6 ms·

I dont get why anti-swap is so prevalent in Linux discussions. Like, what does it hurt to stick 8-16-32gb extra "oh fuck" space on your drive. Either you're go

I dont get why anti-swap is so prevalent in Linux discussions. Like, what does it hurt to stick 8-16-32gb extra "oh fuck" space on your drive. Either you're going to never exhaust your system ram, so it doesn't matter, minimally exhaust it and swap in some peak load but at least nothing goes down, or exhaust it all and start having things get OOM'd which feels bad to me. Am I out of touch? Surely it's the children who are wrong.

man8alexd 9mo ago
8-16-32gb of swap space without cgroup limits would get the system into swap thrashing and make it unresponsive.
ch_123 9mo ago
I think it's some kind of misplaced desire to be "lightweight" and avoid allocating disk space that cannot be used for regular storage. My motivation way back when for wanting to avoid swap was due to concerns about SSD wear issues, but those have been solved for a long time ago.
manuel_w 9mo ago
The pro-swap stance has never made sense to me because it feels like a logical loop. There’s a common rule of thumb that says you should have swap space equal to some multiple of your RAM. For instance, if I have 8 GB of RAM, people recommend adding 8 GB of swap. But since I like having plenty of memory, I install 16 GB of RAM instead—and yet, people still tell me to use swap. Why? At that point, I already have the same total memory as those with 8 GB of RAM and 8 GB of swap combined. Then, if I upgrade to 24 GB of RAM, the advice doesn’t change—they still insist on enabling swap. I could install an absurd amount of RAM, and people would still tell me to set up swap space. It seems that for some, using swap has become dogma. I just don’t see the reasoning. Memory is limited either way; whether it’s RAM or RAM + swap, the total available space is what really matters. So why insist on swap for its own sake?
- man8alexd 9mo ago
  This rule of thumb is outdated by two decades. The proper rule of thumb is to make the swap large enough to keep all inactive anonymous pages after the workload has stabilized, but not too large to cause swap thrashing and a delayed OOM kill if a fast memory leak happens.
  - tremon 9mo ago
    That's not useful as a rule of thumb, since you can't know the size of "all inactive anonymous pages" without doing extensive runtime analysis of the system under consideration. That's pretty much the opposite of what a rule of thumb is for.
    - man8alexd 9mo ago
      You are right, it is not a rule of thumb, and you can't determine optimal swap size right away. But you don't need "extensive runtime analysis". Start with a small swap - a few hundred megabytes (assuming the system has GBs of RAM). Check its utilization periodically. If it is full, add a few hundred megabytes more. That's all.
      - ZoomZoomZoom 9mo ago
        It's not like it's easy to shuffle partitions around. Swap files are a pain, so you need to reserve space at the end of the table. By the time you need to increase swap the previous partition is going to be full. Better overcommit right away and live with the feeling you're wasting space.
        man8alexd 9mo ago
        Exactly opposite. Don't use swap partitions, and use swap files, even multiple if necessary. Never allocate too much swap space. It is better to get OOM earlier then to wait for unresponsive system.
direwolf20 9mo ago
Swap causes thrashing, making the whole system unusable, instead of a clean OOM kill
- man8alexd 9mo ago
  swap causes thrashing if you have too large swap and no cgroup limits.
- NekkoDroid 9mo ago
  IMO OOM killing should be reserved for single processes misbehaving. When a lot of different applications just use a decent amount of memory and exhaust the system RAM swapping to disk is the appropriate thing to do.
  - man8alexd 9mo ago
    When you set cgroup limits, you tell the kernel how to determine when a process is misbehaving and needs to be OOM-killed.
AtlasBarfed 9mo ago
1) in the Microsoft days I would have a lot of available ram, bur windows still would aggressively swap, and I would get enraged when changing to an app that would have to swap in while I had 4gb of memory free 2) the os tried to be magical, but a swap thrash is still crap... I would much rather oom kill apps than swap thrash. For a desktop user: kill the fucking browser or electron apps, don't freeze the system/ui.

man8alexd 9mo ago

8-16-32gb of swap space without cgroup limits would get the system into swap thrashing and make it unresponsive.

ch_123 9mo ago

I think it's some kind of misplaced desire to be "lightweight" and avoid allocating disk space that cannot be used for regular storage. My motivation way back when for wanting to avoid swap was due to concerns about SSD wear issues, but those have been solved for a long time ago.

manuel_w 9mo ago

The pro-swap stance has never made sense to me because it feels like a logical loop. There’s a common rule of thumb that says you should have swap space equal to some multiple of your RAM. For instance, if I have 8 GB of RAM, people recommend adding 8 GB of swap. But since I like having plenty of memory, I install 16 GB of RAM instead—and yet, people still tell me to use swap. Why? At that point, I already have the same total memory as those with 8 GB of RAM and 8 GB of swap combined. Then, if I upgrade to 24 GB of RAM, the advice doesn’t change—they still insist on enabling swap. I could install an absurd amount of RAM, and people would still tell me to set up swap space. It seems that for some, using swap has become dogma. I just don’t see the reasoning. Memory is limited either way; whether it’s RAM or RAM + swap, the total available space is what really matters. So why insist on swap for its own sake?

man8alexd 9mo ago
This rule of thumb is outdated by two decades. The proper rule of thumb is to make the swap large enough to keep all inactive anonymous pages after the workload has stabilized, but not too large to cause swap thrashing and a delayed OOM kill if a fast memory leak happens.
- tremon 9mo ago
  That's not useful as a rule of thumb, since you can't know the size of "all inactive anonymous pages" without doing extensive runtime analysis of the system under consideration. That's pretty much the opposite of what a rule of thumb is for.
  - man8alexd 9mo ago
    You are right, it is not a rule of thumb, and you can't determine optimal swap size right away. But you don't need "extensive runtime analysis". Start with a small swap - a few hundred megabytes (assuming the system has GBs of RAM). Check its utilization periodically. If it is full, add a few hundred megabytes more. That's all.
    - ZoomZoomZoom 9mo ago
      It's not like it's easy to shuffle partitions around. Swap files are a pain, so you need to reserve space at the end of the table. By the time you need to increase swap the previous partition is going to be full. Better overcommit right away and live with the feeling you're wasting space.
      - man8alexd 9mo ago
        Exactly opposite. Don't use swap partitions, and use swap files, even multiple if necessary. Never allocate too much swap space. It is better to get OOM earlier then to wait for unresponsive system.

direwolf20 9mo ago

Swap causes thrashing, making the whole system unusable, instead of a clean OOM kill

man8alexd 9mo ago
swap causes thrashing if you have too large swap and no cgroup limits.
NekkoDroid 9mo ago
IMO OOM killing should be reserved for single processes misbehaving. When a lot of different applications just use a decent amount of memory and exhaust the system RAM swapping to disk is the appropriate thing to do.
- man8alexd 9mo ago
  When you set cgroup limits, you tell the kernel how to determine when a process is misbehaving and needs to be OOM-killed.

AtlasBarfed 9mo ago

1) in the Microsoft days I would have a lot of available ram, bur windows still would aggressively swap, and I would get enraged when changing to an app that would have to swap in while I had 4gb of memory free 2) the os tried to be magical, but a swap thrash is still crap... I would much rather oom kill apps than swap thrash. For a desktop user: kill the fucking browser or electron apps, don't freeze the system/ui.