atop quick start: an introduction to atop snapshotting
Nov 12, 2014 · 4 minute readatop is a server diagnostic tool to take snapshots of the server’s activity at specified intervals, so it’s useful for debugging intermitttent issues without watching the server constantly.
atop is available to install from the repos with a yum install atop or apt-get install atop depending if you’re on a RedHat or Debian-based server. By default atop will take snapshots every 10 minutes.
Omnce it’s been left running, you can view its snapshots by running atop -r /var/log/atop/atop_<date> - you can see the dates that are logged by listing the /var/log/atop directory.
Two key commands to use are b and t. Pressing b will prompt for a time in the format hh:mm. Enter a time and it’ll jump to the nearest snapshot. From there t and T (shift-t) will jump you forwards and backwards through the logs respectively
This is an example of atop’s output:
ATOP - ip-10-0-1-22 2014/11/11 00:30:02 ----------- 10m0s elapsed
PRC | sys 5.11s | user 10.94s | | | #proc 104 | #trun 1 | | #tslpi 149 | #tslpu 0 | | #zombie 0 | clones 37 | | | #exit 46 |
CPU | sys 1% | user 2% | | irq 0% | | idle 197% | | wait 0% | | | steal 0% | guest 0% | curf 2.50GHz | | curscal ?% |
cpu | sys 1% | user 1% | | irq 0% | | idle 98% | | cpu001 w 0% | | | steal 0% | guest 0% | curf 2.50GHz | | curscal ?% |
cpu | sys 0% | user 0% | | irq 0% | | idle 99% | | cpu000 w 0% | | | steal 0% | guest 0% | curf 2.50GHz | | curscal ?% |
CPL | avg1 0.14 | | avg5 0.09 | | avg15 0.07 | | | csw 261923 | | intr 279857 | | | | numcpu 2 | |
MEM | tot 7.3G | free 5.8G | cache 176.1M | dirty 0.8M | buff 14.2M | slab 41.4M | slrec 20.1M | shmem 36.9M | shrss 0.0M | shswp 0.0M | | vmbal 0.0M | | hptot 0.0M | hpuse 0.0M |
SWP | tot 0.0M | free 0.0M | | | | | | | | | | | vmcom 2.1G | vmlim 3.6G | |
NET | transport | tcpi 69012 | tcpo 74002 | | udpi 93 | udpo 97 | tcpao 72 | tcppo 330 | | tcprs 250 | tcpie 0 | tcpor 24 | udpnp 0 | | udpie 0 |
NET | network | ipi 69105 | | ipo 74025 | ipfrw 0 | | deliv 69105 | | | | | | icmpi 0 | icmpo 0 | |
NET | eth0 ---- | pcki 68732 | | pcko 73654 | si 342 Kbps | so 464 Kbps | | coll 0 | mlti 0 | | erri 0 | erro 0 | drpi 0 | | drpo 0 |
NET | lo ---- | pcki 396 | | pcko 396 | si 17 Kbps | so 17 Kbps | | coll 0 | mlti 0 | | erri 0 | erro 0 | drpi 0 | | drpo 0 |
Window resized to 238x71...
PID TID RUID EUID THR SYSCPU USRCPU VGROW RGROW RDDSK WRDSK ST EXC S CPUNR CPU CMD 1/3
1335 - root root 7 2.51s 2.97s 0K 0K 0K 0K -- - S 1 1% glusterfs
17247 - apache apache 1 0.40s 4.34s 46644K 66352K 3340K 3292K -- - S 1 1% httpd
17274 - apache apache 1 0.36s 1.13s 35236K 54628K 1188K 2304K -- - S 0 0% httpd
17267 - apache apache 1 0.24s 0.94s 55204K 83040K 2348K 2760K -- - S 1 0% httpd
17310 - apache apache 1 0.26s 0.49s 961.9M 83508K 548K 12K N- - S 1 0% httpd
16708 - varnish varnish 19 0.28s 0.08s 4992K 5188K 32588K 448K -- - S 0 0% varnishd
17248 - apache apache 1 0.11s 0.17s 7128K 24120K 364K 1788K -- - S 1 0% httpd
17187 - root root 1 0.18s 0.04s 140K 140K 0K 24K -- - R 1 0% atop
1418 - root root 7 0.11s 0.10s 0K 0K 0K 0K -- - S 1 0% glusterfs
17309 - apache apache 1 0.06s 0.10s 922.2M 25716K 820K 8K N- - S 0 0% httpd
1460 - root root 7 0.07s 0.08s 0K 0K 0K 0K -- - S 1 0% glusterfs