[ale] Ram, sigstop, swap, pids, etc

[Solomon Peachy]

On Mon, Feb 08, 2021 at 02:13:55PM -0500, Jim Kinney via Ale wrote:
> Will the kernel move Bob's process from ram to swap and back if it 
> sits in STOP for a while (hours to days)? Unknown how long after Mary 
> starts that it eats all the RAM.

It won't automatically move Bob's process to swap in one fell swoop; 
instead as Mary's process needs more RAM, Bob's will get incrementally 
paged out as it's not actively being accessed.

And when Mary's is finished, once Bob's is allowed to resume, it will 
get incremetnally paged back in as its components are needed.  (There's 
probably a tunable or other mechanism to "encourage" it to page back in 
more quickly, beyond running swapoff and forcing everything back..)

Performance is going to suffer while the paging is happening.

Perhaps a better option is the explicit checkpoint/restore mechanism using
the criu tool.

 - Solomon
-- 
Solomon Peachy			      pizza at shaftnet dot org (email&xmpp)
                                      @pizza:shaftnet dot org   (matrix)
High Springs, FL                      speachy (freenode)
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