NAME

       biosnoop.bt - Block I/O tracing tool, showing per I/O latency. Uses bpftrace/eBPF.

SYNOPSIS

       biosnoop.bt

DESCRIPTION

       This  is a basic block I/O (disk I/O) tracing tool, showing each I/O event along with the issuing process
       ID, and the I/O latency. This can be used to investigate disk I/O performance issues.

       This tool currently works by dynamic tracing of the blk_account*()  kernel  functions,  which  will  need
       updating to match any changes to these functions in future kernels versions.

       Since this uses BPF, only the root user can use this tool.

REQUIREMENTS

       CONFIG_BPF and bpftrace.

EXAMPLES

       Trace block I/O events, printing per-line summaries:
              # biosnoop.bt

FIELDS

       TIME   Time of the I/O completion, in milliseconds since program start.

       COMM   Issuing  process  name.  This  often  identifies  the  issuing application process, but I/O may be
              initiated from kernel threads only.

       PID    Issuing process ID. This often  identifies  the  issuing  application  process,  but  I/O  may  be
              initiated from kernel threads only.

       ARGS   Process name and arguments (16 word maximum).

OVERHEAD

       Since block device I/O usually has a relatively low frequency (< 10,000/s), the overhead for this tool is
       expected to be negligible. For high IOPS storage systems, test and quantify before use.

SOURCE

       This is from bpftrace.

              https://github.com/iovisor/bpftrace

       Also  look  in  the  bpftrace  distribution  for a companion _examples.txt file containing example usage,
       output, and commentary for this tool.

       This is a bpftrace version of the bcc tool of the same name. The bcc tool provides more fields.

              https://github.com/iovisor/bcc

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       opensnoop.bt(8)

USER COMMANDS                                      2018-09-11                                     biosnoop.bt(8)