答复: why my test result on dfs short circuit read is slower?

Probably readahead played a key role on the first scenario(scan only job) ? the default LONG_READ_THRESHOLD_BYTES(BlockSender.java) is 256k in current codebase, and ReadaheadPool takes effect on normal read path. Regards, Liang 发件人: Liu, Raymond [raymon

答复: why my test result on dfs short circuit read is slower?

I'm not very clear about your senario, just a kindly reminder: "If security is on, the feature can be used only for user that has kerberos credentials at the client, therefore map reduce tasks cannot benefit from it in general", see HDFS-2246's release note for more info If you didn't enable se

答复: why my test result on dfs short circuit read is slower?

Hi Raymond, did you enable security feature in your cluster? there'll be no obvious benefit be found if so. Regards, Liang ___ 发件人: Liu, Raymond [raymond@intel.com] 发送时间: 2013年2月16日 11:10 收件人: user@hadoop.apache.org 主题: why my test result on dfs short cir