Keep track of the highest client id the stratifier has seen to avoid needing to iterate over all disconnects to see if it exists

src/stratifier.c

@@ -320,6 +320,7 @@ struct stratifier_data {
 	ckmsgq_t *stxnq;	// Transaction requests
 
 	int64_t user_instance_id;
+	int64_t highest_client_id; /* Highest known client id */
 
 	/* Stratum_instances hashlist is stored by id, whereas disconnected_instances
 	 * is sorted by enonce1_64. */
@@ -1173,17 +1174,24 @@ static stratum_instance_t *ref_instance_by_id(sdata_t *sdata, const int64_t id)
 static bool __dropped_instance(sdata_t *sdata, const int64_t id)
 {
 	stratum_instance_t *client, *tmp;
-	bool ret = true;
+	bool ret = false;
 
+	/* Avoid iterating over all the instances if we haven't seen an id this high
+	 * before as the value only ever increases */
+	if (id > sdata->highest_client_id)
+		goto out;
 	HASH_ITER(hh, sdata->disconnected_instances, client, tmp) {
-		if (unlikely(client->id == id))
+		if (unlikely(client->id == id)) {
+			ret = true;
 			goto out;
+		}
 	}
 	DL_FOREACH(sdata->dead_instances, client) {
-		if (unlikely(client->id == id))
+		if (unlikely(client->id == id)) {
+			ret = true;
 			goto out;
+		}
 	}
-	ret = false;
 out:
 	return ret;
 }
@@ -1264,6 +1272,8 @@ static stratum_instance_t *__stratum_add_instance(ckpool_t *ckp, const int64_t i
 
 	sdata->stratum_generated++;
 	client->id = id;
+	if (id > sdata->highest_client_id)
+		sdata->highest_client_id = id;
 	client->server = server;
 	client->diff = client->old_diff = ckp->startdiff;
 	client->ckp = ckp;