set MAXCHANNELS to 128

src/graph/paths.cc

@@ -908,7 +908,7 @@ ncclResult_t ncclTopoComputeP2pChannels(struct ncclComm* comm) {
     comm->p2pnChannelsPerPeer = (ncclParamNChannelsPerPeer() == -2 ? nextPow2(minChannels) : ncclParamNChannelsPerPeer());
     // Doubling P2P channels per peer on single node
     if (comm->topo->nodes[GPU].count == comm->topo->nRanks && IsArchMatch(comm->topo->nodes[GPU].nodes[0].gpu.gcn, "gfx94")) comm->p2pnChannelsPerPeer *= 2;
-    comm->p2pnChannels = nextPow2(comm->p2pnChannels);
+    comm->p2pnChannels = std::min(nextPow2(comm->p2pnChannels), 4*CHANNEL_LIMIT);
   }
 
   // Init channels that weren't used so far
@@ -918,7 +918,7 @@ ncclResult_t ncclTopoComputeP2pChannels(struct ncclComm* comm) {
   // fill the whole space of nChannels. To do so we mirror the bits in the
   // nChannels space.
   for (int c=0; c<comm->p2pnChannels; c++) {
-    comm->p2pChannels[c] = mirrorBits(c, comm->p2pnChannels);
+      comm->p2pChannels[c] = mirrorBits(c, comm->p2pnChannels);
   }
   return ncclSuccess;
 }
@@ -950,4 +950,4 @@ int ncclTopoPathAllNVLink(struct ncclTopoSystem* system) {
     }
   }
   return minPath >= PATH_PIX ? 0 : 1;
-}
+}