one |
-
-CPU load is left out, since spikes would flicker it. There is no hysteresis,
-so a sensor sitting on its threshold can toggle the dot. The pin beside the
-public IP stores the address shown as `perf.pinnedIp` in
-`$XDG_STATE_HOME/quickshell/desktop.json`; the check exists because the VPN
-into the LAN depends on the ISP's fixed address. The fetch is
-`curl -4 https://ipinfo.io/ip` every 30 minutes from the last attempt, into
-`~/.cache/udt/pubip.txt`, the file conky's sampler used. A failed fetch is
-never a mismatch: the old value goes stale after 4 hours and shows as a dash.
-
-CPU, RAM, temperatures and disks are sampled always, so the dot works with
-the panel closed. Per-core load, the network rate, VRAM (a scan of every
-fdinfo, ~14ms) and the fan run only while the panel is open, and the panel
-itself is loaded only then. The mount list, `br0`, the GPU name and the
-12 GiB VRAM size are constants in `Perf.qml`.
-
 ## Calendar panel
 
 The clock pill opens a month grid beside the selected day's agenda. Dots
diff --git a/desktop/island/StatusPill.qml b/desktop/island/StatusPill.qml
index 953b713..2202747 100644
--- a/desktop/island/StatusPill.qml
+++ b/desktop/island/StatusPill.qml
@@ -14,13 +14,11 @@ import Quickshell.Widgets
 import Quickshell.Services.SystemTray
 import QtQuick
 import ".."
-import "perf"
 import "Logic.js" as Logic
 
-// Performance icon, volume icon, tray, layout flag. The performance and
-// volume icons open their panels in this capsule;
-// the tray is a plain tray; the flag switches layout on scroll and ignores
-// clicks.
+// Volume icon, tray, layout flag. The volume icon opens its panel in this
+// capsule; the tray is a plain tray; the flag switches layout on scroll and
+// ignores clicks.
 Capsule {
     id: pill
 
@@ -30,16 +28,14 @@ Capsule {
     property string panel: ""
 
     signal openSound()
-    signal openPerf()
     signal openDrawer()
     // Emitted just before a tray menu opens; the menu cannot report its close.
     signal menuShown()
 
-    expanded: panel === "sound" || panel === "perf"
+    expanded: panel === "sound"
     restWidth: restRow.implicitWidth + 24
-    panelWidth: panel === "perf" ? 600 : 320
-    panelHeight: (panel === "perf" ? (perfPanel.item ? perfPanel.item.implicitHeight : 0)
-                : soundPanel.implicitHeight) + 28
+    panelWidth: 320
+    panelHeight: soundPanel.implicitHeight + 28
 
 
     Row {
@@ -50,36 +46,6 @@ Capsule {
         visible: opacity > 0
         Behavior on opacity { NumberAnimation { duration: 120 } }
 
-        // The worst severity as a dot on the corner: IconImage cannot be
-        // recoloured without an effect layer. Never the accent (AGENTS.md).
-        Item {
-            anchors.verticalCenter: parent.verticalCenter
-            width: 18
-            height: 18
-
-            IconImage {
-                anchors.fill: parent
-                source: Quickshell.iconPath("utilities-system-monitor", true)
-            }
-
-            Rectangle {
-                anchors { right: parent.right; top: parent.top; rightMargin: -2; topMargin: -2 }
-                width: 8
-                height: 8
-                radius: 4
-                visible: Perf.severity !== "ok"
-                color: Perf.severity === "crit" ? Theme.red : Theme.yellow
-                border.width: 1
-                border.color: Theme.base
-            }
-
-            MouseArea {
-                anchors.fill: parent
-                cursorShape: Qt.PointingHandCursor
-                onClicked: pill.openPerf()
-            }
-        }
-
         IconImage {
             anchors.verticalCenter: parent.verticalCenter
             implicitSize: 18
@@ -156,15 +122,4 @@ Capsule {
         Behavior on opacity { NumberAnimation { duration: 160 } }
         onOpenDrawer: pill.openDrawer()
     }
-
-    // Loaded only while open: its models are fresh arrays every sample, and
-    // a hidden instance would rebuild its rows every 2s for the whole session.
-    Loader {
-        id: perfPanel
-        x: 14
-        y: 14
-        width: 600 - 28
-        active: pill.panel === "perf"
-        sourceComponent: PerfPanel { width: 600 - 28 }
-    }
 }
diff --git a/desktop/modules/perf/Perf.js b/desktop/modules/perf/Perf.js
index b853f50..d84c694 100644
--- a/desktop/modules/perf/Perf.js
+++ b/desktop/modules/perf/Perf.js
@@ -72,6 +72,20 @@ function df(text) {
     return out;
 }
 
