feat: enable free page reporting

Balloon devices provide memory reclamation facilities through free page
reporting, as a more efficient mechanism (in terms of latency and CPU
time) than traditional ballooning.

Free page reporting instructs the guest to periodically report memory
that has been freed, so that we can reclaim it in the host side. It is
enabled before starting the sandbox and does not require any further
host-side orchestration.

This commit enables free page reporting unconditionally in our
sandboxes by setting up a balloon device configured to enable free page
reporting. Traditional ballooning is **not** used here.

Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>

Author: bchalios

packages/orchestrator/internal/sandbox/fc/client.go

@@ -296,6 +296,30 @@ func (c *apiClient) startVM(ctx context.Context) error {
 	return nil
 }
 
+func (c *apiClient) enableFreePageReporting(ctx context.Context) error {
+	ctx, span := tracer.Start(ctx, "enable-free-page-reporting")
+	defer span.End()
+
+	amountMib := int64(0)
+	deflateOnOom := false
+
+	balloonConfig := operations.PutBalloonParams{
+		Context: ctx,
+		Body: &models.Balloon{
+			AmountMib:         &amountMib,
+			DeflateOnOom:      &deflateOnOom,
+			FreePageReporting: true,
+		},
+	}
+
+	_, err := c.client.Operations.PutBalloon(&balloonConfig)
+	if err != nil {
+		return fmt.Errorf("error setting up balloon device: %w", err)
+	}
+
+	return nil
+}
+
 func (c *apiClient) memoryMapping(ctx context.Context) (*memory.Mapping, error) {
 	params := operations.GetMemoryMappingsParams{
 		Context: ctx,

packages/orchestrator/internal/sandbox/fc/process.go

@@ -343,6 +343,14 @@ func (p *Process) Create(
 	}
 	telemetry.ReportEvent(ctx, "set fc entropy config")
 
+	err = p.client.enableFreePageReporting(ctx)
+	if err != nil {
+		fcStopErr := p.Stop(ctx)
+
+		return errors.Join(fmt.Errorf("error enabling free page reporting: %w", err), fcStopErr)
+	}
+	telemetry.ReportEvent(ctx, "enabled free page reporting")
+
 	err = p.client.startVM(ctx)
 	if err != nil {
 		fcStopErr := p.Stop(ctx)