[HEADS-UP] Rawhide: /tmp is now on tmpfs

[Jef Spaleta]

On Fri, Jun 1, 2012 at 7:05 AM, Gregory Maxwell <gmaxwell at gmail.com> wrote:
> Thats not true (and I've used tmpfs for tmp for years, so I'm speaking
> from experience)— tmpfs is backed by swap on demand. Just add the
> space that you would have used for /tmp to your swap.


I am _very_ concerned about large files in conjunction with tmpfs
usage for general purpose /tmp  by default. Especially on multi-user
capable systems.

As a sysadmin...for a multi-seat configuration in a home network
environment...do I really need to anticipate maximum large file tmp
usage in calculating my swap partition size for my multi-user family?
8 gigs of ram... so to be safe I want to set up a swap of what...100
gigs to account for a potentially large /tmp of some maximum size?


Does swap backed tmpfs as /tmp currently jeopardize my system's health
by making swap backup for in-memory processes compete with tmp files?
If my users clog up /tmp will that reach a point where the kernel's
oom process killer decided to start killing off running processes
instead of throwing crap out of /tmp?

What happens when I have 2 users who are both downloading dvd iso
sized images into /tmp  as well as other things going on. Remind me...
where does firefox by default cache in progress downloads for the
"Open in" facility. Isn't it down in tmp?   Do I really want things
like firefox downloads paging out ram into swap and causing an overall
system slowdown?

Without more information about how gracefully /tmp spill over into
swap is handled, I'm inclined to say this really looks problematic as
a default.
And that's not even getting into the more complex issues of virtual
machine configurations which typically run under heavier ram
constraints than disk constraints.


-jef