On Wed, 25 Jul 2007 23:33:24 -0700 "Ray Lee" [off-list ref] wrote:

quoted

So.  We can

a) provide a way for userspace to reload pagecache and

b) merge maps2 (once it's finished) (pokes mpm)

and we're done?

Eh, dunno. Maybe?

We're assuming we come up with an API for userspace to get
notifications of evictions (without polling, though poll() would be
fine -- you know what I mean), and an API for re-victing those things
on demand.

I was assuming that polling would work OK.  I expect it would.

If you think that adding that API and maintaining it is
simpler/better than including a variation on the above hueristic I
offered, then yeah, I guess we are. It'll all have that vague
userspace s2ram odor about it, but I'm sure it could be made to work.

Actually, I overdesigned the API, I suspect.  What we _could_ do is to
provide a way of allowing userspace to say "pretend process A touched page
B": adopt its mm and go touch the page.  We in fact already have that:
PTRACE_PEEKTEXT.

So I suspect this could all be done by polling maps2 and using PEEKTEXT. 
The tricky part would be working out when to poll, and when to reestablish.

A neater implementation than PEEKTEXT would be to make the maps2 files
writeable(!) so as a party trick you could tar 'em up and then, when you
want to reestablish firefox's previous working set, do a untar in
/proc/$(pidof firefox)/

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