dnsdist: Speed-up of the leastOutstanding policy

diff --git a/pdns/dnsdistdist/dnsdist-lbpolicies.cc b/pdns/dnsdistdist/dnsdist-lbpolicies.cc
index 095ad9620f62763ea70395310a0f2bc656575a43..a3175e4e59f83756b7e0799246f347433796ccb3 100644 (file)
--- a/pdns/dnsdistdist/dnsdist-lbpolicies.cc
+++ b/pdns/dnsdistdist/dnsdist-lbpolicies.cc
@@ -35,19 +35,24 @@ shared_ptr<DownstreamState> leastOutstanding(const ServerPolicy::NumberedServerV
     return servers[0].second;
   }
 
-  vector<pair<tuple<int,int,double>, shared_ptr<DownstreamState>>> poss;
+  vector<pair<tuple<int,int,double>, size_t>> poss;
   /* so you might wonder, why do we go through this trouble? The data on which we sort could change during the sort,
      which would suck royally and could even lead to crashes. So first we snapshot on what we sort, and then we sort */
   poss.reserve(servers.size());
-  for(auto& d : servers) {
+  size_t position = 0;
+  for(const auto& d : servers) {
     if(d.second->isUp()) {
-      poss.push_back({make_tuple(d.second->outstanding.load(), d.second->order, d.second->latencyUsec), d.second});
+      poss.emplace_back(make_tuple(d.second->outstanding.load(), d.second->order, d.second->latencyUsec), position);
     }
+    ++position;
   }
-  if(poss.empty())
+
+  if (poss.empty()) {
     return shared_ptr<DownstreamState>();
+  }
+
   nth_element(poss.begin(), poss.begin(), poss.end(), [](const decltype(poss)::value_type& a, const decltype(poss)::value_type& b) { return a.first < b.first; });
-  return poss.begin()->second;
+  return servers.at(poss.begin()->second).second;
 }
 
 shared_ptr<DownstreamState> firstAvailable(const ServerPolicy::NumberedServerVector& servers, const DNSQuestion* dq)
@@ -66,7 +71,7 @@ static shared_ptr<DownstreamState> valrandom(unsigned int val, const ServerPolic
   int sum = 0;
   int max = std::numeric_limits<int>::max();
 
-  for(auto& d : servers) {      // w=1, w=10 -> 1, 11
+  for(const auto& d : servers) {      // w=1, w=10 -> 1, 11
     if(d.second->isUp()) {
       // Don't overflow sum when adding high weights
       if(d.second->weight > max - sum) {
@@ -184,7 +189,6 @@ shared_ptr<DownstreamState> roundrobin(const ServerPolicy::NumberedServerVector&
     return shared_ptr<DownstreamState>();
 
   static unsigned int counter;
- 
   return (*res)[(counter++) % res->size()].second;
 }