mempool init/fini on the warm/cold events for the first/last instance.

src/tests/00basic.vtc

@@ -35,6 +35,20 @@ varnish v1 -expect MEMPOOL.pesi.pool > 0
 varnish v1 -expect MEMPOOL.pesi.sz_wanted > 0
 varnish v1 -expect MEMPOOL.pesi.sz_actual > 0
 
+varnish v1 -cli "vcl.state vcl2 cold"
+
+varnish v1 -vsc MEMPOOL.pesi.*
+varnish v1 -expect MEMPOOL.pesi.pool > 0
+varnish v1 -expect MEMPOOL.pesi.sz_wanted > 0
+varnish v1 -expect MEMPOOL.pesi.sz_actual > 0
+
+varnish v1 -cli "vcl.state vcl2 warm"
+
+varnish v1 -vsc MEMPOOL.pesi.*
+varnish v1 -expect MEMPOOL.pesi.pool > 0
+varnish v1 -expect MEMPOOL.pesi.sz_wanted > 0
+varnish v1 -expect MEMPOOL.pesi.sz_actual > 0
+
 varnish v1 -cli "vcl.show vcl1"
 varnish v1 -cli "vcl.use vcl2"
 varnish v1 -cli "vcl.discard vcl1"

src/vdp_pesi.c

@@ -285,7 +285,7 @@ fini_data(struct req *req, struct node *node);
 
 
 /* shared object globals */
-static unsigned loadcnt = 0;
+static unsigned loadcnt = 0, warmcnt = 0;
 static struct VSC_lck *lck_bytes_tree, *lck_pesi_tree;
 static struct vsc_seg  *vsc_seg = NULL;
 static struct mempool *mempool = NULL;
@@ -2625,27 +2625,36 @@ vmod_event(VRT_CTX, struct vmod_priv *priv, enum vcl_event_e e)
 			    "pesi.pesi_tree");
 			AN(lck_bytes_tree);
 			AN(lck_pesi_tree);
-			AZ(mempool);
-			mempool = mpl_init();
-			AN(mempool);
 		}
 
 		VRT_AddVDP(ctx, &VDP_pesi);
-		return (0);
+		break;
 	case VCL_EVENT_DISCARD:
 		VRT_RemoveVDP(ctx, &VDP_pesi);
 
 		AN(loadcnt);
-		if (--loadcnt == 0) {
+		if (--loadcnt == 0)
 			Lck_DestroyClass(&vsc_seg);
+		break;
+	case VCL_EVENT_WARM:
+		if (warmcnt++ == 0) {
+			AZ(mempool);
+			mempool = mpl_init();
+			AN(mempool);
+		}
+		break;
+	case VCL_EVENT_COLD:
+		AN(warmcnt);
+		if (--warmcnt == 0) {
 			AN(mempool);
 			mpl_fini(&mempool);
 			AZ(mempool);
 		}
-		return (0);
+		break;
 	default:
-		return (0);
+		WRONG("Illegal event enum");
 	}
+	return (0);
 }
 
 /* Functions */