Explanation of everything you can see in htop/top on Linux (2019)

I've relatively recently migrated over to using btop[0], and it's the kind of modern interface, useful and informative, that I needed.

As others mention it - it seems to shows the Watts used as well :) (and network, and GPU, and disks,....)

[0]: https://github.com/aristocratos/btop

2 Settings I change on every htop which makes a HUGE difference.

1. I disable user threads. Those mostly just clutter up the htop view while providing no useful information.

2. I enable the process tree view. Very frequently, where a process comes from is much more important than other information. It also lets you see and track things like a compiler process which is eating through a bunch of files.

IMO, both these things should be the default behavior of htop.

I appreciate the note on virtual memory not being reliable. This is what Windows task manager reports by default and it's terrible. Resident size is the most reliable metric. Anything else can be wrongfully inflated by things like harmless memory mapped files that won't actually hurt anything. eg. memory map 2GB of logfiles, it'll only be paged in if reading that portion of the logfile so isn't really using memory but users look at the processes and claim "OMG why does this app use so much memory". It doesn't. It uses very little. You're reading the memory usage wrong. Chrome actually had this problem for a while and they moved away from using memory mapped files. Not because memory mapped files are a bad thing but because users will read the memory usage and go crazy over what they see even though it's not really using that much actual physical memory.

There's actually guides out there on the web that tell people judge usage by virtual memory allocated too :(. At least this article gets it right :).

When I read stuff like this, I come to the realization that even after daily driving Linux for 20+ years I still barely utilize its full potential. Great article.

Anyone else feel as if HN is healing? I hope this isn't the walking-ghost era of HN.

For top if you use the > character it will sort by memory usage. I use that sometimes to figure out why my host is becoming laggy. Also you'll see swapd is taking up CPU.

For the ones that don't know "nmon", have a look at it as well! (press "h" to see the list of available monitors - press it again to make it go away, press "q" to quit)

https://nmon.sourceforge.io/pmwiki.php

Especially disk throughput and I/O (keys "d" & "D") can be very useful.

I've had this bookmarked since 2016, and have referred to it many times over the years.

A different usage paradigm from *top that I have come to like better is to do differential ps-like reports and system-wide (like vmstat) reports which leaves everything in your terminal scrollback buffer as in: https://github.com/c-blake/procs { written in the uncommonly efficient, expressive Nim programming language }.

This is really good!

I use htop often but pretty much only use it to find pid or cpu-culprits, and never really understood the rest.

Very interesting topic,Cool.

   /*
    * kernel/sched/loadavg.c
    *
    * This file contains the magic bits required to compute the global loadavg
    * figure. Its a silly number but people think its important. We go through
    * great pains to make it work on big machines and tickless kernels.
    */

so is it just silly numbers or important ?

s/htop/btop/

You'll be glad you did.

A bit silly that you can see a load average but not the amount of Watts used by your system.