[talk] Does swap still matter?

Pete Wright pete at nomadlogic.org
Wed Mar 16 17:26:16 EDT 2022

On 3/16/22 08:03, George Rosamond wrote:
> This has been an on and off debate I've had with myself and others, 
> and wanted some input from others. Input from live experiences is 
> great, input from low-level devs is even better.
> When RAM never seemed adequate for a system in the past, the utility 
> of swap was obvious. You would see the spikes on top(1) when swap was 
> hit.
> swap = 2 x RAM, blah blah.
> Today, when those 64G or more of RAM are the norm for bare-metal 
> boxes, and it's overkill in many contexts, is swap still necessary?

i'll bust out the only true answer in engineering...it depends :)

one use-case for swap for me personally is saving core dumps via 
safecore and friends on freebsd.  for this allocating a 2gb partition to 
swap is fine for my purposes.

the anti-pattern would be on any production system where i *never* want 
to swap out anything for both performance and security reasons.

it's funny though, i can't remember when i've had swap save me from a 
binary with run-away memory consumption in the past decade at least.  
frankly by the time chrome/slack decide that it needs 3/4 of my 32gigs 
of ram it's game over anyway.

ultimately i think if we had better OOMKiller functionality on linux, or 
better mechanisms in userland to manage and monitor memory over 
subscription and run-away processes in the general case, we could 
probably be done with swapping entirely.

just my 2 bits,

Pete Wright
pete at nomadlogic.org

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