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804 points jryio | 2 comments | 21 Oct 25 20:28 UTC | HN request time: 0.001s | source

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speedgoose ◴[21 Oct 25 21:12 UTC] No.45661785[source]▶

Looking at the htop screenshot, I notice the lack of swap. You may want to enable earlyoom, so your whole server doesn't go down when a service goes bananas. The Linux Kernel OOM killer is often a bit too late to trigger.

You can also enable zram to compress ram, so you can over-provision like the pros'. A lot of long-running software leaks memory that compresses pretty well.

Here is how I do it on my Hetzner bare-metal servers using Ansible: https://gist.github.com/fungiboletus/794a265cc186e79cd5eb2fe... It also works on VMs.

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levkk ◴[21 Oct 25 21:51 UTC] No.45662183[source]▶

>>45661785 #

Yeah, no way. As soon as you hit swap, _most_ apps are going to have a bad, bad time. This is well known, so much so that all EC2 instances in AWS disable it by default. Sure, they want to sell you more RAM, but it's also just true that swap doesn't work for today's expectations.

Maybe back in the 90s, it was okay to wait 2-3 seconds for a button click, but today we just assume the thing is dead and reboot.

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bayindirh ◴[21 Oct 25 22:15 UTC] No.45662411[source]▶

>>45662183 #

This is a wrong belief because a) SSDs make swap almost invisible, so you can have that escape ramp if something goes wrong b) SWAP space is not solely an escape ramp which RAM overflows into anymore.

In the age of microservices and cattle servers, reboot/reinstall might be cheap, but in the long run it is not. A long running server, albeit being cattle, is always a better solution because esp. with some excess RAM, the server "warms up" with all hot data cached and will be a low latency unit in your fleet, given you pay the required attention to your software development and service configuration.

Secondly, Kernel swaps out unused pages to SWAP, relieving pressure from RAM. So, SWAP is often used even if you fill 1% of your RAM. This allows for more hot data to be cached, allowing better resource utilization and performance in the long run.

So, eff it, we ball is never a good system administration strategy. Even if everything is ephemeral and can be rebooted in three seconds.

Sure, some things like Kubernetes forces "no SWAP, period" policies because it kills pods when pressure exceeds some value, but for more traditional setups, it's still valuable.

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1. eru ◴[21 Oct 25 23:48 UTC] No.45663237[source]▶

>>45662411 #

How long is long running? You should be getting the warm caches after at most a few hours.

> Secondly, Kernel swaps out unused pages to SWAP, relieving pressure from RAM. So, SWAP is often used even if you fill 1% of your RAM. This allows for more hot data to be cached, allowing better resource utilization and performance in the long run.

Yes, and you can observe that even in your desktop at home (if you are running something like Linux).

> So, eff it, we ball is never a good system administration strategy. Even if everything is ephemeral and can be rebooted in three seconds.

I wouldn't be so quick. Google ran their servers without swap for ages. (I don't know if they still do it.) They decided that taking the slight inefficiency in memory usage, because they have to keep the 'leaked' pages around in actual RAM, is worth it to get predictability in performance.

For what it's worth, I add generous swap to all my personal machines, mostly so that the kernel can offload cold / leaked pages and keep more disk content cached in RAM. (As a secondary reason: I also like to have a generous amount of /tmp space that's backed by swap, if necessary.)

With swap files, instead of swap partitions, it's fairly easy to shrink and grow your swap space, depending on what your needs for free space on your disk are.

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2. bayindirh ◴[22 Oct 25 10:55 UTC] No.45667275[source]▶

>>45663237 (TP) #

> Yes, and you can observe that even in your desktop...

Yup, that part of my comment was culmination of using Linux desktops for the last two decades. :)

> I wouldn't be so quick. Google ran their servers without swap for ages.

If you're designing this from get go and planning accordingly, it doesn't fit into my definition of eff it, we ball, but let's try this and see whether we can make it work.

> With swap files, instead of swap partitions,...

I'm a graybeard. I eyeball a swap partition size while installing the OS, and just let it be. Being mindful and having good amount of RAM means that SWAP acts as a eviction area for OS first, and as an escape ramp second, in very rare cases.

Sent from my desktop.

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