2017-12-17
The Advent of Void: Day 17: dstat
There are many ways to see what’s going on your system, such as top(1), htop(1), atop(1). However, these tools only show the current state of the system, and it’s not so easy to see how the data changes.
dstat(1) works differently: it prints a line every second with some system stats you can configure. By default, it shows CPU usage, disk I/O, network traffic, paging, and context switches:
% dstat
You did not select any stats, using -cdngy by default.
--total-cpu-usage-- -dsk/total- -net/total- ---paging-- ---system--
usr sys idl wai stl| read writ| recv send| in out | int csw
45 9 45 1 0| 284k 181k| 0 0 | 18k 36k| 754 2181
28 6 65 1 0| 0 0 |4698k 222k| 0 0 |4123 17k
34 8 58 0 0| 0 0 |4730k 220k| 0 0 |5253 20k
29 8 62 1 0|4096B 1080k|4640k 215k| 0 0 |4383 18k
37 7 38 17 0| 0 15M|4844k 219k| 0 0 |5532 21k
31 8 30 32 0| 336k 6840k|5153k 232k| 0 0 |4383 17k
...
For Void development, I like to run this configuration; showing per-core CPU usage, memory usage, process spawn rate and I/O.
% dstat --cpu-use -mpr
---------per-cpu-usage--------- ------memory-usage----- ---procs--- --io/total-
0 1 2 3 4 5 6 7 | used free buff cach|run blk new| read writ
4 2 1 1 1 1 1 1| 550M 2510M 2823M 1315M| 0 0 4.4|6.42 0.93
1 0 0 0 0 1 0 0| 550M 2510M 2823M 1315M| 0 0 1.0| 0 0
2 2 1 1 0 0 0 1| 551M 2508M 2823M 1315M| 0 0 20| 0 0
1 0 0 0 0 0 0 0| 551M 2508M 2823M 1315M| 0 0 0| 0 0
0 0 0 0 0 0 0 0| 551M 2509M 2823M 1315M| 0 0 0| 0 0
2 0 0 0 0 1 0 0| 551M 2509M 2823M 1315M| 0 0 0| 0 0
This allows us to easily detect if builds are not optimally parallelized,
or whether we run into memory limits.
And process spawn rate detects if a ./configure script runs. ;)
dstat includes a huge list of probes it can display, just to list a few: battery usage, free disk, MySQL/InnoDB stats, qmail queue size, NFS traffic, NTP stats, WiFi measurements, ZFS information.
It’s a very versatile tool, and because it works via the console, you can also easily run it over SSH.