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

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.

yomismoaqui• 18 days ago

I prefer using the more memory friendly M (uppercase) for memory and P (uppercase) for CPU

amelius• 18 days ago

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

roryirvine• 18 days ago

powertop to the rescue!

https://github.com/fenrus75/powertop

cogman10• 18 days ago

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.

zekrioca• 18 days ago

I like the process tree view, but it stops the dynamic updates and reordering of process list.

imrehg• 18 days ago

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

MomsAVoxell5• 18 days ago

Yup, btop zealot here, it even replaced iStatMenu on my brand new MacBook ..

NetOpWibby• 18 days ago

Oh wow, now I gotta check it out.

zackify• 18 days ago

Same. Btop is the best

JdeBP2• 18 days ago

Well, unless one is using FreeBSD or OpenBSD, where the btop code is still using 32-bit integers to calculate 64-bit sizes, and falling prey to unsigned integer wraparound. htop's code calculates using size_t, which ends up as a 64-bit integer on 64-bit architectures.

* https://news.ycombinator.com/item?id=48778757 (https://crocidb.com/post/freebsd-ate-my-ram/)

* https://github.com/aristocratos/btop/pull/1728

hinkley2• 18 days ago

I still occasionally use alpine as a base image for containers and it looks like both doesn’t do musl so that’s out.

bilegeek• 18 days ago

I like btop, but there are downsides:

1.) No zram/zswap statistics. (Though htop only supports zram also.)

2.) No ZFS statistics breakdown.

3.) Doesn't support Arc GPU yet.

4.) I can't disable the disk fill bars, which makes the I/O rate graphs extremely squished unless the console window is very large.

reaperducer• 18 days ago

5.) Requires an 80x24 window. Not ideal for monitoring several machines at once.

htop scales all the way down to 40x8 on my TRS-80.

internet101010• 18 days ago

Long time user of btop. Only thing it is missing is a ports column next to the others. Also I think the cpu/gpu graph graph is way oversized and would like more space occupied by the open file table in general.

MomsAVoxell5• 18 days ago

s/htop/btop/

You'll be glad you did.

allarm3• 18 days ago

What's so good about btop? I personally can't stand its interface, I don't need bells and whistles in my terminal.

MomsAVoxell5• 18 days ago

It’s something I put in a very small terminal, hitting the 1,2,3,4,5 key until I get the view I need, just right, and there it sits telling me all during my busy compiles and things, just how max’ing my system is.

It’s very informative, well designed for a TUI, and shows me everything I need to see without requiring futzing around with the menu bar, or dealing with registration nagging, or notification popups, or any of the other mundane things the non-terminal performance monitors seem to think is necessary to stain my eyeballs…

WD-42• 18 days ago

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.

love0972• 18 days ago

Very interesting topic,Cool.

AnotherGoodName• 18 days ago

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 :).

jltsiren• 18 days ago

If you use memory-mapped files, cached pages count towards the resident set size of your process. If you use ordinary file I/O, they don't. That behavior has amusing consequences in HPC clusters that monitor the memory usage of each job and kill them if they use more memory than they requested.

sedatk• 18 days ago

This is what Windows task manager reports

Just to clarify, Windows Task Manager uses Private Working Set by default for process memory usage which does NOT include shared pages with other processes such as libraries or memory mapped files (hence the name “private”). It only shows the memory that maps to privately allocated physical memory per process. It’s probably closer to Resident Set on Unix.

You probably meant the memory usage in performance tab but I wanted to clarify in case people mistake it for all memory usage fields.

d3Xt3r• 18 days ago

Resident size is the most reliable metric

Actually, Proportional Set Size is more accurate than RSS. See: https://en.wikipedia.org/wiki/Proportional_set_size

cb3212• 18 days ago

`procs display` (mentioned elsethread https://news.ycombinator.com/item?id=48788167 ) supports PSS via its %M format code.

One issue with that relative to RSS is permissions. Historically, all procs could see the RSS used by procs of all other users (at least if they could see the PIDs at all). So, RSS requires no special permissions, but the Linux kernel team decided PSS should not be as promiscuous for whatever reasons (I didn't do a deep dive). So, I'm always having to do (the equivalent of) `sudo pu`.

hinkley2• 18 days ago

Resident set size is not the amount of memory that the process wants, it’s how much the OS is willing to give it. So once memory pressure kicks in it stops being representative. I’ve seen this misunderstanding lead to bad decisions a few times. I even went so far to remove this value form charts because a team member was going left when he should have gone right.

zepearl• 18 days ago

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.

Zardoz84• 18 days ago

very useful tool. I install it on every machine where I have control. I appreciate the "Wide" CPU usage graph, that can handle huge core counts easily

shellwizard• 18 days ago

I know it from some AIX machines that we have at job, also topas comes to mind

cb3212• 18 days ago

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 }.

Maksadbek• 18 days ago

   /*
    * 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 ?

leephillips• 17 days ago

Seems clear to me: it’s a silly number that people think is important. Like the Dow, H-index, GNP, ...

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

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