+// `du -B1 -d1 <dir>`: {total, items} with items largest first by basename,
+// or null when du printed nothing. du prints the directory itself last, and
+// it is also the largest line, so the total is the maximum.
+function du(text) {
+    const rows = [];
+    for (const line of text.split("\n")) {
+        const m = /^(\d+)\t(.*)$/.exec(line);
+        if (m) rows.push({ name: m[2].replace(/.*\//, ""), bytes: Number(m[1]) });
+    }
+    if (!rows.length) return null;
+    rows.sort((x, y) => y.bytes - x.bytes);
+    return { total: rows[0].bytes, items: rows.slice(1) };
+}
+
 // VRAM in bytes from the fdinfo scan: drm-resident-vram0 of every xe fd,
 // counted once per drm-client-id because a client holds several fds.
 function vram(text) {
diff --git a/desktop/modules/perf/Perf.qml b/desktop/modules/perf/Perf.qml
index 53d8670..6216959 100644
--- a/desktop/modules/perf/Perf.qml
+++ b/desktop/modules/perf/Perf.qml
@@ -21,7 +21,7 @@ import "Perf.js" as P
 // The numbers behind the performance panel and the status pill's icon. CPU,
 // RAM, temperatures and disks are sampled always, so the icon can warn while
 // the panel is closed; per-core load, the network rate, VRAM and the fan only
-// while `detailed`, which is any PerfPanel existing (island or drawer).
+// while `detailed`, which is any PerfPanel existing (the drawer page).
 // /proc and /sys are FileViews reloaded on a timer, no subprocess; df, the
 // fdinfo scan, ip and curl are Processes.
 Singleton {
diff --git a/desktop/modules/perf/PerfModule.qml b/desktop/modules/perf/PerfModule.qml
index d0ddf35..e596f9a 100644
--- a/desktop/modules/perf/PerfModule.qml
+++ b/desktop/modules/perf/PerfModule.qml
@@ -11,11 +11,9 @@
 
 import QtQuick
 import "../.."
-import "../../island/perf"
 
-// The island's performance panel at drawer size. Perf.qml stays in
-// island/perf and is shared: its always-on sampling already runs for the
-// island's warning dot, so this module adds no service of its own.
+// The figures the conky dashboard used to show, as a scrolling page. Perf.qml
+// samples them; the tile's dot is its severity.
 Module {
     id: mod
 
@@ -38,7 +36,7 @@ Module {
                     + " · RAM " + (Perf.mem ? Math.round(100 * Perf.mem.used / Perf.mem.total) + "%" : "--")
             }
 
-            // The same dot as the island icon. Never the accent (AGENTS.md).
+            // The worst severity. Never the accent (AGENTS.md).
             Rectangle {
                 anchors.verticalCenter: parent.verticalCenter
                 width: 8
diff --git a/desktop/modules/perf/PerfPanel.qml b/desktop/modules/perf/PerfPanel.qml
index f149d82..de9021b 100644
--- a/desktop/modules/perf/PerfPanel.qml
+++ b/desktop/modules/perf/PerfPanel.qml
@@ -10,24 +10,21 @@
 // GNU General Public License for more details.
 
 import Quickshell
+import Quickshell.Io
 import QtQuick
-import QtQuick.Layouts
 import "../.."
 import "Perf.js" as P
 
-// CPU, GPU, network and disks as cards in three columns: CPU down the left,
-// GPU and network beside it, disks under those two. Numbers come from Perf;
-// colours follow conky's bands, so they read as they did there.
-GridLayout {
+// CPU, temperatures, GPU, network, disks and ~/.cache as cards, one per row:
+// the drawer page scrolls, so nothing has to share a line. Numbers come from
+// Perf; colours follow conky's bands, so they read as they did there.
+Column {
     id: panel
 
