massively improve sync speed

src/main.cpp

@@ -2789,7 +2789,7 @@ bool ActivateBestChain(CValidationState& state, CBlock* pblock, bool fAlreadyChe
             uiInterface.NotifyBlockTip(hashNewTip);
         }
     } while (pindexMostWork != chainActive.Tip());
-    CheckBlockIndex();
+    // CheckBlockIndex();
 
     // Write changes periodically to disk, after relay.
     if (!FlushStateToDisk(state, FLUSH_STATE_PERIODIC)) {
@@ -3600,7 +3600,7 @@ bool ProcessNewBlock(CValidationState& state, CNode* pfrom, CBlock* pblock, CDis
         if (pindex && pfrom) {
             mapBlockSource[pindex->GetBlockHash ()] = pfrom->GetId ();
         }
-        CheckBlockIndex ();
+        // CheckBlockIndex ();
         if (!ret)
             return error ("%s : AcceptBlock FAILED", __func__);
     }

src/main.h

@@ -88,7 +88,7 @@ static const int MAX_SCRIPTCHECK_THREADS = 16;
 /** -par default (number of script-checking threads, 0 = auto) */
 static const int DEFAULT_SCRIPTCHECK_THREADS = 0;
 /** Number of blocks that can be requested at any given time from a single peer. */
-static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 128;
+static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 256;
 /** Timeout in seconds during which a peer must stall block download progress before being disconnected. */
 static const unsigned int BLOCK_STALLING_TIMEOUT = 2;
 /** Number of headers sent in one getheaders result. We rely on the assumption that if a peer sends