Can you set up a RAM drive that automatically expands and shrinks as needed to temporarily store files?

General Question

I think it'd be really cool if I could drag and drop files directly into my RAM, so that I could access these files more quickly when performing I/O-intensive operations on them, or if I'm on a machine with limited storage and I want a temporary place to put things for whatever reason.

I could see it being especially useful for opening large archives.

Is there a way to set this up in EndeavourOS? IIRC, ramdrives are possible in Linux, but I don't know if you can set one up that only uses up as much RAM as you need it to.

EDIT: So I decided to give ramfs a try first. Turns out Dolphin doesn't know how to work with ramfs, at least not very well. I can use Dolphin to create folders on a ramfs mount, as well as to open files I copied there through the terminal, but I can't use Dolphin itself to copy files to a ramfs mount.

With tmpfs on the other hand, Dolphin seems to work fine, and it has the added benefit of being able to mount automatically through fstab with ownership assigned to my user.

Here's the fstab entry I'm currently using:

none /mnt/tmpfs2 tmpfs nofail,nodev,nosuid,noexec,noatime,mode=0700,uid=1000,gid=1001,size=16384M 0 0

in EndeavourOSby mr_bigmouth_502KDE Plasma

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BCMM

15d

Yes, this is exactly what tmpfs does (or, I suppose, ramfs - if you want to absolutely guarantee that those files stay in physical RAM even at the expense of system stability).

However, what exactly do you want this for?

so that I could access these files more quickly when performing I/O-intensive operations on them

When you read or write a file on a conventional on-disk filesystem, Linux keeps a copy in RAM anyway (in the page cache). This means, for example, that if you save a large archive to your downloads and then open it in an archiver application, and you have enough free RAM to hold it, then it is already in RAM and your archiver will open just as fast as if you saved it to a tmpfs.

As such, tmpfs is mostly useful if the file really is temporary, and you will not ever need to write it out to disk.

There is, perhaps, a more fringe use for it, which is when you're not going to do the second I/O-intensive task immediately after the first one, and you want to make sure that your data does not get replaced, in the page cache, by some other files in the meantime.

Using a tmpfs like this is equivalent to asserting that you have a better idea of what it is efficient to cache than the Linux memory management subsystem. The other I/O tasks you perform in the meantime may very well perform worse, because you have taken away some RAM that would otherwise have been used by the page cache. You may well be right, but you should be aware of that trade-off and check that it's actually worthwhile.

mr_bigmouth_502

KDE Plasma

15d

However, what exactly do you want this for?

so that I could access these files more quickly when performing I/O-intensive operations on them

That, and for fun. One of my favorite things about using Linux (and computers in general) is tinkering with it and getting it to do crazy things.

There is, perhaps, a more fringe use for it, which is when you're not going to do the second I/O-intensive task immediately after the first one, and you want to make sure that your data does not get replaced, in the page cache, by some other files in the meantime.

Using a tmpfs like this is equivalent to asserting that you have a better idea of what it is efficient to cache than the Linux memory management subsystem. The other I/O tasks you perform in the meantime may very well perform worse, because you have taken away some RAM that would otherwise have been used by the page cache. You may well be right, but you should be aware of that trade-off and check that it's actually worthwhile.

Sounds like a fair price to pay, especially if I use a ramfs rather than a conventional tmpfs (which, I'm aware isn't as safe.)

But yeah, the way I see it, putting stuff in tmpfs/ramfs is basically me manually reallocating my system's resources for what I think it should be focused on. Plus, isn't using RAM as temporary storage just plain cool?