1y ago

Ubuntu 24.04 increases vm.max_map_count for smoother Linux gaming

www.gamingonlinux.com

Gaming @lemmy.zip

Zippy Bot @lemmy.zip

BOT

1y ago

Ubuntu 24.04 increases vm.max_map_count for smoother Linux gaming

www.gamingonlinux.com /2024/03/ubuntu-2404-increases-vm-max-map-count-for-smoother-linux-gaming/

23 comments

What I always wonder with things like this, what is the downside? There must be a reason why that value was set lower.
- Hastily read around in the related issue-threads and seems like on it's own the vm.max_map_count doesn't do much... as long as apps behave. It's some sort of "guard rail" which prevents processes of getting too many "maps". Still kinda unclear what these maps are and what happens is a process gets to have excessive amounts.
  That said: https://access.redhat.com/solutions/99913
  According to kernel-doc/Documentation/sysctl/vm.txt:
  This file contains the maximum number of memory map areas a process may have. Memory map areas are used as a side-effect of calling malloc, directly by mmap and mprotect, and also when loading shared libraries.
  While most applications need less than a thousand maps, certain programs, particularly malloc debuggers, may consume lots of them, e.g., up to one or two maps per allocation.
  The default value is 65530.
  Lowering the value can lead to problematic application behavior because the system will return out of memory errors when a process reaches the limit. The upside of lowering this limit is that it can free up lowmem for other kernel uses.
  Raising the limit may increase the memory consumption on the server. There is no immediate consumption of the memory, as this will be used only when the software requests, but it can allow a larger application footprint on the server.
  So, on the risk of higher memory usage, application can go wroom-wroom? That's my takeaway from this.
  edit: ofc. I pasted the wrong link first. derrr.
  edit: Suse's documentation has some info about the effects of this setting: https://www.suse.com/support/kb/doc/?id=000016692
  
  The default value is 65530
  Just checked and the steam deck has it set to 2147483642. My gentoo systems are 65530.
  
  no, it'll go vroom-vroom
  
  My read is that it matters for servers where a large number of allocations could indicate a bug/denial of service, so it's better to crash the process.
  That's not relevant on a gaming system, since you want one process to be able to use all the resources.
- It changed it for playing "the finals" some weeks ago to fix a crash. I havent had any issues with my system since then so it really might just be some value that never changed because nothing needed it.
- What should it be set to?
  The steam deck has it set to 2147483642.
  
  Also known as (close) to max signed int32
  
  That's also the default value on Garuda (arch-based, gaming-oriented)
- To 1048576.
this is great, my lug has a script we have to share around for new Linux users to increase this and it will be nice with more distros having this set high by default
- Arch is having internal discussions to increase it. Might be something upstream may adopt if all major distributions end up increasing it.
Raise it ! There is only benefits for your gaming experience in Linux.
Fedora changed it as well some time back you can use sudo sysctl -w vm.max_map_count=2147483642 to match the SteamDeck with Fedora.
@mr_MADAFAKA@lemmy.ml I saw that you shared it on reddit earlier, but the post is gone, did the mods just nuke it?
- I delete it, was looking through some old post and accidentally delete it
  
  Ah okay, thought the mods were doing their thing again, they do keep removing gol posts <_<, i deleted my reddit account - all in on lemmy and fediverse now (but appreciate you sharing it there!)

23 comments