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)