(trunk libT) #3329 "connection problems when downloading" -- apply Longinus00's fixSlowStart.diff

libtransmission/peer-mgr.c

@@ -193,6 +193,8 @@ typedef struct tr_torrent_peers
     int                        pieceCount;
 
     int                        interestedCount;
+    int                        maxPeers;
+    tr_recentHistory         * noBlocksCancelsCount;
 
     /* An arbitrary metric of how congested the downloads are.
      * Based on how many of requests are cancelled and how many are completed.
@@ -450,6 +452,7 @@ torrentDestructor( void * vt )
     tr_ptrArrayDestruct( &t->pool, (PtrArrayForeachFunc)tr_free );
     tr_ptrArrayDestruct( &t->outgoingHandshakes, NULL );
     tr_ptrArrayDestruct( &t->peers, NULL );
+    tr_historyFree( t->noBlocksCancelsCount );
 
     tr_free( t->requests );
     tr_free( t->pieces );
@@ -472,6 +475,7 @@ torrentConstructor( tr_peerMgr * manager,
     t->peers = TR_PTR_ARRAY_INIT;
     t->webseeds = TR_PTR_ARRAY_INIT;
     t->outgoingHandshakes = TR_PTR_ARRAY_INIT;
+    t->noBlocksCancelsCount = tr_historyNew( CANCEL_HISTORY_SEC, 1 );
 
     for( i = 0; i < tor->info.webseedCount; ++i )
     {
@@ -2486,36 +2490,58 @@ rechokeDownloads( Torrent * t )
             cancels += c;
         }
 
-        if( !t->interestedCount )
+        if( !t->maxPeers )
         {
             /* this is the torrent's first time to call this function...
              * start off optimistically by allowing interest in many peers */
             maxPeers = t->tor->maxConnectedPeers;
         }
-        else if( !blocks )
+        else if( !blocks && cancels )
         {
             /* we've gotten cancels but zero blocks...
              * something is seriously wrong.  throttle back sharply */
             maxPeers = t->interestedCount * 0.5;
         }
-        else
+        else if( blocks )
         {
-            const double cancelRate = cancels / (double)(cancels + blocks);
+            const double cancelRate = cancels / (double)(cancels + blocks );
+
+            /* if we're getting cancels then use interestedCount instead of
+             * maxPeers to scale faster */
                  if( cancelRate >= 0.20 ) maxPeers = t->interestedCount * 0.7;
             else if( cancelRate >= 0.10 ) maxPeers = t->interestedCount * 0.8;
             else if( cancelRate >= 0.05 ) maxPeers = t->interestedCount * 0.9;
             else if( cancelRate >= 0.01 ) maxPeers = t->interestedCount;
-            else                          maxPeers = t->interestedCount + 1;
+            else                          maxPeers = t->maxPeers + 1;
 
             /* if things are getting worse, don't add more peers */
             if( ( t->cancelRate > 0.01 ) && ( cancelRate > t->cancelRate ) )
-                maxPeers = MIN( maxPeers, t->interestedCount );
+                maxPeers = MIN( maxPeers, t->maxPeers );
 
             t->cancelRate = cancelRate;
 
             tordbg( t, "cancel rate is %.3f -- changing the "
                        "number of peers we're interested in from %d to %d",
-                       cancelRate, t->interestedCount, maxPeers );
+                       cancelRate, t->maxPeers, maxPeers );
+        }
+        else
+        {
+            const unsigned maxCount = 10; /* maximum times in this block in the past two minutes */
+            tr_historyAdd( t->noBlocksCancelsCount, now, 1 );
+            if( tr_historyGet( t->noBlocksCancelsCount, now, msec * 2 ) < maxCount )
+            {
+                /* no blocks and no cancels means either that the torrent
+                 * just started or peers are unresponsive/nonexistent,
+                 * either way there's nothing to do */
+                maxPeers = t->maxPeers;
+            }
+            else
+            {
+                /* we've been in here for a while so maybe the network is down or there are no
+                 * good peers. maximize the chance of connecting to a good peer
+                 * if/when they show up */
+                maxPeers = t->tor->maxConnectedPeers;
+            }
         }
     }
 
@@ -2525,6 +2551,8 @@ rechokeDownloads( Torrent * t )
     if( maxPeers > t->tor->maxConnectedPeers )
         maxPeers = t->tor->maxConnectedPeers;
 
+    t->maxPeers = maxPeers;
+
     /* separate the peers into "good" (ones with a low cancel-to-block ratio),
      * untested peers, and "bad" (ones with a high cancel-to-block ratio).
      * That's the order in which we'll choose who to show interest in */