NAME

       xfsdist.bt - Summarize XFS operation latency. Uses bpftrace/eBPF.

SYNOPSIS

       xfsdist.bt

DESCRIPTION

       This tool summarizes time (latency) spent in common XFS file operations: reads, writes, opens, and syncs,
       and  presents  it  as  a  power-of-2  histogram. It uses an in-kernel eBPF map to store the histogram for
       efficiency.

       Since this works by tracing the xfs_file_operations interface functions, it will need updating  to  match
       any changes to these functions.

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

REQUIREMENTS

       CONFIG_BPF and bpftrace.

EXAMPLES

       Trace XFS operation time, and print a summary on Ctrl-C:
              # xfsdist.bt

FIELDS

       0th    The operation name (shown in "@[...]") is printed before each I/O histogram.

       1st, 2nd
              This is a range of latency, in microseconds (shown in "[...)" set notation).

       3rd    A column showing the count of operations in this range.

       4th    This is an ASCII histogram representing the count column.

OVERHEAD

       This  adds low-overhead instrumentation to these XFS operations, including reads and writes from the file
       system cache. Such reads and writes can be very frequent (depending on  the  workload;  eg,  1M/sec),  at
       which point the overhead of this tool may become noticeable.  Measure and quantify before use.

SOURCE

       This is from bpftrace.

              https://github.com/bpftrace/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 may provide  more  options  and
       customizations.

              https://github.com/iovisor/bcc

OS

       Linux

STABILITY

       Unstable - in development.

AUTHOR

       Brendan Gregg

SEE ALSO

       biolatency.bt(8)

USER COMMANDS                                      2018-09-08                                      xfsdist.bt(8)