-    columns: 3
-    columnSpacing: 8
-    rowSpacing: 8
+    spacing: 12
 
-    readonly property real col: (width - 2 * columnSpacing) / 3
+    readonly property int fs: Theme.fontSize - 2
     readonly property var gpuTemp: sensor("GPU")
-    readonly property var vramTemp: sensor("VRAM")
 
     function tone(v, warn, crit) {
         const b = P.band(v, warn, crit);
@@ -37,10 +34,8 @@ GridLayout {
     function sensor(label) {
         return Perf.temps.find(t => t.label === label) || { value: null, warn: 0, crit: 0 };
     }
-    // Detailed sampling (per-core, network, VRAM, fan) runs while any panel
-    // exists. The island loads one only while open and the drawer page only
-    // while shown, so counting instances is the whole gate, and two of them
-    // never clear it under each other.
+    // Detailed sampling (per-core, network, VRAM, fan) runs while the panel
+    // exists, which is while the drawer page is shown.
     Component.onCompleted: Perf.viewers++
     Component.onDestruction: Perf.viewers--
 
@@ -53,7 +48,7 @@ GridLayout {
     }
 
     component Label: Text {
-        font { family: Theme.fontFamily; pixelSize: Theme.fontSize - 4 }
+        font { family: Theme.fontFamily; pixelSize: panel.fs }
         color: Theme.text
     }
 
@@ -72,7 +67,7 @@ GridLayout {
             Text {
                 visible: text !== ""
                 text: parent.parent.glyph
-                font { family: Theme.iconFamily; pixelSize: Theme.fontSize - 2 }
+                font { family: Theme.iconFamily; pixelSize: panel.fs + 2 }
                 color: parent.parent.labelColor
             }
             Label { text: parent.parent.label; color: parent.parent.labelColor }
@@ -89,7 +84,7 @@ GridLayout {
         property real frac: 0
         property color fill: Theme.green
         width: parent ? parent.width : 0
-        height: 5
+        height: 6
         radius: 3
         color: Theme.surfaceAlt
         Rectangle {
@@ -105,17 +100,17 @@ GridLayout {
         property string title: ""
         property string headline: ""
         property color headlineColor: Theme.text
+        width: panel.width
         radius: 10
         color: Qt.alpha(Theme.surface, 0.6)
-        implicitHeight: body.implicitHeight + 20
-        Layout.fillHeight: true
+        implicitHeight: body.implicitHeight + 28
 
         Column {
             id: body
-            x: 10
-            y: 10
-            width: parent.width - 20
-            spacing: 5
+            x: 14
+            y: 14
+            width: parent.width - 28
+            spacing: 8
 
             Item {
                 width: parent.width
@@ -124,7 +119,7 @@ GridLayout {
                     id: titleText
                     anchors.verticalCenter: parent.verticalCenter
                     text: parent.parent.parent.title
-                    font { family: Theme.fontFamily; pixelSize: Theme.fontSize - 4; bold: true }
+                    font { family: Theme.fontFamily; pixelSize: panel.fs; bold: true }
                     color: Theme.subtext
                 }
                 Text {
@@ -141,10 +136,6 @@ GridLayout {
     // --- CPU ----------------------------------------------------------------
 
     Card {
-        Layout.row: 0
-        Layout.column: 0
-        Layout.rowSpan: 2
-        Layout.preferredWidth: panel.col
         title: "CPU"
         headline: Perf.load === null ? "--" : Math.round(Perf.load) + "%"
         headlineColor: panel.tone(Perf.load, 25, 75)
@@ -160,7 +151,7 @@ GridLayout {
         Row {
             id: eq
             width: parent.width
-            height: 40
+            height: 64
             spacing: 2
             Repeater {
                 model: Perf.cores
@@ -187,14 +178,42 @@ GridLayout {
             frac: Perf.mem ? Perf.mem.used / Perf.mem.total : 0
             fill: panel.tone(panel.pct(Perf.mem ? Perf.mem.used : null, Perf.mem ? Perf.mem.total : 0), 25, 75)
         }
+    }
 
-        Repeater {
-            model: Perf.temps.filter(t => t.label !== "GPU" && t.label !== "VRAM")
-            delegate: Pair {
-                required property var modelData
-                label: modelData.label
-                value: panel.deg(modelData.value)
-                valueColor: panel.tone(modelData.value, modelData.warn, modelData.crit)
+    // --- temperatures -------------------------------------------------------
+
+    Card {
+        title: "TEMPERATURES"
+
+        Flow {
+            id: temps
+            width: parent.width
+            spacing: 8
+            Repeater {
+                model: Perf.temps
+                delegate: Rectangle {
+                    required property var modelData
+                    width: (temps.width - 3 * temps.spacing) / 4
+                    height: tempCol.implicitHeight + 16
+                    radius: 8
+                    color: Qt.alpha(Theme.surfaceAlt, 0.5)
+                    Column {
+                        id: tempCol
+                        anchors.centerIn: parent
+                        spacing: 2
+                        Label {
+                            anchors.horizontalCenter: parent.horizontalCenter
+                            text: modelData.label
+                            color: Theme.subtext
+                        }
+                        Text {
+                            anchors.horizontalCenter: parent.horizontalCenter
+                            text: panel.deg(modelData.value)
+                            font { family: Theme.fontFamily; pixelSize: panel.fs + 6; bold: true }
+                            color: panel.tone(modelData.value, modelData.warn, modelData.crit)
+                        }
+                    }
+                }
             }
         }
     }
@@ -203,9 +222,6 @@ GridLayout {
 
