public static void checkShortCircuitReadBufferSize(final Configuration conf) {
    final int defaultSize = HConstants.DEFAULT_BLOCKSIZE * 2;
    final int notSet = -1;
    // DFSConfigKeys.DFS_CLIENT_READ_SHORTCIRCUIT_BUFFER_SIZE_KEY is only defined in h2
    final String dfsKey = "dfs.client.read.shortcircuit.buffer.size";
    int size = conf.getInt(dfsKey, notSet);
    // If a size is set, return -- we will use it.
    if (size != notSet) return;
    // But short circuit buffer size is normally not set. Put in place the hbase wanted size.
    int hbaseSize = conf.getInt("hbase." + dfsKey, defaultSize);
    conf.setIfUnset(dfsKey, Integer.toString(hbaseSize));
  }
Check if short circuit read buffer size is set and if not, set it to hbase value.
hbase-server/src/main/java/org/apache/hadoop/hbase/util/FSUtils.java