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By default, htop shows colored status bars for processors, memory, and swap. From left to right, the bars are colored green, blue, yellow, and red depending on some thresholds.

What does it mean when the Memory bar has a small level of green and blue, and almost all the remainder is yellow? The swap bar is empty. The color settings for htop are "default".

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2 Answers 2

up vote 84 down vote accepted

Hitting F1 or h will show you the key. But for reference, the default colors are:

CPU:

  • Blue = Low priority threads
  • Green = Normal priority threads
  • Red = Kernel threads

Memory:

  • Green = Used memory
  • Blue = Buffers
  • Yellow/Orange = Cache

There are a couple of different color-schemes available, you can see them through hitting F2.

In your specific case, it means that nearly all of your memory is being used by various OS caches.

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What does orange mean in the CPU bars? Most of my CPU bars are filled with orange, but it doesn't say what it means in the key. –  Etienne Perot May 13 '12 at 19:27
    
@EtiennePerot Perhaps your color setting is different from the default. bbs.archlinux.org/viewtopic.php?id=51818 Moreover htop itself has several color schemes (F2 -> Colors) –  nodakai Oct 10 '12 at 0:40
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@EtiennePerot you are right. There are some more colors. See my answer ;). –  jjmontes Nov 16 '12 at 9:26
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Is it good that a lot of RAM is used by OS caches? Does that make everything faster? The numbers say 1859/8192MB, I guess that excludes the OS cache. Including OS cache the bar is about 4/5 full. Good/bad? –  Rudie Apr 5 '13 at 14:47
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Yes, it's a good thing. See linuxatemyram.com for a good understanding. –  GodsMadClown May 10 '13 at 19:08
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I couldn't find this documented elsewhere. Looking into the code:

There are two modes for CPU metrics reporting: the default one, and a "detailed CPU time" which can be enabled from the Setup screen (Display Options / Detailed CPU time). All of them show the percentage of time spent in different processes:

Default mode

  • Blue: low priority processes (nice > 0)
  • Green: normal (user) processes
  • Red: kernel time (kernel, iowait, irqs...)
  • Orange: virt time (steal time + guest time)

Detailed mode

  • Blue: low priority threads (nice > 0)
  • Green: normal (user) processes
  • Red: system processes
  • Orange: IRQ time
  • Magenta: Soft IRQ time
  • Grey: IO Wait time
  • Cyan: Steal time
  • Cyan: Guest time

Memory meters are more straightforward:

  • Green: Used memory pages
  • Blue: Buffer pages
  • Orange: Cache pages

Note: Info obtained from htop source code at http://htop.svn.sourceforge.net/viewvc/htop/trunk/CPUMeter.c?revision=300&view=markup .

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press F1 for help. –  tgies Mar 20 '13 at 21:53
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