Re: [gentoo-user] Memory manager

[Mick]

On Saturday, 19 October 2019 14:11:26 BST mad.scientist.at.large@××××××××.com 
wrote:
> Do systems run different memory management when swap is on versus no swap?

The answer to this question is an unqualified yes, although you do not define 
your meaning of "different memory management".  The existence of swap space 
and the kernel's swappiness setting will change the way memory is dynamically 
allocated to processes at runtime and may affect the responsiveness of your 
system.

However, you may not experience any difference by having swap on, if your 
swappinness setting is low and in addition you never run a high enough number 
of memory hungry processes to consume all available RAM.


> I know that in the past it was recommended to have at least a small swap so
> the system used a better memory manager.  Wondering specifically if I
> should set up a small ram drive for swap just to get better memory
> management or if I should run swapless as this particular machine has a
> slightly obscene amount of ram available so I shouldn't need a proper swap
> partition unless it affects memory management.
>
> -- “The whole world is watching! The whole world is watching!”

The handbook recommendation to set up a swap space (partition) is probably 
made as a low cost, safe configuration to have, which may even save your bacon 
one day.  It is conceivable you could set portage to run a large enough number 
of jobs on a memory hungry compile, e.g. chromium, to end up with no memory 
left.  In addition, if you tried to Suspend-to-RAM, at a point when all of 
your RAM is being used, you would soon discover you can't do it without any 
swap space made available.  If you hibernate, then a swap space (file/
partition) will be used, which makes it reasonable to have a swap space set up 
for this purpose in advance.  For a desktop, the relative low cost of disk 
space today suggests it is a good idea to set up some swap space, even if you 
hardly ever going to use it.

With the arrival of SSDs the usage of swap was discouraged, because repeated 
read/writes tended to age prematurely the (early) SSDs.  I still use spinning 
disks for swap, but I don't know what the prevailing wisdom/experience suggest 
these days.

Have a look at this for generalities:

https://wiki.gentoo.org/wiki/Knowledge_Base:Is_swap_space_really_necessary


And this for an alternative, or complimentary solution:

https://wiki.gentoo.org/wiki/Zram

-- 
Regards,

Mick