Reduce host capacity headroom and remove learned usage padding

src/lib/server/hosts/calibration.ts

@@ -4,7 +4,6 @@ import type { CapacityCalibration, CapacitySample, CapacitySamplePage, HostInven
 
 const BOOTSTRAP_CPU = 0.5;
 const BOOTSTRAP_MEMORY = 1024 ** 3;
-const MARGIN = 1.25;
 const WINDOW_MS = 24 * 60 * 60_000;
 const MAX_SAMPLES = 10_000;
 type Phase = 'startup' | 'running';
@@ -83,8 +82,8 @@ export function recordInstanceResources(hostId: string, inventory: HostInventory
                 .all(...(scope === '*' ? [] : [scope]), phase, new Date(Date.parse(timestamp) - WINDOW_MS).toISOString(), MAX_SAMPLES) as
                 { cpu_cores: number; memory_bytes: number; bucket: string }[];
             const percentile = (values: number[]) => values.sort((a, b) => a - b)[phase === 'startup' ? values.length - 1 : Math.ceil(values.length * 0.95) - 1];
-            const cpu = Math.max(percentile(rows.map(row => row.cpu_cores)), peak.cpu) * MARGIN;
-            const memory = Math.ceil(Math.max(percentile(rows.map(row => row.memory_bytes)), peak.memory) * MARGIN);
+            const cpu = Math.max(percentile(rows.map(row => row.cpu_cores)), peak.cpu);
+            const memory = Math.ceil(Math.max(percentile(rows.map(row => row.memory_bytes)), peak.memory));
             handle.prepare(`INSERT INTO ec_resource_allowances
                 (scope,phase,cpu_cores,memory_bytes,samples,window_start,observed_at,computed_at) VALUES(?,?,?,?,?,?,?,?) ON CONFLICT(scope,phase) DO UPDATE SET
                 cpu_cores=excluded.cpu_cores,memory_bytes=excluded.memory_bytes,samples=excluded.samples,
@@ -96,7 +95,7 @@ export function recordInstanceResources(hostId: string, inventory: HostInventory
             // Raise the allowance immediately on a new peak; a lower sample
             // cannot reduce it until the next scheduled percentile calculation.
             handle.prepare(`UPDATE ec_resource_allowances SET cpu_cores=MAX(cpu_cores,?),memory_bytes=MAX(memory_bytes,?),observed_at=? WHERE scope=? AND phase=?`)
-                .run(peak.cpu * MARGIN, Math.ceil(peak.memory * MARGIN), timestamp, scope, phase);
+                .run(peak.cpu, Math.ceil(peak.memory), timestamp, scope, phase);
         }
     }
 }

src/lib/server/hosts/capacity.ts

@@ -6,7 +6,8 @@ import { capacityCalibration } from './calibration.js';
 
 // Storage and OS headroom are separate from learned instance CPU/memory usage.
 const INSTANCE_STORAGE_BYTES = 1024 ** 3;
-const MEMORY_HEADROOM = 512 * 1024 ** 2;
+const MEMORY_HEADROOM = 500_000_000;
+const CPU_USABLE_FRACTION = 0.95;
 export class CapacityError extends Error {}
 export interface PlacementOptions {
     hostId?: string; libraryId: string; image: string; bindAddress?: string;
@@ -83,7 +84,7 @@ function projectedLoad(host: Host, options: PlacementOptions): number {
     const memory = Math.max(usedMemory + extraMemory, reservedMemory);
     const usableMemory = memoryTotal - MEMORY_HEADROOM;
     const gib = (bytes: number) => `${(bytes / 1024 ** 3).toFixed(2)} GiB`;
-    if (cores > cpuCount * 0.9) throw new Error(`Insufficient CPU capacity: ${cores.toFixed(2)} cores projected, ${(cpuCount * 0.9).toFixed(2)} usable; ${reservations} reservations including this launch.`);
+    if (cores > cpuCount * CPU_USABLE_FRACTION) throw new Error(`Insufficient CPU capacity: ${cores.toFixed(2)} cores projected, ${(cpuCount * CPU_USABLE_FRACTION).toFixed(2)} usable; ${reservations} reservations including this launch.`);
     if (memory > usableMemory) throw new Error(`Insufficient memory capacity: ${gib(memory)} projected, ${gib(usableMemory)} usable after host headroom. `
         + `${gib(usedMemory)} currently used + ${gib(extraMemory)} additional reservations; ${reservations} reservations including this launch (${gib(startup.memoryBytes)} startup allowance).`);
     // Recovered resources must not remain unavailable until the historical

src/lib/server/hosts/schema.ts

@@ -57,6 +57,7 @@ export function ensureHostSchema(handle: Database.Database): void {
         CREATE TABLE IF NOT EXISTS ec_resource_allowances (
             scope TEXT NOT NULL, phase TEXT NOT NULL, cpu_cores REAL NOT NULL, memory_bytes REAL NOT NULL,
             samples INTEGER NOT NULL, window_start TEXT NOT NULL, observed_at TEXT NOT NULL, computed_at TEXT NOT NULL,
+            usage_margin REAL NOT NULL DEFAULT 1,
             PRIMARY KEY(scope,phase)
         );
         CREATE TABLE IF NOT EXISTS ec_host_decommissions (
@@ -71,5 +72,14 @@ export function ensureHostSchema(handle: Database.Database): void {
     if (!columns.some(column => column.name === 'last_delivered_at')) handle.exec('ALTER TABLE ec_host_operations ADD COLUMN last_delivered_at TEXT');
     const hostColumns = handle.prepare('PRAGMA table_info(ec_hosts)').all() as { name: string }[];
     if (!hostColumns.some(column => column.name === 'deleted_at')) handle.exec('ALTER TABLE ec_hosts ADD COLUMN deleted_at TEXT');
+    const allowanceColumns = handle.prepare('PRAGMA table_info(ec_resource_allowances)').all() as { name: string }[];
+    if (!allowanceColumns.some(column => column.name === 'usage_margin')) {
+        // Existing caches include 25% padding. Preserve learned evidence while
+        // removing that padding exactly once, including dormant startup models.
+        handle.transaction(() => {
+            handle.exec('ALTER TABLE ec_resource_allowances ADD COLUMN usage_margin REAL NOT NULL DEFAULT 1');
+            handle.exec('UPDATE ec_resource_allowances SET cpu_cores=cpu_cores/1.25, memory_bytes=CAST(memory_bytes/1.25 AS INTEGER)');
+        })();
+    }
     initialized.add(handle);
 }

src/lib/ui/components/CapacitySamples.svelte

@@ -37,7 +37,7 @@
 <details bind:open>
     <summary>View samples</summary>
     {#if open}
-        <p>Retained minute peaks from the last 24 hours, before the 25% allowance headroom. CPU and memory peaks may come from different heartbeats. Choose the fleet to inspect measurements from other hosts used by fleet allowances.</p>
+        <p>Retained minute peaks from the last 24 hours, used without extra allowance padding. CPU and memory peaks may come from different heartbeats. Choose the fleet to inspect measurements from other hosts used by fleet allowances.</p>
         <div class="controls">
             <label>Source<select bind:value={scope} onchange={() => page = 1}><option value="host">This host</option><option value="fleet">Entire fleet</option></select></label>
             <label>Phase<select bind:value={phase} onchange={() => page = 1}><option value="all">All phases</option><option value="startup">Starting</option><option value="running">Running</option></select></label>