Supporting overcommit with the memory controller

[Pavel Emelyanov]

>>  Can Balbir's soft-limit patches help ?

[snip]

> 
> Yes, that could be a useful part of the solution - I suspect we'd need
> to have kswapd do the soft-limit push back as well as in
> try_to_free_pages(), to avoid the high-priority jobs getting stuck in
> the reclaim code. It would also be nice if we had:

BTW, one of the way OpenVZ users determine how much memory they
need for containers is the following: they set the limits to
maximal values and then check the "maxheld" (i.e. the maximal level
of consumption over the time) value.

Currently, we don't have such in res_counters and I'm going to
implement this. Objections?