[Devel] Re: [PATCH 8/8] Per-container pages reclamation

[Andrew Morton]

On Thu, 31 May 2007 14:35:43 +0400
Pavel Emelianov <xemul at openvz.org> wrote:

> > Would I be correct in guessing that pages which are on the
> > per-rss-container lists are also eligible for reclaim off the traditional
> > page LRUs?  If so, how does that work?  When a page gets freed off the
> 
> Yes. All the pages are accessible from booth - global and per-container
> LRU lists and reclamation can be performed from booth.
> 
> > per-zone LRUs does it also get removed from the per-rss_container LRU?  But
> > how can this be right?  
> 
> I don't get your idea here.

If we have a page which is on the zone LRU with refcount=1 and someone does
put_page() on it, we will take that page off the zone LRU and then actually
free the page.

I am assuming that your patches change that logic so that we will also
remove that page from the per-container LRU at the same time?

If so, the problem which I see is that, under rare circumstances, that
final put_page() will occur from interrupt context.  Hence we would be
trying to remove the page from the per-container LRU at interrupt time. 
But the locks which you have in there are not suited for taking from
interrupt context.