1Demonstrations of disksnoop.py, the Linux eBPF/bcc version. 2 3 4This traces block I/O, a prints a line to summarize each I/O completed: 5 6# ./disksnoop.py 7TIME(s) T BYTES LAT(ms) 816458043.435457 W 4096 2.73 916458043.435981 W 4096 3.24 1016458043.436012 W 4096 3.13 1116458043.437326 W 4096 4.44 1216458044.126545 R 4096 42.82 1316458044.129872 R 4096 3.24 1416458044.130705 R 4096 0.73 1516458044.142813 R 4096 12.01 1616458044.147302 R 4096 4.33 1716458044.148117 R 4096 0.71 1816458044.148950 R 4096 0.70 1916458044.164332 R 4096 15.29 2016458044.168003 R 4096 3.58 2116458044.171676 R 4096 3.59 2216458044.172453 R 4096 0.72 2316458044.173213 R 4096 0.71 2416458044.173989 R 4096 0.72 2516458044.174739 R 4096 0.70 2616458044.190334 R 4096 15.52 2716458044.196608 R 4096 6.17 2816458044.203091 R 4096 6.35 29 30The output includes a basic timestamp (in seconds), the type of I/O (W == write, 31R == read, M == metadata), the size of the I/O in bytes, and the latency (or 32duration) of the I/O in milliseconds. 33 34The latency is measured from I/O request to the device, to the device 35completion. This excludes latency spent queued in the OS. 36 37Most of the I/O in this example were 0.7 and 4 milliseconds in duration. There 38was an outlier of 42.82 milliseconds, a read which followed many writes (the 39high latency may have been caused by the writes still being serviced on the 40storage device). 41