How big should my swap partition be?

[d2_racing]

[eccerr0r]

Is there a Gentoo FAQ about swap somewhere?

How much swap you need depends on how you use your computer. Gentoo installations are a bit different as everyone will be compiling for the most part.

Key things:
1) how much ram you have
2) how much ram you typically use (all applications, including allocated but unused RAM)
3) using tmpfs to build? (ramdisk)
4) how fast is your disk (see #5)
5) your tolerance for pain

If you want to emerge anything at all, I think a safe number is you must have minimal 512MB of memory, whether it's made of physical RAM or swap. However, if you have less than 1/4 real RAM, this may hit the "pain tolerance" fast and having that much would be counterproductive. If you have a fast disk your tolerance for swap may be higher. If you want to run with -j to use more cores, you may need to multiply this by the number of jobs you have running at once.

Now if you use X11 and GUIs a lot you need to add more to this 512MB number, say another 512M or so. I think it is possible to run a Gentoo system with no swap with 1GB RAM if you're *very* careful, but 512MB for the GUI/etc may be optimistic.

At 2 or 4GB RAM there may be temptation to use tmpfs. This will take away from your normal use, so however big your tmpfs gets you need to add this to your working space (ram+swap).

I'd say at 1GB or more, if you want to play chicken with your RAM, you don't need swap. Else I think it's best to add some swap as long as you can afford the disk space. Most people with large mechanical disks, there's no reason why not to have swap space.

It's a touchy feely guess. I normally just do:
if RAM <= 512MB then swap=2X RAM
else if using(SuspendToDIsk) then swap = 2X RAM
else SWAP=1GB

This is NOT a good heuristic. Depending on your utilization it may not be enough swap or too much. I use an 8G machine at work and have gone 3-4GB deep into swap. The machine is still very responsive -- and the disk isn't thrashing. If I didn't have the swap enabled, the program would have died and I would have had to beg for more RAM...
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[akbarstatx]

I still use create a swap file system. Even when the box has 4GB+ ram. I don't always make it twice the ram but usually 1G. The reason is if by some wierd chance you do run out of ram memory and you don't have swap space the kernel will crash but If you a little swap, I don't think size matters here the kernel will not crash but just run very slowly.

[aidanjt]

[yngwin]

[d2_racing]

Thanks yngwin, I will keep that in mind.

[NathanZachary]

Since I don't use suspend to disk, I have my swap partition set to a really low amount. I only have 1GiB of RAM, but I still only have a 128MiB swap partition. I haven't run into any problems, and this system has been running for years. Of course, it is completely dependent on your typical usage (as others have mentioned).
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[milomak]

[d2_racing]

In fact, 12 Gig of SWAP is too high

[gruber]

Yep!

I'm with 3GB RAM (because of the @#$& WinXP 32bit). On my I have a small swap only because I let Ubuntu do it. Nevertheless, Neither Ubuntu or Gentoo actually ever swapped something. And I'm using some FFTs which can eat-a-lot. My newest gentoo install is with no swap at all and still works with no need of one.

So, if you're using desktop system for regular use (gaming, office, net) and you don't want suspend-to-disk, you don't need swap. IMHO!!!

If you want to do some sci jobs, heavy gimp-ing, etc, do some swap. IMHO!!!

[d2_racing]

Maybe 1 Gig of swap is enough if you don't use suspend to ram feature

[ruivilela]