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command-line
ram
memory-usage
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🔍 See Original Answer on Ask Ubuntu ⧉ 🔗
URL:
https://askubuntu.com/q/1188025
Title:
How to test oom-killer from command line
ID:
/2019/11/11/How-to-test-oom-killer-from-command-line
Created:
November 11, 2019
Edited: November 12, 2019
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September 15, 2024
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Revised answer
My initial answer took 1/2 hour to execute and has been dropped in this revision:
ls -d /*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*/*
I’ll accept someone else’s answer as a faster way of invoking oom-killer from the command line. As a revised answer I’ll explain how to get relevant oom-killer details from journalctl and what they mean.
This more efficient answer by mjoao to use up RAM:
logger --tag="kernel" "Start for oom-killer"; a=""; for b in {0..99999999}; do a=$b$a$a$a$a$a$a; done
The logger command was prepended to give a timestamp in journalctl for when the RAM eating process starts.
After oom-killer is finished, open a new terminal and type oomlog (script contents later on):
$ oomlog
Nov 12 12:29:23 alien kernel[19202]: Start for oom-killer
Nov 12 12:30:02 alien kernel: 31981 total pagecache pages
Nov 12 12:30:02 alien kernel: 11627 pages in swap cache
Nov 12 12:30:02 alien kernel: Swap cache stats: add 10739122, delete 10727632, find 8444277/9983565
Nov 12 12:30:02 alien kernel: Free swap = 0kB
Nov 12 12:30:02 alien kernel: Total swap = 8252412kB
Nov 12 12:30:02 alien kernel: 2062044 pages RAM
Nov 12 12:30:02 alien kernel: 0 pages HighMem/MovableOnly
Nov 12 12:30:02 alien kernel: 56052 pages reserved
Nov 12 12:30:02 alien kernel: 0 pages cma reserved
Nov 12 12:30:02 alien kernel: 0 pages hwpoisoned
Nov 12 12:30:02 alien kernel: [ pid ] uid tgid total_vm rss nr_ptes nr_pmds swapents oom_score_adj name
Nov 12 12:30:02 alien kernel: [ 4358] 1000 4358 2853387 1773446 5578 13 1074744 0 bash
Nov 12 12:30:02 alien kernel: Out of memory: Kill process 4358 (bash) score 701 or sacrifice child
Nov 12 12:30:02 alien kernel: Killed process 4358 (bash) total-vm:11413548kB, anon-rss:7093784kB, file-rss:0kB, shmem-rss:0kB
Nov 12 12:30:03 alien kernel: oom_reaper: reaped process 4358 (bash), now anon-rss:0kB, file-rss:0kB, shmem-rss:0kB
The better answer takes 30 seconds to use up RAM which is not too fast (like tail /dev/zero) and not too slow (like my original answer).
The oomlog script condenses many pages of journalctl output into 16 lines.
The oom-killer [ pid ] fields are explained here:
- pid The process ID.
- uid User ID.
- tgid Thread group ID.
- total_vm Virtual memory use (in 4 kB pages)
- rss Resident memory use (in 4 kB pages)
- nr_ptes Page table entries
- swapents Swap entries
- oom_score_adj Usually 0; a lower number indicates the process will be less likely to die when the OOM killer is invoked.
oomlog bash script
#!/bin/bash
# NAME: oomlog
# PATH: $HOME/askubuntu/
# DESC: For: https://askubuntu.com/questions/1188024/how-to-test-oom-killer-from-command-line
# DATE: November 12, 2019.
# PARM: Parameter 1 can be journalctl boot sequence, eg -b-2 for two boots ago.
# Defaults to -b-0 (current boot).
BootNo="-b-0"
[[ $1 != "" ]] && BootNo="$1"
# Get time stamp if recorded with `logger` command:
journalctl "$BootNo" | grep 'Start for oom-killer' | tail -n1
# Print headings for last oom-killer
journalctl "$BootNo" | grep '\[ pid ]' -B10 | tail -n11
# Get lat oom_reaper entry's PID
PID=$(journalctl "$BootNo" | grep oom_reaper | tail -n1 | cut -d' ' -f9)
# Print pid information
journalctl "$BootNo" | grep "$PID"']' | tail -n1
# Print summary infomation
journalctl "$BootNo" | grep oom_reaper -B2 | tail -n3