NAME¶

bitesize.bt - Show disk I/O size as a histogram. Uses bpftrace/eBPF.

SYNOPSIS¶

bitesize.bt

DESCRIPTION¶

This can be used to characterize the distribution of block device (disk) I/O sizes. To study block device I/O in more detail, see biosnoop.bt(8).

This uses the tracepoint:block:block_rq_issue tracepoint, and is a simple example of bpftrace.

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

REQUIREMENTS¶

CONFIG_BPF and bpftrace.

EXAMPLES¶

Trace block I/O and summarize as a histogram by process:

# bitesize.bt

FIELDS¶

0th

A process name (shown in "@[...]") is printed before each I/O histogram.

1st, 2nd

This is a range of I/O sizes, in Kbytes (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¶

Since block device I/O usually has a relatively low frequency (< 10,000/s), the overhead for this tool is expected to be low or 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.

https://github.com/iovisor/bcc

OS¶

Linux

STABILITY¶

Unstable - in development.

AUTHOR¶

Brendan Gregg

SEE ALSO¶

biosnoop.bt(8)