Re: RSS Limit implementation issue

[Alan Cox <alan@lxorguk.ukuu.org.uk>]

On Iau, 2006-02-09 at 15:10 -0600, Ram Gupta wrote:
> I am working to implement enforcing RSS limits of a process. I am
> planning to make a check for rss limit when setting up pte. If the
> limit is crossed I see couple of  different ways of handling .
> 
> 1. Kill the process . In this case there is no swapping problem.

Not good as the process isn't responsible for the RSS size so it would
be rather random.

> 2. Dont kill the process but dont allocate the memory & do yield as we
> do for init process. Modify the scheduler not to chose the process
> which has already allocated rss upto its limit. When rss usage
> fallsbelow its limit then the scheduler may chose it again to run.
> Here there is a scenario when no page of the process has been freed or
> swapped out because there were enough free pages? Then we need a way
> to reschedule the process by forcefully freeing some pages or need to
> kill the process.

That is what I would expect. Or perhaps even allowing the process to
exceed the RSS but using the RSS limit as a swapper target so that the
process is victimised early. No point forcing swapping and the RSS limit
when there is free memory, only where the resource is contended ..