(solved) swap size?

[Spanik]

I just started a new install on the desktop. Reading the handbook, I still come accross:

[Jaglover]

Use swap file(s). You can create and activate them at your will, any time. But watch out, not all filesystems support swap.
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[Ionen]

It still makes some sense if you have some low'ish amount like 1-2GB, but I agree it's a bit of a crude rule by modern standards.

fwiw if you want to do suspend-to-disk you could, in theory, need up to RAM * 1 = 64GB (that's only if you're currently using as much ram, and I imagine it's gonna be pretty slow).

Doesn't hurt to have a little bit of slow swap as a buffer before the OOM killer start killing things either way (even with large amounts of RAM, it's cheap to have a some small 2-6+GB).

[mike155]

If you have 64GB of RAM, you probably won't need any swap space at all.

I haven't had swap on any of my machines for more than 10 years - and I have never missed it.

A swap partition Swap space of at least the size of your RAM is required if you want to use the sleep state 'hibernation'. Do you want to use 'hibernation'?

[Jaglover]

[mike155]

[steve_v]

[Spanik]

[CooSee]

i never used 'swap' since i have 32GB RAM and no problems at all, even with big compiles like 'ungoogled-chromium', while watching stream and browsing through web.

suspend on a desktop system never made sense to me - if i don't use the computer i just shut down.

suspend only makes sense on a notebook.

just my two cents
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[mike155]

I added a comment on the discussion page of our handbook. See: https://wiki.gentoo.org/wiki/Handbook_Talk:AMD64/Installation/Disks, last paragraph.

[Hu]

Both suspend and hibernate make great sense to me. When I don't need my system, I suspend it, so that everything is where I left it when I return. This is more convenient than trying to get every program I use to correctly remember its state and reopen itself on next boot, each with all their interactive per-instance history.

Hibernate is nice for cases where I would suspend, but I expect a thunderstorm to knock out power. Once hibernated, the system can survive a complete loss of wall power during the storm. After the storm passes, I can turn back on and again be where I was.

[CooSee]

thanks @mike155
--

i hope it's ok to ask, but how Apple is handling or using 'suspend', because imho they do it perfectly on their devices.
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" Die Realität ist eine Illusion, die durch Mangel an ehrlicher Kommunikation entsteht "
---
" Der Mensch ist von Natur aus neugierig, was am Ende übrig bleibt ist die Gier "

[steve_v]

[Goverp]

[Hu]

Agreed, power-saving states (both suspend-to-ram and suspend-to-disk) are great for mobile devices, and suspend-to-disk is nice for any device where you know it will be off wall power for long enough that the extra seconds of resuming from disk are worth the battery time saved by not using suspend-to-ram. I was focusing on CooSee's comment that suspend didn't make sense on a desktop, but only made sense on a notebook. I wanted to present cases where suspend makes sense for any device that cannot, on its own, readily restore its state.

I've sometimes seen the hybrid mode referred to as suspend-to-both. That's how sys-power/suspend describes it (via the utility s2both).

[Maffblaster]

I have implemented a table to help readers make a more reasonable choice for swap size:

https://wiki.gentoo.org/index.php?title=Handbook%3AParts%2FBlocks%2FDesigningPartitionScheme&type=revision&diff=1282171&oldid=1214646

Thanks to Mike155 for raising to my attention in the discussion here https://wiki.gentoo.org/wiki/Handbook_Talk:AMD64/Installation/Disks#Recommendation_on_swap_scape_is_outdated
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[figueroa]

I've been working my way down to setting aside less swap. My desktop has 16 GB or RAM and I currently set aside an 8 GB partition for swap on a secondary hard drive. I never see swap actively used, but the system currently has @ 32 MB or swap in -use. There are three large, internal hard drives, all spinning rust, so the disk space isn't much of a consideration.

My home server and home desktop both run 24/7. At night, they do housekeeping chores, including (most importantly) backups. These two computers only get turned off for hardware repair or changing of UPS batteries. However, I do normally shut down all application programs and log off at the end of each day. This leaves my system, the GUI in particular, in a sound, idle state for sane backups. Obviously I don't suspend or hibernate these two machines.

My old and humble notebook, when in use, just gets turned off when not in use, and I have to run backups manually. It only has 4 GB or RAM and a 4 GB swap partition. On the other hand, my wife's main computer is a laptop with 8 GB or RAM. She closes the lid when not in use, which eventually causes it to suspend but not hibernate. She finds it very handy that way. She has a small swap partition just for assurance that it's there when needed. Her backups are triggered by anacron, and she tells me that she doesn't really notice the extra load when backups are taking place. Backups are initially made to an always installed SD card, and then archived to the home server over NFS.

If one does suspend or hibernate (or turn off) their computer, extra consideration should be given to when and how backups are to be made, preferably automatically in some manner.
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amd64/23.0/split-usr/desktop (stable), OpenRC, -systemd -pulseaudio -uefi

[NeddySeagoon]

Swap space is not the kernels only mechanism for swapping.

The swap partition/file is only used as a temporary home for dynamically allocated RAM. That is, things that have no permanent home on storage.
Things like executable code, input data and even output data, can be dropped and reloaded.
Dirty (output) buffers must be flushed before they can be dropped.

This has some interesting side effects.
Programs that cannot be fitted into available RAM cam still be executed. Its OK to mmap the same pages of physical RAM to two (or more) pages of code.
They will be swapped as required. This is slow due the the page faults. But it works.

The same is true with input and output buffers, with the rider that data that is only in RAM must be flushed to disk first.

From the above it follows that not having a swap partition/file only puts pressure on the other 'swapping' mechanisms.

That does not mean that a swap partition/file is required but its a useful diagnostic tool.
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Regards,

NeddySeagoon

Computer users fall into two groups:-
those that do backups
those that have never had a hard drive fail.

[Zucca]