Re: Respin: [PATCH] mm: limit lowmem_reserve

[Con Kolivas <kernel@kolivas.org>]

On Thursday 06 April 2006 13:40, Andrew Morton wrote:
> Con Kolivas <kernel@kolivas.org> wrote:
> > On Thursday 06 April 2006 12:55, Con Kolivas wrote:
> > > On Thursday 06 April 2006 12:43, Andrew Morton wrote:
> > > > Con Kolivas <kernel@kolivas.org> wrote:
> > > > > It is possible with a low enough lowmem_reserve ratio to make
> > > > >  zone_watermark_ok fail repeatedly if the lower_zone is small
> > > > > enough.
> > > >
> > > > Is that actually a problem?
> > >
> > > Every single call to get_page_from_freelist will call on zone reclaim.
> > > It seems a problem to me if every call to __alloc_pages will do that?
> >
> > every call to __alloc_pages of that zone I mean
>
> One would need to check with the NUMA guys.  zone_reclaim() has a
> (lame-looking) timer in there to prevent it from doing too much work.
>
> That, or I'm missing something.  This problem wasn't particularly well
> described, sorry.

Ah ok. This all came about because I'm trying to honour the lowmem_reserve 
better in swap_prefetch at Nick's request. It's hard to honour a watermark 
that on some configurations is never reached.

Cheers,
Con