Re: [ck] Re: 2.6.16-ck3

[Con Kolivas <kernel@kolivas.org>]

On Sunday 02 April 2006 18:51, Con Kolivas wrote:
> On Sunday 02 April 2006 14:46, Nick Piggin wrote:
> > The swap prefetching here, and the one in -mm AFAIKS still do not follow
> > the lowmem reserve ratio correctly. This might explain why prefetching
> > appears to help some people after updatedb swaps stuff out to make room
> > for pagecache -- it may actually be dipping into lower zones when it
> > shouldn't.
>
> Curious. I was under the impression lowmem reserve only did anything if you
> manually set it, and the users reporting on swap prefetch behaviour are not
> the sort of users likely to do so. I'm happy to fix whatever the lowmem
> reserve bug is but I doubt this bug is making swap prefetch behave better
> for ordinary users. Well, whatever the case is I'll have another look at
> lowmem reserve of course.

Ok I can't see what I'm doing wrong.

here are my watermarks

idx = zone_idx(z);
ns->lowfree[idx] = z->pages_high * 3 + z->lowmem_reserve[idx];
ns->highfree[idx] = ns->lowfree[idx] + z->pages_high;

It's (3 * pages_high) +lowmem_reserve which is well in excess of the reserve 
so I can't see any problem. Am I missing something?

Cheers,
Con