Re: Per-user swap devices.

From: Ian Stirling
Date: Wed Jul 19 2006 - 14:40:36 EST

Valdis.Kletnieks@xxxxxx wrote:
On Wed, 19 Jul 2006 10:54:38 BST, Ian Stirling said:

It would be really nice to be able to simply: chown crashalot.users /dev/swap0 ;swapon /dev/swap0
Then anything run by crashalot would swap to /dev/swap0 - and not locally.

This doesn't look like it will do as much good as you think. The problem
is what to do when something run by some *other* UID needs a page - you need
to fix the code to preferentially steal a page from a 'crashalot' process.

And at that point, what you probably want instead is a global per-UID RSS
limit. This looks like a job for a CKRM resource class controller rather than
a hack to the swap code.

Not quite.
I've got one set of users that I care about their processes never dying
root, ..., and another set that I don't.

I want them to contend for real RAM as normal - it's quite acceptible to me for users in the second group to push root/...s web-proxy, screen session, processes far into slow local swap. Most of these processes will be not very interactive - but I don't want them to die.

If the fast (but unreliable) swap device dies - I'm quite happy for my firefox and mplayer processes to die - but not my window manager or whatever. RSS limits don't address this.

The only way I can think of to address this is to somehow segregate swap devices.
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