NAME¶

swapin.bt - Count swapins by process. Uses bpftrace/eBPF.

SYNOPSIS¶

swapin

DESCRIPTION¶

This tool counts swapins by process, to show which process is affected by swapping (if swap devices are in use). This can explain a significant source of application latency, if it has began swapping due to memory pressure on the system.

This works by tracing the swap_readpage() kernel function using dynamic instrumentation. This tool may need maintenance to keep working if that function changes in later kernels.

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

REQUIREMENTS¶

CONFIG_BPF and bpftrace.

EXAMPLES¶

Count swapins by process, showing per-second summaries.

# swapin.bt

FIELDS¶

1st

The process name.

2nd

The process ID.

3rd

The count of swapins during that interval.

OVERHEAD¶

The rate of swapins should be low (bounded by swapin 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/iovisor/bpftrace

Also look in the bpftrace 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

SEE ALSO¶

swapon(8)