Improve addrman Select() performance when buckets are nearly empty

src/addrman.cpp

@@ -341,8 +341,10 @@ CAddrInfo CAddrMan::Select_()
         while (1) {
             int nKBucket = GetRandInt(ADDRMAN_TRIED_BUCKET_COUNT);
             int nKBucketPos = GetRandInt(ADDRMAN_BUCKET_SIZE);
-            if (vvTried[nKBucket][nKBucketPos] == -1)
+            while (vvTried[nKBucket][nKBucketPos] == -1) {
-                continue;
+                nKBucket = (nKBucket + insecure_rand()) % ADDRMAN_TRIED_BUCKET_COUNT;
+                nKBucketPos = (nKBucketPos + insecure_rand()) % ADDRMAN_BUCKET_SIZE;
+            }
             int nId = vvTried[nKBucket][nKBucketPos];
             assert(mapInfo.count(nId) == 1);
             CAddrInfo& info = mapInfo[nId];
@@ -356,8 +358,10 @@ CAddrInfo CAddrMan::Select_()
         while (1) {
             int nUBucket = GetRandInt(ADDRMAN_NEW_BUCKET_COUNT);
             int nUBucketPos = GetRandInt(ADDRMAN_BUCKET_SIZE);
-            if (vvNew[nUBucket][nUBucketPos] == -1)
+            while (vvNew[nUBucket][nUBucketPos] == -1) {
-                continue;
+                nUBucket = (nUBucket + insecure_rand()) % ADDRMAN_NEW_BUCKET_COUNT;
+                nUBucketPos = (nUBucketPos + insecure_rand()) % ADDRMAN_BUCKET_SIZE;
+            }
             int nId = vvNew[nUBucket][nUBucketPos];
             assert(mapInfo.count(nId) == 1);
             CAddrInfo& info = mapInfo[nId];