     // No utilisation: xe exposes no busy percentage.
     Card {
-        Layout.row: 0
-        Layout.column: 1
-        Layout.preferredWidth: panel.col
         title: "GPU · " + Perf.gpuName
         headline: panel.deg(panel.gpuTemp.value)
         headlineColor: panel.tone(panel.gpuTemp.value, panel.gpuTemp.warn, panel.gpuTemp.crit)
@@ -219,11 +235,6 @@ GridLayout {
             fill: panel.tone(panel.pct(Perf.vram, Perf.vramTotal), 25, 75)
         }
         Pair {
-            label: "VRAM temp"
-            value: panel.deg(panel.vramTemp.value)
-            valueColor: panel.tone(panel.vramTemp.value, panel.vramTemp.warn, panel.vramTemp.crit)
-        }
-        Pair {
             label: "Fan"
             value: Perf.fan === null ? "--" : Perf.fan + " rpm"
         }
@@ -232,15 +243,12 @@ GridLayout {
     // --- network ------------------------------------------------------------
 
     Card {
-        Layout.row: 0
-        Layout.column: 2
-        Layout.preferredWidth: panel.col
         title: "NET · " + Perf.iface
 
         Canvas {
             id: graph
             width: parent.width
-            height: 44
+            height: 80
             onPaint: {
                 const ctx = getContext("2d");
                 ctx.reset();
@@ -291,7 +299,7 @@ GridLayout {
                 id: pin
                 anchors { right: parent.right; verticalCenter: pubText.verticalCenter }
                 text: String.fromCodePoint(0xF0403)
-                font { family: Theme.iconFamily; pixelSize: Theme.fontSize - 2 }
+                font { family: Theme.iconFamily; pixelSize: panel.fs + 2 }
                 color: Perf.ip.ip !== "" && Perf.ip.ip === Prefs.pinnedIp ? Theme.text : Theme.overlay
 
                 MouseArea {
@@ -308,10 +316,6 @@ GridLayout {
     // --- disks --------------------------------------------------------------
 
     Card {
-        Layout.row: 1
-        Layout.column: 1
-        Layout.columnSpan: 2
-        Layout.preferredWidth: 2 * panel.col + panel.columnSpacing
         title: "DISKS"
 
