Re: [RFC 0/3] Recursive reclaim (on __PF_MEMALLOC)

Peter Zijlstra
2007-08-14T19:33:24Z

On Tue, 2007-08-14 at 08:29 -0700, Christoph Lameter wrote:
> On Tue, 14 Aug 2007, Peter Zijlstra wrote:
>
> > On Tue, 2007-08-14 at 07:21 -0700, Christoph Lameter wrote:
> > > The following patchset implements recursive reclaim. Recursive reclaim
> > > is necessary if we run out of memory in the writeout patch from reclaim.
> > >
> > > This is f.e. important for stacked filesystems or anything that does
> > > complicated processing in the writeout path.
> > >
> > > Recursive reclaim works because it limits itself to only reclaim pages
> > > that do not require writeout. It will only remove clean pages from the LRU.
> > > The dirty throttling of the VM during regular reclaim insures that the amount
> > > of dirty pages is limited.
> >
> > No it doesn't. All memory can be tied up by anonymous pages - who are
> > dirty by definition and are not clamped by the dirty limit.
>
> Ok but that could be addressed by making sure that a certain portion of
> memory is reserved for clean file backed pages.

Which gets us back to the initial problem of sizing this portion and
ensuring it is big enough to service the need.