(Gentoo)Help me reduce my boot up memory usage
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Well I wasn't thinking about memory (and maybe that's the reason some people downvoted that comment...) but because in my experience NetworkManager takes time starting at boot and with months/years it was taking more and more time. I reset it once and kept doing the same thing.
As you said you're planning on a home server kind of thing I'd think setting up a static ip is a good idea and NetworkManager is just an overkill for that - you could very well go along with Gentoo's netifrc.
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Uh, memory metrics in Linux are a pain. The only tool that reports most cached as available is htop. free, top and a lot of other software (like node_exporter) will report that a lot of cached memory is not available.
To OP: don’t worry, a lot of Linux tools are smart enough to give back memory if memory pressure rises.
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MEM% for each NetworkManager process is 0.4 % of 3.28 G ≈ 13.1 M. Additionally, almost certainly most of this will be shared between these process, as well as other processes, so you cannot just add them together.
The virtual size (350M) is the allocated virtual memory. quite clearly only 13.1 M of this are actually in use. The rest will only start getting backed by real physical memory if it is being written to.
The way this works is that the process will get interrupted if it writes to a non-physical memory location (by the memory management unit (MMU); this is known as a page fault), and executions jumps to the kernel which will allocate physical memory and alter the virtual memory table, and then proceed with the execution of the write operation.
Many programs or library functions like to get way larger virtual memory buffers than they will actually use in practice, because that way the kernel does all this in the background if more memory is needed, and the program doesn't need to do anything. I.e. it simplifies the code.
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Remove Modemmanager if you don't use it, replace Network-manager and wpa_supplicant with connman or iwd, maybe look if you can remove elogind since you already use seatd.
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The memory is available if applications need it
That's not true, since it's reserved memory.
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Rimworld mods sometime occupy 10gb RAM after a crash/force-close. That one helps.
But don't set up a cronjob running it regularly, that causes issues.
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Reserved memory
Some times. This is actually where we run into one of the issues with open source software, competing standards. Some tools will call your swap or cache "reserved" regardless if it's actually being used or not. They're not wrong, it is reserved, but it's reserved for usage in emergency situations rather than being reserved in the way we look at the rest of memory
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This is from btop.
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I've used swap on my steamdeck for a while and it's really only improved performance in memory-bound situations when I've used it.
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Iwd is so smooth to use
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You mention this is a server VM and so you probably don't need NetworkManager or the wpa_supplicant services. If you don't wish to setup a static IP for the server VM then install and use dhcpcd instead of NetworkManager/wpa_supplicant.
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Unless you need to use WWAN (2G/3G/4G/5G) devices, you don't need ModemManager.
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Depending on your workflow, consider reducing the number of agetty instances to 1. With a single agetty instance, install and use tmux multiplexer when you need more sessions on the physical VM console.
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I don't have any experience of using seatd/elogind but I think you may be able to configure USE flags such that you only need seatd installed (i.e. don't need elogind) and since you need seatd only for running a WM occasionally, why not use seatd-launch to start the WM and not have the seatd daemon running constantly. See: https://github.com/swaywm/sway/wiki/Running-Sway-with-seatd,-elogind-or-systemd‐logind#seatd-launch
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Lastly, the largest chunk of memory used other than the processes you can see in htop will be the Linux kernel. The Gentoo distribution kernel will have hundreds of drivers for real hardware which make no sense in a Kernel that will be used in a VM (unless you plan to use PCI/USB pass through). So, you should create a custom kernel (https://wiki.gentoo.org/wiki/Kernel/Gentoo_Kernel_Configuration_Guide) which is tailored for a KVM guest.
To do this (the following are not detailed instructions but just guidance):
- You start with "make defconfig" which creates a ".config" file with the default options from the ARCH supplied defconfig (e.g. x86_64_defconfig).
- Then you do a "make kvm_guest.config" which adds config options that makes the kernel bootable as a KVM guest.
- Next you need to do a "make filesystem.config" which will add config options for filesystems you need the kernel to support. (* see note below)
- Next you need to do a "make systemd.config" which will add config options for systemd functionality related support. (* see note below)
- Next you need to do a "make arch_x86.config" which will enable additional config options for some virtual hardware support drivers (* see note below)
Note 1: The additional "*.config" files mentioned above will need to be copied into the correct place before make will find them and I've provided some some sample config files you can use to start with below:
- https://github.com/torvalds/linux/blob/master/kernel/configs/kvm_guest.config
- https://github.com/cyano-linux/qemu-guest-kernel/blob/master/filesystem.config
- https://github.com/cyano-linux/qemu-guest-kernel/blob/master/systemd.config
- https://github.com/cyano-linux/qemu-guest-kernel/blob/master/arch_x86.config
Note 2: I'm not associated with the above github repo(cyano-linux/qemu-guest-kernel) but I have referenced it when I needed to setup a custom kernel. You can find a little documentation for the above kernel config here: https://github.com/cyano-linux/qemu-guest-kernel/blob/master/config.md
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Not really. Doesn't sound like they are having any problems.
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You might be a little surprised at how much compute goes into running a modern farm.
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Thank you for explaining it. I haven't been in the *nix world for years, keep thinking I'll get back into it.
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I said it was significant, not that they were having problems.
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If they're not having problems then why investigate?
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I rather let it fucks my CPU than let my whole computer fucks itself
