biosnoop.bt(8) System Manager's Manual biosnoop.bt(8)
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*() ker-
nel 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 applica-
tion process, but I/O may be initiated from kernel threads only.
PID Issuing process ID. This often identifies the issuing applica-
tion 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)
USER COMMANDS 2018-09-11 biosnoop.bt(8)
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