         Repeater {
@@ -319,7 +323,7 @@ GridLayout {
             delegate: Column {
                 required property var modelData
                 width: parent.width
-                spacing: 2
+                spacing: 4
                 Pair {
                     glyph: panel.glyph(modelData)
                     label: modelData.host || modelData.mount
@@ -333,4 +337,45 @@ GridLayout {
             }
         }
     }
+
+    // --- cache --------------------------------------------------------------
+
+    // ~/.cache and its five largest children, measured once per page open:
+    // du over the tree took 28ms, so conky's 15-minute sampler file is not
+    // needed. The largest is coloured by its share of the total, as conky
+    // did, so the eye lands on the one worth deleting.
+    property var cache: null    // {total, items: [{name, bytes}]}
+
+    Process {
+        running: true
+        command: ["du", "-B1", "-d1", (Quickshell.env("XDG_CACHE_HOME") || Quickshell.env("HOME") + "/.cache")]
+        stdout: StdioCollector {
+            onStreamFinished: panel.cache = P.du(text)
+        }
+    }
+
+    Card {
+        title: "CACHE"
+        headline: panel.cache ? P.bytes(panel.cache.total) : "--"
+
+        Repeater {
+            model: panel.cache ? panel.cache.items.slice(0, 5) : []
+            delegate: Column {
+                required property var modelData
+                required property int index
+                readonly property real share: modelData.bytes / panel.cache.total
+                width: parent.width
+                spacing: 4
+                Pair {
+                    label: modelData.name
+                    value: P.bytes(modelData.bytes)
+                    valueColor: index === 0 ? (share > 0.5 ? Theme.red : Theme.yellow) : Theme.text
+                }
+                Bar {
+                    frac: share
+                    fill: index === 0 ? (share > 0.5 ? Theme.red : Theme.yellow) : Theme.overlay
+                }
+            }
+        }
+    }
 }
diff --git a/desktop/modules/perf/README.md b/desktop/modules/perf/README.md
new file mode 100644
index 0000000..dea5a7e
--- /dev/null
+++ b/desktop/modules/perf/README.md
@@ -0,0 +1,36 @@
+# perf
+
+The figures the conky dashboard used to show, as a drawer page of cards, one
+per row; the page scrolls. CPU load with a bar per core, the CPU model and
+RAM; every temperature as a tile; the Arc B580's VRAM and fan (no
+utilisation, xe exposes none); download and upload over the last minute, the
+LAN address and the public IP; the five mounts with their usage; and
+`~/.cache` with its five largest children. `Perf.qml` reads them; `Perf.js`
+holds the parsing, tested by `node desktop/modules/perf/test_perf.js`.
+
+The tile shows CPU and RAM, and a dot for the worst of these, yellow or red:
+
+| Input | Yellow | Red |
+| --- | --- | --- |
+| each temperature | its warn | its crit |
+| RAM | 85% | 95% |
+| each disk | 90% | 95% |
+| public IP | | differs from the pinned one |
+
+CPU load is left out, since spikes would flicker it. There is no hysteresis,
+so a sensor sitting on its threshold can toggle the dot. The pin beside the
+public IP stores the address shown as `perf.pinnedIp` in
+`$XDG_STATE_HOME/quickshell/desktop.json`; the check exists because the VPN
+into the LAN depends on the ISP's fixed address. The fetch is
+`curl -4 https://ipinfo.io/ip` every 30 minutes from the last attempt, into
+`~/.cache/udt/pubip.txt`, the file conky's sampler used. A failed fetch is
+never a mismatch: the old value goes stale after 4 hours and shows as a dash.
+
+CPU, RAM, temperatures and disks are sampled always. Per-core load, the
+network rate, VRAM (a scan of every fdinfo, ~14ms) and the fan run only while
+the page is open. The mount list, `br0`, the GPU name and the 12 GiB VRAM
+size are constants in `Perf.qml`.
+
+The cache card runs `du -B1 -d1` once each time the page opens, 28ms over
+2 GiB, instead of reading conky's 15-minute `cachesize.txt`. The largest
+child is yellow, red when it holds over half the total, as conky had it.
diff --git a/desktop/modules/perf/test_perf.js b/desktop/modules/perf/test_perf.js
index 5f39f5d..ac5859d 100644
--- a/desktop/modules/perf/test_perf.js
+++ b/desktop/modules/perf/test_perf.js
@@ -9,7 +9,7 @@
 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 // GNU General Public License for more details.
 
-// Run: node desktop/island/perf/test_perf.js
+// Run: node desktop/modules/perf/test_perf.js
 // Perf.js is a QML library, so its .pragma line is stripped before node
 // evaluates it, as test_controls.js does for Controls.js.
 
@@ -19,7 +19,7 @@ const assert = require("assert");
 const src = fs.readFileSync(__dirname + "/Perf.js", "utf8")
     .replace(/^\.pragma library$/m, "");
 const P = new Function(src + "\nreturn { cpuTimes, load, meminfo, df, vram, rate, " +
-    "hwmonMap, lanAddr, cpuModel, band, worst, isIPv4, parsePubip, formatPubip, " +
+    "hwmonMap, lanAddr, cpuModel, du, band, worst, isIPv4, parsePubip, formatPubip, " +
     "ipCheck, due, push, bytes, speed };")();
 
 // cpuTimes: aggregate first, then cores; idle is idle + iowait.
@@ -150,4 +150,10 @@ assert.strictEqual(P.bytes(null), "--");
 assert.strictEqual(P.speed(1024 * 1024 * 1.2), "1.2M/s");
 assert.strictEqual(P.speed(null), "--");
 
+// du: total is the directory's own (largest) line; children largest first.
+const cache = P.du("5\t/c/b\n9\t/c/a b\n20\t/c\n");
+assert.strictEqual(cache.total, 20);
+assert.deepStrictEqual(cache.items, [{ name: "a b", bytes: 9 }, { name: "b", bytes: 5 }]);
+assert.strictEqual(P.du(""), null);
+
 console.log("test_perf: ok");