I configured 4GB of RAM memory and the OS is only using 2GB. How to release 100% usage? Whenever I increase the capacity of the OS, it is only limited to 50% of its capacity.

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root@ucs-1198:~# uname -a
Linux ucs-1198 4.19.0-23-amd64 #1 SMP Debian 4.19.269-1 (2022-12-20) x86_64 GNU/Linux
  • what do you mean with "the OS is only using 2GB"? That's plain not true, as your display even shows. Nothing here indicates any limitation in "capacity", whatever you mean with that! Aug 29, 2023 at 16:02
  • What is that screenshot supposed to show? You seem to be using 2.58 GB out of 3.84 GB. What do you expect to see?
    – Kusalananda
    Aug 29, 2023 at 16:03
  • @roaima I thought in that direction as well, but then I tried to read the dark gray on black background in the "Mem" meter. This is all fine, the problem seems to be one that we don't understand yet, or a misunderstanding on the side of the user! Aug 29, 2023 at 16:03
  • @Kusalananda Although it looks like it's using memory correctly, it's being limited. The htop bar should be at least in the middle. Note that the bar represents 100%. If you're using just over 2GB, it shouldn't be touching the other end, which is like 100% of the bar. Aug 29, 2023 at 16:28
  • 2
    What does free -m command return?
    – nobody
    Aug 29, 2023 at 16:44

1 Answer 1


In htop, the colours are significant. The value shown on the right (2.58G) corresponds to the green part of the bar, and reflects the memory currently used by programs.

The blue part of the bar represents “buffers”, and the yellow or brown part represents cache (see the htop FAQ). It’s common for the bar overall to reach 100% or close, because the Linux kernel tries to use as much physical memory as is useful — not just to satisfy running programs’ memory requirements, but also to avoid repeated I/O.

Note too that some programs will by default limit their memory use to around half the installed physical memory; this can happen in particular with JVM-based programs. If you see performance problems related to this you’ll have to tune the relevant program’s configuration.

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