hash: Log the VXID of requests being rushed

This is very useful to manually verify the rush_exponent behavior.

Author: dridi

bin/varnishd/cache/cache_hash.c

@@ -715,6 +715,7 @@ hsh_rush1(const struct worker *wrk, struct objcore *oc, struct rush *r)
 {
 	struct objhead *oh;
 	struct req *req;
+	unsigned xid;
 	int max, i;
 
 	CHECK_OBJ_NOTNULL(wrk, WORKER_MAGIC);
@@ -737,6 +738,13 @@ hsh_rush1(const struct worker *wrk, struct objcore *oc, struct rush *r)
 		req = VTAILQ_FIRST(&oh->waitinglist);
 		if (req == NULL)
 			break;
+
+		if (DO_DEBUG(DBG_WAITINGLIST)) {
+			xid = VXID(req->vsl->wid);
+			VSLb(wrk->vsl, SLT_Debug,
+			    "waiting list rush for req %u", xid);
+		}
+
 		CHECK_OBJ_NOTNULL(req, REQ_MAGIC);
 		wrk->stats->busy_wakeup++;
 		AZ(req->wrk);