Re: Is swap == 2 * RAM a permanent thing?

[Mike Harrold]

> The reason is that the Linux 2.4 kernel no longer reclaims swap
> space on swapin (2.2 reclaimed swap space on write access, which
> lead to fragmented swap space in lots of workloads).
> 
> This means that a lot of memory ends up "duplicated" in RAM and
> in swap.
> 
> I plan on doing some code to reclaim swap space when we run out,
> but Linus doesn't seem to like that idea very much. His argument
> (when you're OOM, you should just fail instead of limp along)
> makes a lot of sense, however, and the reclaiming of swap space
> isn't really high on my TODO list ...
> 
> OTOH, for people who have swap < RAM and use it just as a small
> overflow area, Linus' argument falls short, so I guess some time
> in the future we will have code to reclaim swap space when needed.

I have some questions on this.

1) If a process uses swap space and then later (after being paged
   into memory -- or even not) it completes, is killed, etc., is
   the swap space reclaimed then?

2) If a process uses swap, is paged into memory, and is then swapped
   out again, does it re-use the same swap as before?

If the answer to either question is no, then IMHO, that's a pretty
serious design flaw.

Regards,

/Mike