| .TH swapin 8 "2019-07-05" "USER COMMANDS" |
| .SH NAME |
| swapin \- Count swapins by process. Uses BCC/eBPF. |
| .SH SYNOPSIS |
| .B swapin |
| .TP |
| .BR \-h ", " \-\-help\fR |
| show this help message and exit |
| .TP |
| .BR \-T ", " \-\-notime\fR |
| do not show the timestamp (HH:MM:SS) |
| .SH 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. |
| .SH REQUIREMENTS |
| CONFIG_BPF and BCC. |
| .SH EXAMPLES |
| .TP |
| Count swapins by process, showing per-second summaries. |
| # |
| .B swapin |
| .SH FIELDS |
| .TP |
| 1st |
| The process name. |
| .TP |
| 2nd |
| The process ID. |
| .TP |
| 3rd |
| The count of swapins during that interval. |
| .SH 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. |
| .SH SOURCE |
| This originated as a bpftrace tool from the book "BPF Performance Tools", |
| published by Addison Wesley (2019): |
| .IP |
| http://www.brendangregg.com/bpf-performance-tools-book.html |
| .PP |
| See the book for more documentation on this tool. |
| .PP |
| This version is in the BCC repository: |
| .IP |
| https://github.com/iovisor/bcc |
| .PP |
| Also look in the bcc distribution for a companion _examples.txt file |
| containing example usage, output, and commentary for this tool. |
| .SH OS |
| Linux |
| .SH STABILITY |
| Unstable - in development. |
| .SH AUTHOR |
| Brendan Gregg |
| .SH SEE ALSO |
| swapon(8) |
