crank up blockstore max readers to 16K, reduce retry delays to 10us

chain/store/splitstore/lmdb_util.go

@@ -13,7 +13,7 @@ func withMaxReadersRetry(f func() error) error {
 retry:
 	err := f()
 	if err != nil && lmdb.IsErrno(err, lmdb.ReadersFull) {
-		dt := time.Microsecond + time.Duration(rand.Intn(int(time.Millisecond)))
+		dt := time.Microsecond + time.Duration(rand.Intn(int(10*time.Microsecond)))
 		log.Debugf("MDB_READERS_FULL; retrying operation in %s", dt)
 		time.Sleep(dt)
 		goto retry

chain/store/splitstore/splitstore.go

@@ -65,7 +65,8 @@ func NewSplitStore(path string, ds dstore.Datastore, cold bstore.Blockstore) (*S
 		InitialMmapSize:      4 << 30, // 4GiB.
 		MmapGrowthStepFactor: 1.25,    // scale slower than the default of 1.5
 		MmapGrowthStepMax:    4 << 30, // 4GiB
-		RetryDelay:           time.Millisecond,
+		RetryDelay:           10 * time.Microsecond,
+		MaxReaders:           16384,
 	})
 	if err != nil {
 		return nil, err