If you’re not aware of what preload is, it’s a command line application that allows you to add files to ram, so they can be accessed faster by the applications that need them.
It seems to work well for what I’m using it for, which is to run games from slower storage devices, but there doesn’t seem to be any documentation for a proper way to remove the files once they’ve been added to ram. What I’ve been doing is to just use htop to terminate the preload command, but I feel like this is not intended at all. Is there a better way to remove these files?
I should mention that while trying to search for a solution myself, I did see gopreload mentioned a few times. I would try this out myself, but there’s no proper installation instructions, at least not any I could find that work in Linux Mint.
Are we talking about this preload?
https://manpages.ubuntu.com/manpages/jammy/man8/preload.8.html
Cause if so, it doesn’t actually let you manually add specific files to RAM. It’s an adaptive daemon that automatically learns which files your applications use frequently over time and prefetches them. So when you launch it and then play games, it’s observing patterns and making predictions.
This also explains why there’s no “remove files” command. The files preload loads into RAM aren’t locked there; they’re in the page cache, which the kernel manages freely. If something else needs that memory, the kernel will evict those cached files automatically. Killing preload via htop should not really do anything, except it not doing it’s thing anymore.
When I used preload, it let me manually add files to ram. I used
sudo preload filenamefor each file (the game I tried it with only had two) and it seemed to add them to ram. I know this because the game had hitching issues even after just adding the main executable but the hitching went away when I added the second file.When you open and read files from a program the OS (kernel) will typically cache part or all of those files in memory. This is to speed up subsequent reads of that file since disk access is slow.
“preload” seems to be making use of that feature.
The kernel maintains this cache and evicts (unloads) things from it as needed. You don’t need to worry about it.
After doing some more “extreme” tests, it seems like I was wrong about how preload works. In fact, it didn’t seem to actually preload the files at all, so I’m not sure what it actually does. I ran
sudo sysctl vm.drop_caches=1to make sure that none of the game’s files were loaded and then used preload like I did yesterday, but the game still has hitching issues. This means that the game’s files were probably still loaded in RAM when I was trying it yesterday.This doesn’t really prove it.
Running ths game multiple times will do the same, because the pages will stay cached. Operating systems are smart with RAM. Things that were recently used stay in RAM, even though the OS reports it being “free”. Read this for some more info: https://www.linuxatemyram.com/
And preload might swallow the filepath arg without doing anything with it.
Instead you could share the output of
preload --help preload --version sudo preload --verbose # followed by running a gameWhat you describe can actually be done with another tool https://hoytech.com/vmtouch but not with preload.
After trying vmtouch, it only seems to be partially helping. I’m not sure if I’m just using it incorrectly or not but if I remove the files from RAM and then use vmtouch to add them back in, the hitching issues are still partially there.
To fully explain what my issue is, I currently using the Linux version of the Cyber Lancer demo from Itchio as it’s small enough to fit onto my 128 MB SD card, which is very slow. I can easily run the game from other storage devices that have much higher read speeds but I want to get the most out of my older and slower storage devices. What’s happening is when the game first loads when it’s files aren’t stored in RAM, is the game essentially freezes for a split second every time it has to load an asset that wasn’t previously loaded.
vmtouch isn’t making the hitching go away, it just making it load a little faster. This does mean that it’ll help but if you’re aware of a better solution, I can try that out as well.
That wont be necessary, after doing more “extreme” tests with preload, it seems like I was wrong about preload. I used
sudo sysctl vm.drop_caches=1to make sure that none of the game’s files were loaded in RAM before using preload like I did yesterday, but the game still has hitching issues. This means that the game’s files were probably still loaded in RAM when I was testing it yesterday.For context, what I’m trying to do is find a way to run smaller games more smoothly from some very old storage devices that are very slow. I thought that preload would be the solution but since it doesn’t seem to actually do what I thought it did, I’m going to need a different solution. I will try vmtouch and respond back if it works.