Manual: biostacks.bt

biostacks.bt(8)					   System Manager's Manual				     biostacks.bt(8)

NAME
       biostacks - Show disk I/O latency with initialization stacks. Uses bpftrace/eBPF.

SYNOPSIS
       biostacks

DESCRIPTION
       This  tool  shows disk I/O latency histograms for each block I/O initialization path. This can help reveal the reason
       for different latencies, as some may be created by log flushing, others by application reads, etc.

       This works by attaching to block_io_start and block_rq_issue tracepoints.

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

REQUIREMENTS
       CONFIG_BPF and bpftrace.

EXAMPLES
       Trace disk I/O latency with initialization stacks:
	      # biostacks.bt

FIELDS
       0th    An initialization kernel stack trace (shown in "@[...]") is printed before each I/O histogram.

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

       3rd    A column showing the count of I/O in this range.

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

OVERHEAD
       The rate of biostacks should be low (bounded by device IOPS), such that the overhead of this tool is expected  to  be
       negligible.

SOURCE
       This tool originated from the book "BPF Performance Tools", published by Addison Wesley (2019):

	      http://www.brendangregg.com/bpf-performance-tools-book.html

       See the book for more documentation on this tool.

       This version is in the bpftrace repository:

	      https://github.com/bpftrace/bpftrace

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

OS
       Linux

STABILITY
       Unstable - in development.

AUTHOR
       Brendan Gregg

SEE ALSO
       biosnoop.bt(8)

USER COMMANDS						 2019-07-12					     biostacks.bt(8)