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Htop Explained Visually

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Re: Htop Explained Visually

#31
post #28

what are units of load average?

It's the number of processes either running or waiting in the queue for CPU time. This is averaged over 5, 10, and 15 minutes.

Load of 0 means idle (nothing to run), load of 1 means e.g. one process running and nothing in the queue.

https://en.wikipedia.org/wiki/Load_(computing)

Re: Htop Explained Visually

#32
post #28

what are units of load average?

I can't think of a good way to put it without just giving examples, so here goes: 1.0 = 100% usage of a 1-core system 1.0 = 50% usage of a 2-core system 4.0 = 50% usage of an 8-core system 8.0 = 100% usage of an 8-core system And IIRC, load average is represented usually as 3 numbers, which are over the last 5, 10, and 15 minutes.

> And IIRC, load average is represented usually as 3 numbers, which are over the last 5, 10, and 15 minutes

1, 5 and 15 minutes is the most common intervals

Re: Htop Explained Visually

#33
post #23

I love htop. But I can't figure out a way to disable the CPU monitors. I use a machine with 768 cores which makes it kind of useless.

If you don't mind me asking what kind of machine has 768 cores?

Likely a machine with a group of Xeon Phi coprocessors, each a PCI card containing 64 fully-capable x86 cores: https://www-ssl.intel.com/content/www/us/en/processors/xeon/...

The idea is that you can run embarrassingly parallel workflows without needing to recode for a GPU; just launch processes with appropriate affinities. NERSC has compute clusters with thousands of these beasts. They make astronomers very happy.

Re: Htop Explained Visually

#34

Htop is great! One thing not mentioned in the article is you can interact with htop using the mouse, for example clicking on column headers to sort by that column, or selecting a process. You can get get this mouse support for example by installing the gpm package, which enables the mouse support for the terminal.

gpm is only necessary for interacting with on a Linux TTY; if you are using it in an X terminal emulator, then you merely need a terminal emulator that supports the xterm mouse extensions.

Re: Htop Explained Visually

#35
post #32

Earlier quoted context omitted.

I can't think of a good way to put it without just giving examples, so here goes: 1.0 = 100% usage of a 1-core system 1.0 = 50% usage of a 2-core system 4.0 = 50% usage of an 8-core system 8.0 = 100% usage of an 8-core system And IIRC, load average is represented usually as 3 numbers, which are over the last 5, 10, and 15 minutes.

> And IIRC, load average is represented usually as 3 numbers, which are over the last 5, 10, and 15 minutes 1, 5 and 15 minutes is the most common intervals

The load average is calculated by the kernel (processes that display it just regurgitate the first 3 columns from /proc/loadavg); and yes, it is 1, 5, and 15 minutes.

Re: Htop Explained Visually

#36
post #5

As a consequence of trying htop after a long time, I got a reminder that VIRT is not related to RES. I noticed Libreoffice Calc with 29.7 GB of virtual memory and only 198 MB actually used. I wonder why LO made a malloc of nearly 30 GB, but memory is cheap especially because it's virtual. The next one on the list is Firefox with 8.5 GB VIRT and 994 MB RES. By the way, I've got 16 GB of RAM and no swap. Anyway all tha…

At a guess: LO is requesting (via mmap) enough memory up front to represent a full spreadsheet with data in every cell from A1 to the bottom-right corner, and letting the OS supply pages for the small parts of the spreadsheet that are actually accessed. AIUI this is a common technique for big sparse arrays.

Re: Htop Explained Visually

#39
post #24

I love htop. But I can't figure out a way to disable the CPU monitors. I use a machine with 768 cores which makes it kind of useless.

Open `~/.config/htop/htoprc` and modify the line: left_meters=AllCPUs Memory Swap to be left_meters=CPU Memory Swap That will replace the default CPU monitor with a single meter for the average across all cores. After that, you'll be able to customize things the standard way by pressing F2 within htop.

Excellent, this worked!

Re: Htop Explained Visually

#40
post #33
post #23

Earlier quoted context omitted.

If you don't mind me asking what kind of machine has 768 cores?

Likely a machine with a group of Xeon Phi coprocessors, each a PCI card containing 64 fully-capable x86 cores: https://www-ssl.intel.com/content/www/us/en/processors/xeon/... The idea is that you can run embarrassingly parallel workflows without needing to recode for a GPU; just launch processes with appropriate affinities. NERSC has compute clusters with thousands of these beasts. They make astronomers very happy.

Actually a NUMA system, an SGI UV: https://www.sgi.com/products/servers/uv/
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