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Nux
Asked: 2024-10-25 20:59:48 +0800 CST

Is swap memory required when using Postgres on Linux?

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So, my friend says swap is an old concept and shouldn't be needed on new systems as long as you have enough RAM. But then I heard suggestions that swap might actually be required when using Postgres on Linux or even Unix because malloc/free will not return memory to the system. I'm told this is a feature, not a bug, and I should use swap because system will use swap for the freed memory... Is this correct or am I missing something? Can someone confirm this and maybe shed more light on it?

My setup for context:

  • PGSQL config: shared_buffers + (temp_buffers + work_mem) * max_connections = 20 GB;
  • PGSQL is version 16, the server in on Ubuntu 22.
  • The server has 50 GB of RAM and 0 swap. ZFS ARC is maxed out at 8 GB.
  • I'm actually seeing 20 GB surpassed after a few hours.
  • I see bumps in RAM usage each day. 50 GB is reached within 5-7 days (drops to 0 on PGSQL restart).

That's the context. Essentially, the question is: do I need to, or should I, have swap for a VM with Postgres server or not?

linux

1 Answers

  1. Best Answer

    It’s actually safer to have some swap space so that when the system runs out of physical memory, it will experience a slowdown instead of immediately killing processes. In short, in modern systems, swap space acts as insurance you’ll probably never need.

    A similar discussion with many arguments can be found here:

    https://community.nethserver.org/t/linux-swap-needed-or-not/23655

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