Jeff, thanks for your reply. unfortunately, the website is in maintenance. The reason I monitored the system calls of HDFS is to try to find out what activities cause so much system CPU time. Other than writing to the disk and sending and receiving packets, I cannot think of anything else that can consume large system CPU time. Unfortunately, I wrote a simple program outputting data (to the disk and the network) at the same rate, it can only consume far less system CPU time.
Da On 1/30/11 5:25 PM, Jeff Hammerbacher wrote: > Hey Da, > > You may have observed https://issues.apache.org/jira/browse/HDFS-1601. > > Regards, > Jeff > > On Fri, Jan 28, 2011 at 7:08 PM, Da Zheng <[email protected]> wrote: > >> Hello, >> >> I monitored system calls of HDFS with systemtap and found HDFS actually >> sends >> many 1-byte data to the network. I could also see many 8-byte and 64-byte >> data >> written to the OS though I don't know whether they are written to the disk >> or >> sent to the network. I did see many 8-byte data sent to the network. The >> number >> of these data is several times more than 64KB data packet sent by HDFS. >> >> Could anyone tell me why HDFS sends so many small packets? heartbeat >> messages? >> RPCs? It doesn't seem to me these messages can be just 1 byte. >> >> Thanks, >> Da >> >
