NAME

biotop - Block device (disk) I/O by process top.

SYNOPSIS

biotop [-h] [-C] [-r MAXROWS] [interval] [count]

DESCRIPTION

This is top for disks.

This traces block device I/O (disk I/O), and prints a per-process summary every interval (by default, 1 second). The summary is sorted on the top disk consumers by throughput (Kbytes). The PID and process name shown are measured from when the I/O was first created, which usually identifies the responsible process.

For efficiency, this uses in-kernel eBPF maps to cache process details (PID and comm) by I/O request, as well as a starting timestamp for calculating I/O latency, and the final summary.

This works by tracing various kernel blk_*() functions using dynamic tracing, and 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 bcc.

OPTIONS

-C: Don't clear the screen.
-r MAXROWS: Maximum number of rows to print. Default is 20.
interval: Interval between updates, seconds.
count: Number of interval summaries.

EXAMPLES

Summarize block device I/O by process, 1 second screen refresh:: # biotop
Don't clear the screen:: # biotop -C
5 second summaries, 10 times only:: # biotop 5 10

FIELDS

loadavg:: The contents of /proc/loadavg
PID: Cached process ID, if present. This usually (but isn't guaranteed) to identify the responsible process for the I/O.
COMM: Cached process name, if present. This usually (but isn't guaranteed) to identify the responsible process for the I/O.
D: Direction: R == read, W == write. This is a simplification.
MAJ: Major device number.
MIN: Minor device number.
DISK: Disk device name.
I/O: Number of I/O during the interval.
Kbytes: Total Kbytes for these I/O, during the interval.
AVGms: Average time for the I/O (latency) from the issue to the device, to its completion, in milliseconds.

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 bcc.

: https://github.com/iovisor/bcc

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

OS

Linux

STABILITY

Unstable - in development.

AUTHOR

Brendan Gregg

INSPIRATION

top(1) by William LeFebvre